Random "misfire"
04-12-2007, 08:59 PM
#1
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Random "misfire" 1999 z28, 53k. A few thousand miles ago it started "misfiring". Not throwing a code, but you can feel the hesitation/jerking/skipping, definite loss of power, and at/around idle it pops out the tailpipes. Not as loud as a backfire, just pops.
When this first started happening, it would only happen after I tached higher than 4k and then wouldnt go away. If I cut the car off and left it overnight, sometimes it would go away and other times it wouldnt. Now it happens pretty much from 5 min after startup to until I cut it off.
I know this is not an engine problem since it doesnt happen all the time. I know it is not the crank sensor because I replaced that. I am going to check the plugs next week when I get a spare moment, but I doubt that is the problem since they were replaced at 37k. The only other suggestions I have gotten are cam sensor (since it detects misfire, but no code so Im not sure), o2 sensor (acted like this when I fouled one out before, but no code) and PCM. Really dont want to replace that right now.
Has anyone else had this problem? This is my daily driver, and it is really starting to get on my last nerve. Cash is pretty tight right now, and I cant afford to play guess the diagnosis.
When this first started happening, it would only happen after I tached higher than 4k and then wouldnt go away. If I cut the car off and left it overnight, sometimes it would go away and other times it wouldnt. Now it happens pretty much from 5 min after startup to until I cut it off.
I know this is not an engine problem since it doesnt happen all the time. I know it is not the crank sensor because I replaced that. I am going to check the plugs next week when I get a spare moment, but I doubt that is the problem since they were replaced at 37k. The only other suggestions I have gotten are cam sensor (since it detects misfire, but no code so Im not sure), o2 sensor (acted like this when I fouled one out before, but no code) and PCM. Really dont want to replace that right now.
Has anyone else had this problem? This is my daily driver, and it is really starting to get on my last nerve. Cash is pretty tight right now, and I cant afford to play guess the diagnosis.
04-13-2007, 10:25 AM
#4
What he said, Start with the easy stuff. Wires and connections. Air filter, look at all the basics first. Dont wait to check the plugs just get out and do it. They might tell the whole story.
IS it an auto or a standard? Maybe it isnt the engine at all if your not getting a code. Auto's can feel real wierd when they start going. Standards will rev so you would notice that I would think.
IS it an auto or a standard? Maybe it isnt the engine at all if your not getting a code. Auto's can feel real wierd when they start going. Standards will rev so you would notice that I would think.
04-17-2007, 06:50 AM
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Checked the air filter, replaced the crank sensor, swapped maf's, and cleaned the ground all after this started.... No recent mods, everything looks fine diagnostic-wise, and it is a manual.
Two things I forgot to mention. First, the SES light comes and goes as it pleases. Second, I had a friend at a local performance shop check it out, and he put some tool up to each coil pack.... 7 and 8 were firing erratically while the others were firing consistantly. This is why I doubt it is plugs, but I am changing those this week anyways. Something is more than likely telling the coils to fire like that, and 7 and 8 are also right next to each other in the firing order.
I am so fed up with dealing with the last owner's f*ck ups I could scream. I have spent thousands of dollars fixing things that he abused in the year that he owned the car, and I shouldnt have to do that with a bolt-on car that only has 53k on the clock............
Two things I forgot to mention. First, the SES light comes and goes as it pleases. Second, I had a friend at a local performance shop check it out, and he put some tool up to each coil pack.... 7 and 8 were firing erratically while the others were firing consistantly. This is why I doubt it is plugs, but I am changing those this week anyways. Something is more than likely telling the coils to fire like that, and 7 and 8 are also right next to each other in the firing order.
I am so fed up with dealing with the last owner's f*ck ups I could scream. I have spent thousands of dollars fixing things that he abused in the year that he owned the car, and I shouldnt have to do that with a bolt-on car that only has 53k on the clock............
