A faulty computer may cause the vehicle to intermittently have issues such as stalling or misfires. The misfire would come and go and has been getting worse. In many instances, stalling ends up being an idle control motor at its limit or a failed motor. If misfire happens only at idle, the EGR valve and purge valve need to be checked, as either one could be stuck open. Hi, guys I am rebuilding a v8 for my crackerbox build and have bought a lot of chrome parts one of witch is a crossover pipe at the top of the photo that goes in place of the water pump, dose that mean I can run the engine and cool the 1-1 gearbox off the raw water pump and do away with the circulating pump. Symptoms of a Misfire. Chevy Suburban 1500 Engines. I have a misfire on cylinder number 2. 3L engine, the info easily applies to any CSFI 'Spider' equipped 4. or when trying to rev the engine while standing still for that matter. One way to detect a misfiring engine is by sensing the Corvette's engine. For a cylinder misfire problem, you need to change components, such as coils, spark plugs, etc. [email protected] FIXED! 1998 chevy k1500 5. I hooked up a obd II scanner to the computer and it said cylinder #8 misfire. I had a couple threads over a year ago about my 229 V6 idle vibration nothing seemed to affect it. 7 350 in it and it is running really sluggish and is having misfire, service engine soon light is on. As far as bad compression is concerned, bad lifters could possibly be the cause as a delayed valve opening/closing function could cause poor combustion sealing. Is this a completely stock '79 350?. Re: 350 chevy swap to an 2002 wrangler ? It would take you a lot of years to recoup the money that it would cost you to change over to a 350. In most four-cylinder engines the numbering is 1-3-4-2 while in the Chevy 350 small block engine the firing order is 1-8-4-3-6-5-7-2. P0303 is a generic diagnostic trouble code (DTC) indicating an issue with the firing of cylinder 3. Msifres bad under acceleration. If it hasn't been knocking, it doesn't seem to have the starting issue, and vice versa But, could be coincidence. If EGO correction is active under those conditions, this will result in an even richer mixture, and worse misfiring, etc. An ignition misfire can be consistent (all of the time) or it can come and go (intermittently misfire). 2 comments. Choose Group to View Cylinder Head Codes Select Cylinder Head Group ALL Head Codes 262, 265, 267 302, 305 or 307 302 Only 327 350 400. That P0302 can also be a the coil and plug. I have a 1998 Chevy 1500 Vortec 5. Chevrolet Infotainment System functionality varies by model. Chevy Suburban 1500 Engines. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon. 7 Vortec that I think I’ve figured out. If you happen to need a distrib. diagnosing misfires Misfire is a common driveability problem that may or may not be easy to diagnose, depending on the cause. i have checked plugs, plug wires, crank sensor, and and coil. I have been working on trying to find what's causing it. Chevy Forums FREE technical assistance for your restoration and repair. most of the older 305 had bad camshaft wear. I have changed the spark plugs and spark plug wires and the distributor cap and the fuel filter. The ugly truth behind grid-tie solar systems. 510 lift roller cam 1. A faulty sending unit will not enable the dash. The engine idles very rough and you can definitely tell it's a misfire from the exhaust end. 7 Vortec that I think I’ve figured out. Valve adjustment may need to be checked, as valves that are out of adjustment can cause misfiring at a cold start, which is, a fairly common issue in some older Honda engines. they should both fluctuate within 10% of zero. The time now is Sun Aug 18, 2019 8:32 am 1997 Chev ECSB L31 350 1997 GMC. When the engine warms up though, the misfiring occurs. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc. i have a 2000 chevy k2500 with a vortec 350. If the timing chain was the issue it would be random misfire, not limited to 1 or 2 specific cylinders. Chevy Check Engine Light Codes. It doesn't seem like it is affecting anything cause it drives fine and revs really fast. I have a Chevy K1500 sierra with a 350 that is not EFI. It is a 91 chevy truck with the 350 (5. One week after putting a new set of AC Delco plugs in it, it. It has done this 6 times in the past month. The 2007 Chevrolet Suburban has 12 problems reported for stabilitrack light on, oil loss, misfire, oil soaked plug. I am trying to tune out a hesitation in the off idle part throttle range. How can you get 350 horsepower out of a 305 Chevy small block? Your car's warning display or an OBD reader shows that a cylinder is misfiring. 