Miss/exhaust backfire

[dragnazz5.0]

i used to be the same way but now i like to think that im pretty damn good with a meter and with electricity in general.

 

[noslow1986]

um i have the same problem mine happens when its cold and once it warms up its fine but i still have a miss a 4500 rpms almost like a rev limiter

 

[OrLackThereof]

Thanks guys I'll check it out in the next few days, see if I find something.

noslow...sure your tach is correct? And it only happens at that specific rpm, only when cold?

 

[noslow1986]

it happens when its warm and at 4500 rpms all the time

 

[OrLackThereof]

it happens when its warm and at 4500 rpms all the time

Check your MAF, I fixed a guy's car that did the same thing but at 3000 rpms, like a wall it wouldnt rev past, it was a faulty mass air meter.

Update guys: Driving to the movies today the miss got much, MUCH worse. Loud backfires in rapid succession, EXTREME bogging, kicking and bucking randomly all the way to the theater. On the way home, no such behavior only the normal symptoms, random popping in the exhaust.

Paying closer attention, during cruise, I can actually *hear* the explosions in the exhaust pipe, like for some reason fuel is getting in there and detonating from the heat. Which could explain why I dont hear it when its cold, it takes only a minute for the pipes to get hot.

 

[mob]

Sounds ALOT like my problems, im looking at a vacuum leak in the intake and bad valve stem seals in the heads.

You guys think maybe its possible valve geometry is off causing a vacuum leak? Just a thought, ill keep you updated on if I fix my problem, like I said, sounds exactly like yours. Do you notice any white smoke sometimes on SOME start ups?

 

[OrLackThereof]

Sounds ALOT like my problems, im looking at a vacuum leak in the intake and bad valve stem seals in the heads.

You guys think maybe its possible valve geometry is off causing a vacuum leak? Just a thought, ill keep you updated on if I fix my problem, like I said, sounds exactly like yours. Do you notice any white smoke sometimes on SOME start ups?

Thanks, Id be curious to know how yours goes. No smoke here, only very faint smoke on a hard rev..

Im so confused because these symptoms are contradicting themselves.... Only thing I can say for sure is, when I feel the power-cut (where its not making any noise, but the gas pedal is down and the motor is just not pulling)...and I add load to it, it gets worse. As the rpms increase it seems to start clearing itself out until it pulls clean, but not always.

 

[OrLackThereof]

Figured I would update those who were curious and tried to help me...it was MUCH appreciated, yall got my thought in different directions. Anyways I figured I would try to narrow it down to the open or closed loop systems, so I disconnected both O2 sensors and I'll be damned, it's cured. It idles differently, more consistent.....it drives much smoother, it has no misfire whatsoever, no backfiring whatsoever, and runs very good at any throttle position.

I've checked the sensors themselves, the O2 ground, the salt/pepper shakers...I suspect a wiring problem/short somewhere in the harness before it meets the ECU, somewhere behind the firewall, but I can't say for sure. All I know is that running on a stock fuel map, it runs beautifully, no pinging, not overly rich, and WOT is obviously the same as it was dyno-tuned for, so I really have no more modifications to make, other than removing the sensors completely and installing plugs in the bungs, and setting them upon a shelf.

Thanks for the help guys, this has been a LONG-TERM problem and I'm relieved beyond imagination for finally solving this...