3L engine, the info easily applies to any CSFI 'Spider' equipped 4. drove it home about 15 miles spitting and sputtering up every hill. Chevrolet Silverado 1999-2006: Common Noises Diagnostic. Learn about this problem, why it occurs, and how to fix it. I just thought of something else. 00 trying to find the problem for this. Idle ok when misses when reving and accelerating. Fuel and air comes from the fuel system and carburetors. Engine Stalls, Misfire Code, & Cylinder Misfire The engine may be stalling because it isn't getting enough throttle opening. I have a 2008 Chevy Silverado 5. Typically, cylinders 3,4,5 or 6 will be the ones to experience this. This may be the result of an AFM (Active Fuel Management for displacement-on-demand) lifter that unlocks as soon as the engine is started or one that is mechanically collapsed/stuck. Another symptom of a bad or failing ECU is erratic engine behavior. It does it sometimes at idle when cold and does it just going down the road at 40-45mph when it gets into overdrive and is running in the 1500RPM range. Ok so i have my car tuned up pretty well, ignition timing at about 12 degrees, brand new plugs and wires. If misfire happens only at idle, the EGR valve and purge valve need to be checked, as either one could be stuck open. What would cause this? - Answered by a verified Chevy Mechanic. The truck doesnt run right at all. It has a jasper motor with 10000 miles on it. 1-800-575-6998 Overseas 1-443-451-5139. Also, make sure you jot down the other codes, as misfire can be caused by a malfunctioning component or system. They do not know the cause. 7 Vortec with a misfire, P0300 code for 3 months. 1999 chevy 350 runs rough at idle. 7 TBI intermittent poor idle/slight misfire - Chevy Message Forum - Restoration and Repair Help. MISFIRE and TROUBLESHOOTING the ENGINE - CF-106. While General Motors had to make some compromises in the initial design, the result is an engine that older car owners can tune to a "sweet spot" between horsepower and fuel efficiency. I started developing a misfire every once and a while. The starting point of your Misfire or No-Start diagnosis is testing for spark at the spark plug wires. so once again I am having issues with my TBI 350. Hi, guys I am rebuilding a v8 for my crackerbox build and have bought a lot of chrome parts one of witch is a crossover pipe at the top of the photo that goes in place of the water pump, dose that mean I can run the engine and cool the 1-1 gearbox off the raw water pump and do away with the circulating pump. I had the fuel filter replaced and the previous owner said the fuel pump is almost new. The eight cylinder Chevrolet 305 is poorly regarded because of poor factory performance, especially when compared to Chevy's larger 350 engine. Its also possible you lost 1/2. P0302 is a cylinder specific misfire code, which means that cylinder 2 is misfiring and causing the code. Engine running trouble with Chevy 350 I noticed that the engine was running a little rough and figured that it was misfiring from a set of fouled plugs or. I have a misfire on cylinder number 2. This misfiring only happens when the connector used to set the 'base timing' is plugged together. Learn what does P0300 Chevrolet Cylinder Misfire Detected Random Cylinders means, location and how to repair? When a misfire occurs, engine speed will fluctuate. Full functionality requires compatible Bluetooth and smartphone, and USB connectivity for some devices. Why is there Misfiring on load 1987 Chevy truck 350? Need to check spark plug wires and the plugs, I would say you just need a good tune-up. the engine stumbles bad. Shop with confidence. And everytime we tried it it would say cylinder 6 misfire. Ford Triton V8 firing order The plug numbers and firing order on the Ford Triton engine with aluminum heads. I have a 1999 Chevy Tahoe, 5. So, I complained on here in June about how my car was being a pile of junk! (literally!) 2009 Chevy Malibu 58,200 miles Anyway, the "jerking" or as the mechanic told me, MISFIRING, had gotten worse. 3L Engine 4WD 234,000 Miles Symptoms: When accelerating, upon reaching about 1500 RPM through about 2250 RPM the engine misfires in first gear (occasionally 2n. I drove this SUV for a few miles with no issues. Put gas in ran fine for about 3-4days then just started getting sluggish, loss power, some backfiring when you try to jump on it. I've "looked" for vacuum leaks but came up with nothing but I still need to try the propane torch idea. That is what sets a no activity code as the 02 sensor will read a lean condition due to the misfire. It started with the engine light being on for a while, with a slightly rough idle but otherwise ran great. There was a crack in the intake, leaning out that side of the manifold enough to misfire. 1999 Yukon - Finally fixed misfire under load at 70 mph Yukon Car Forums I've got the Chevy techs baffled as to why it is happening, so I may give this a shot. Problem with my 1998 Chevy k1500 5L V8 305. The time now is Sun Aug 18, 2019 8:32 am 1997 Chev ECSB L31 350 1997 GMC. A faulty computer may cause the vehicle to intermittently have issues such as stalling or misfires. I don't know how many miles are on the motor. Repair Information for P0300 Chevrolet code. I have a 1999 Chevy Tahoe, 5. Ignition misfire. 2002 Chevy 1/2 ton truck. 7/auto, used short block with fresh heads installed 25K miles ago - those of you that followed the project may remember I replaced a ton of items as well to ensure its reliability. Tracking down the issue of why your C5, C6 or C7 engine is misfiring is not easy. Topics included in this article include - Introduction to the Problem; Advice We Have Received Regarding Our "Hesitation" Problem. In some cases, it is the catalytic converter that causes the misfiring. The P0303 DTC is set when the ECU detects multiple misfires from cylinder 3. What is misfiring and what are the causes of misfiring? In order for a cylinder to fire properly, it needs 4 things all working together: Proper Fuel/Air. It has a misfire at idle and a very random misfire while driveing. The loss of 25% of the engine's power output is the equivalent of a horse trying to run on three legs. A misfire can sometimes be an indication of a burned exhaust valve. Typically, cylinders 3,4,5 or 6 will be the ones to experience this. All good til about 120,000 when it did the same thing. 7l has a code p0300 random misfire what code this be? asked by Demario G on September 11, 2017 My engine light came on and is said it was a code p0300 random misfire what could this be?. Engine running rough or misfiring can be cause by the following-inspect and test all the following listed below: 97 Chevy 350. If the spark plug wire for. Diagnosing Misfires Download PDF. I have change out the following parts: 1) air filter. Mileage may suffer as well when your Silverado has P0302. 11 gears, an MSD 6AL ignition box, Mallory Unilite distributor, Powermaster alternator, Moroso electric water pump, Holley electric fuel pump, and an electric fan. Bad compression can also be failing piston rings and leaking valve seats. GMC, Chevrolet). One week after putting a new set of AC Delco plugs in it, it. Chevy 350 5. The sensible method is to gather available knowledge about the engine misfire, focus on steps necessary to eliminate suspects and let the process guide you to its cause. The engine usually feels rough, lacks power and uses more gas than usual. GM Performance Forum Index » GM Performance Forum » Finally fixed my random misfire. Hello, I have a 1997 chevy k1500 with the 5. 01-07-12 04:51 PM - Post# 2176787 This is the girlfriend's '93 C1500 5. If the engine speed fluctuates enough to cause the Crankshaft Position sensor signal to vary, the Engine Control Module can determine that a misfire is occurring. I have an aftermarket chevy 350 engine in my 68 camaro. New Quality Hand-Built in America Chevy 350 Small Block Engines for Sale for Your Street Performance Hot Rod, Muscle Car, or Classic Truck! Available in Short Block, Long Block, and Custom Crate Engine Packages. This is designed to make sure there's no gap when it's plugged into your Chevy 350 engine, which prevents the risk of erosion. This is because of the higher demand for spark. 5 roller rockers 305 Ho heads edelbrock 600 cfm carb) has developed a bad misfire under hard accel. remove valve covers. Good afternoon, I have what may be a stupid question but how do you go about. The Malfunction Indicator Lamp (MIL) is on and you've just found a misfire code. The engine usually feels rough, lacks power and uses more gas than usual. i have replaced cap, rotor, plugs and wiresand it has 175 pounds on all cylinders. ****read****1991 chevy 2500. Spark comes from the ignition system. The distributor also disburses current. Welcome to the Chevy Check Engine Light codes page. Sometimes a misfire may feel like a vibration. The "soft" misfire, often called a surge, is commonly associated with fuel related issues. I just got done swapping out the motor with a low mileage one that i saw running before I pulled it. Chevy 350 5. It also got better fuel economy, making it a worthy successor to the long-lived small block Chevy. Drives great with good power and gets decent gas mileage. With the spark throwers and spark carriers cleared of responsibility for code P0304, we moved along to the spark makers. Raw fuel is also passing through the cylinder into the exhaust. Mainly uphill you have to put the foot down to maintain speed and the exhaust roars (dual 3” that I will replace if I get it to work properly). If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. The 2007 Chevrolet Avalanche has 9 problems reported for engine misfiring. It is SO sensitive and accurate, that the system can determine EXACTLY which cylinder is misfiring and how much it is misfiring compare to the other 7 cylinders. I have a 98 Chevy 1500 with a 5. Driving with a misfire can damage that catalytic converter. Okay I'm done throwing money away I can't solve this one what I have already replaced: fuel pump and filter, spark plugs and wires, Cap and rotor, fuel injector lines checked for vacuum leaks w car. Just can't do it. If you happen to need a distrib. if its the camshaft you will notice little movement on the rocker arm. The first sign of the problem was the service engine light would blink intermittently when driving on the highway or revving the gas. The problem that I seem to be having is the truck misfires at idle only. I had a diagnostic and they told me on my 94 Chevy Blazer that it was my EGR Valve. 7 ltr #8 cylinder misfire I have 98 Chevy 1500 5. drove it home about 15 miles spitting and sputtering up every hill. In any event, a random misfire means the engine has multiple cylinders that are misfiring at random intervals. Although this case study is about my neighbor's 1995 Chevy Blazer with a CPI equipped 4. Diesel engine surging at low speeds. At 65mph, when you hit the gas hard, it sputters, no power, check engine light starts blinking, feels like an injector is not working. Dec 12 2011, 1:47am. I have a 98 chevy 1500 5. Engine running trouble with Chevy 350 I noticed that the engine was running a little rough and figured that it was misfiring from a set of fouled plugs or. Engine Stalls (Check Engine Light May or May Not Be On). Hi, guys I am rebuilding a v8 for my crackerbox build and have bought a lot of chrome parts one of witch is a crossover pipe at the top of the photo that goes in place of the water pump, dose that mean I can run the engine and cool the 1-1 gearbox off the raw water pump and do away with the circulating pump. After running the vehicle some I found that if I rev the engine up between 2500 & 3000 rpms, the mis goes away and the scanner data for misfire goes to 0 and the vehicle runs smooth. Chevrolet Vehicles Have Been Recalled 638 Times. I know however Advance Adapters make the AX-15 bracket for the 350 though. I shut off the truck and the problem went away but the check engine light stayed on and my dad. The engine runs fine when cold but as it warms up it starts to "surge" at idle and when you come to a stop it acts like it wants to stall then it grabs. It doesn't seem like it is affecting anything cause it drives fine and revs really fast. Inboard Marine Engine Center This remanufactured engine site has inboard longblock engines, turnkey engines, performance engine upgrades below and general information at links above. We swapped the QuadraJet iron intake for an Edelbrock aluminum Performer dual-plane intake at the same time we installed the Sniper (no ignition control). My 99 Chevy tahoe vortec 5. Most drivers will experience this issue at some point during their lives. The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. I have a 1998 Chevy 1500 Vortec 5. Idle ok when misses when reving and accelerating. 7) with TBI. , fuel that fails to burn because there is to much for the amount of oxygen available) can indicate a lean condition to the sensor (excess oxygen that was not burnt because of the misfire). A friend told me that it could be the timing chain is off a few marks or the valves are closing how they are supposed to. Hi, I am having a problem with my chevy 350 engine that I just installed back in August. Can almost 99% guarentee you will fix this problem with new wires, plugs and opti. The increase in the number of vehicles with automotive fuel pumps is enabling the robust growth of the fuel injector market, with electric fuel pumps responsible for driving this growth. I just put one in my Grand Prix switched from the 350 Chevy and with a 4 barrel holly carb you will notice a BIG difference. Fuel and air comes from the fuel system and carburetors. I have have been dealing with this P0171 diagnostic trouble code for many years on many different year make and model vehicles. Inboard Marine Engine Center This remanufactured engine site has inboard longblock engines, turnkey engines, performance engine upgrades below and general information at links above. Read more about this 1996 Chevy C1500 Pickup Catalytic Converter Misfiring Problem and get expert advice from the Truck & SUV expert Alex Steele at Truck Trend!. changed fuel pump relay, crank sensor, cam sensor and. New distributor cap and rotor. I did this on an old beater Nissan pickup I had and two cylinders that were at 120psi before ended up matching the others at 180psi after the service with a smoother idle. I have a '96 Chevy Tahoe 2 dr. I just bought a chevy truck, 76 with a 350, here in Reno theres a hwy 421, going to tahoe steep uphill as i entered the hill, the truck dropped down into second and after it went back into 3rd i had a backfire through the carb. I have a 98 chevy 1500 5. What does this code mean anyway? The definition for this this P0171 code is Fuel Trim System Lean (Bank 1). It started backfiring out of the carb when I rapidly throttle up. I had the fuel filter replaced and the previous owner said the fuel pump is almost new. Dec 12 2011, 1:47am. The truck doesnt run right at all. After that the misfiring was gone, the truck still felt a bit more sluggish than it should have been. I started developing a misfire every once and a while. What is misfiring and what are the causes of misfiring? In order for a cylinder to fire properly, it needs 4 things all working together: Proper Fuel/Air. Any ideas?. went to leave work 4hours later and instantly noticed a misfire under load above 1500 rpm. 002 of an inch just enough to create low compression and a misfire at idle but run. the engine stumbles bad. Get in the gas or out and it stops. The domain chacha. hey guys new to the group I have a freshly rebuilt Chevy 350, got it running yesterday but had some concerns, the timing was set dead on the distributor but it had a odd misfire. cap, rotor, plugs, wires, new fuel pump, and fuel filter. I have a misfire on cylinder number 2. Ive changed all the lifters,coils,in. I've "looked" for vacuum leaks but came up with nothing but I still need to try the propane torch idea. What the P0303 code means. runs a little rough, while driving under normal conditions it sputters, hesitates, and also will backfire, under heavy acceleration no noticeable skip, no sputters, and does not hesitate or backfire. Misfire is a common drivability problem that may or may not be easy to diagnose, depending on the cause. Requires compatible iPhone and data plan rates apply. This page will list all the Check Engine Light questions and answers asked of us pertaining to Chevy vehicles. Chevy/Chevrolet Check Engine Light Questions. Chevy Silverado P0302 Definition. Error Code P0303 is a common error code that indicates a misfire problem in the engine's cylinder, specifically cylinder #3. i tuned it up 3 months ago. An SBC comp cam is an integral part of an engine's internal combustion system, which enables the car to run. OK, I bought someone Else's problem. Diagnosing Misfires Download PDF. The Cheap rehab '79 Chevy truck is running pretty good, but still has a nagging misfire. This is designed to make sure there’s no gap when it’s plugged into your Chevy 350 engine, which prevents the risk of erosion. [email protected] 7 Liter 350 V8. The Chevy dealer says this is impossible to fix? take it back to him and have him tell you which cylinder is misfiring and under. Vortec 305 and 350 4x reluctor wheel The Vortec 350, RPO L31 is a Generation 1-Enhanced engine, AKA GEN 1-E, known as the Vortec engines, specifically that used the new CSFI(Central. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc. I have a mid 1970 chevy 350 it pops through the left side bank only @ a steady 2000 rpm. The truck only misses when under heavy load or going up a steep hill. Misfire in cylinder 8 C I have a 2000 Chevy Silverado 5. Symptoms of a Misfire. WHAT IS DETONATION? Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. 79 350 freshly rebuilt. It is a 91 chevy truck with the 350 (5. After I put on the extra ground wire and drove home, I noticed that it didn't chug as much, so I'm wondering, where are the ground wires located so I can replace them, ALL of them. My sugestion would be to buy a vehicle with better gas mileage and keep the jeep as a toy. gm forum at Car Dealer Forums; 1999 C1500 Suburban 350 Vortec - 86K - Started misfiring - Code P0300 - Engine. If it hasn't been knocking, it doesn't seem to have the starting issue, and vice versa But, could be coincidence. A while back I had bad misfiring (sputter, missing, and stumble) while accelerating and in the last gear under greater load i. 002 of an inch just enough to create low compression and a misfire at idle but run. Its also possible you lost 1/2. My truck seems to maybe be misfiring. P0303 is a generic diagnostic trouble code (DTC) indicating an issue with the firing of cylinder 3. FarmCraft101 1,304,367 views. The cause is often a problem in the idle air control system. mhamilton on Sun September 23, 2007 3:06 PM. I have had it for 1 year and. if its the camshaft you will notice little movement on the rocker arm. The best-known small block V8 in GM's stable, the Chevy 350 engine is considered one of the 20th century's best engines. After that the misfiring was gone, the truck still felt a bit more sluggish than it should have been. What causes an misfire in Chevy 350 engine? While an incorrect fuel/air ratio can cause a misfire, it's not likely to cause only one cylinder to misfire unless you have tuned port injection. The sensible method is to gather available knowledge about the engine misfire, focus on steps necessary to eliminate suspects and let the process guide you to its cause. It occurs around 2000-2500 rpm. 7 vortec misfire at idle. from what i can tell about it from what you have said,it may be off in the timing of it,this can make it do this a lot ,it only takes a few degrees to do this,even a little wear in the timing chain can cause this to happen,id start checking this stuff, i think the majority of it can be took out with the timing,good luck,i hope this help,s. We're not talking about a knocking engine or one that idles rough or stalls. Bad compression can also be failing piston rings and leaking valve seats. 2013 Black Granite Metallic Chevy Cruze ECO 6MT (Traded) The Tune sells for $350. It has a misfire at idle and a very random misfire while driveing. 3 horsepower. I figured this was caused by low-quality gas but it wasn't as it kept misfiring even when I put quality gas in. Have you ever solved a misfire problem? Tell us your solution and advice in the comments below! Shop for Tune-Up Parts. The 2007 Chevrolet Avalanche has 9 problems reported for engine misfiring. 7L (305 & 350 CID) crankshaft used in various GM cars. Select the navigation view. It is SO sensitive and accurate, that the system can determine EXACTLY which cylinder is misfiring and how much it is misfiring compare to the other 7 cylinders. - 2013 ES 350 with 29,000 miles to date. Chevrolet / Chevy Corvette Engine Information (305 & 350 CID) Crankshafts Identifying the Chevrolet 5. 7L Vortec 350 V8 engine. First, let's pinpoint exactly what's going on. Can someone please help with what I should check next, I have a 1998 Chevy K1500 5. Now what? Misfire diagnosis in this kind of situation should be fairly easy. You can get a photo by calling your local Chevy dealer service center and requesting one. I think the car is kinda sluggish, but this is also my first K5 and 350 so I have nothing else to compare to. This code may be seen with other misfire codes as well as lean / rich condition codes. Help with 98 Chevy 5. Welcome to the neighborhood! I know this sounds extremely simple, but check those misfiring cylinder plugs, make sure they are still fully seated in the head and that the wires are fully seated on the plugs and that the plugs aren't burnt, etc. Truck idles good when in park but when I put it into gear the check engine light comes on. 03-06-12 05:02 PM - Post# 2199334 I have a 1994 chevy c1500 with a v6 motor and for a while it's been misfiring pretty badly. I had experienced a slightly rough idle previously (nothing serious) and had been unable to track it down. 350 tbi has a bad misfire. Ford Triton V8 firing order The plug numbers and firing order on the Ford Triton engine with aluminum heads. Spark comes from the ignition system. Idle ok when misses when reving and accelerating. Problem with my 1999 Chevy Silverado 1500 5. unplug distributor power wire and have someone turn it over for ya. We're not talking about a knocking engine or one that idles rough or stalls. Shop with confidence. Get in the gas or out and it stops. 350 chevy missing on 2 cylinders in the same bank? I have a 350 chevy motor with a msd ignition and msd ignition box, new cap and rotor, new plug wires, new plugs. 1-800-575-6998 Overseas 1-443-451-5139. On 1996 and newer engines with OBD II and misfire detection, a coil failure will usually set a P030X misfire code where "X" is the number of the cylinder that is misfiring. went to leave work 4hours later and instantly noticed a misfire under load above 1500 rpm. 7 Vortec with a misfire, P0300 code for 3 months. I just put on new plugs,wires and also a rebuilt Q-jet. The truck has 190K miles on it and runs fine other than a misfire. Driving with a misfire can damage that catalytic converter. It is usually found on the top of the head in between two valves and the rocker arm studs. Also, make sure you jot down the other codes, as misfire can be caused by a malfunctioning component or system. A flashing check engine light and a P0301 to P0312 diagnostic trouble code (DTC) is a surefire indication that one or more cylinders are misfiring. The complaint on this Blazer was that it had a misfire that was bad enough to make the tach jerk. My 96 chevy 1500 4x4 with a 5. I think the car is kinda sluggish, but this is also my first K5 and 350 so I have nothing else to compare to. I have no idea what the codes were. I was wondering if a bad 02 sensor could cause a backfire.