I don't have a service engine light on and the code scanner didn't pick up any codes. My car has a slight misfire especially when it is cold. It still has it once warmed up but not as noticeable. When accelerating normally, the car will jerk a little and I guess its misfiring. The jerking is similar to being in too low of a gear... but I'm at 2000rpms when this happens. (The car IS a manual trans. by the way.) It could be an electrical misfire or a mechanical fuel issue. I don't know what the problem is. I was thinking that maybe it was the throttle position sensor or an oxygen sensor. But wouldn't those two throw a code? MAF sensor has been replaced 6 months ago so it shouldn't be that. Also has a new fuel filter and the injectors were cleaned too. Any suggestions?

 

i know its a pain but u should try replacing the plugs and wires it worked on my car and i didnt get a code until it got real bad hope that helps

 

Ok so I just put new plugs in it but not wires... The old plugs looked pretty bad. Very strange though, now the surge / misfire has become much much more noticeable. And it's also definately caused by putting a load on the engine. Coil pack?? If I rev the engine in neutral, everything seems alright. However, it does have a slightly rough idle. (no rough idle prior to new plugs) If I accelerate slowly then everything seems alright. But if I accelerate a little fast, it starts to surge / misfire and if I give it nearly full throttle it gets worse. Weak coil pack? Bad wires? Knock sensor? How can I test a coil pack individually? I don't want to have to buy all 3 coil packs. AND WHY THE HELLL AM I NOT GETTING ANY TROUBLE CODES????

 

I would suggest wires. As for no trouble codes... I am not sure. I have had symptoms like yours and new plugs and wires fixed it.

 

Replace the wires as 02StangGT suggested& if still bad get the coils and ignition module (under the coils)tested. All ignition stuff deteriorates with age. If ignition is good it is time to check the fuel delivery, and for mechanical problems.

 

I hate to sink too much money into it without pin-pointing out the exact problem. I checked the secondary resistance on all three coil packs and they checked out fine. I haven't checked the primary resistance yet b/c it is much more involved. I will check that soon and report back.

 

Always start with the easiest problem. You've already jumped that gun and started looking at coils. Those wires are most likely at the point of no return. Go ahead and put a set of AC Delco wires on them. Even if that is not the problem, a little PM never hurt anyone.

 

So after putting a new set of wires on it and little bit more driving around, I think it is more fuel related than ignition related. I talked with some other people and they suggest running a bottle of fuel injection cleaning through it or maybe replacing the idle air control. I'm still researching and working on it...

Just to restate the problem: Under a load / semi-hard acceleration, the car will jerk/surge very noticeably for about 3-5 seconds. If I let off the throttle and ease back into it, everything is ok. If I accelerate normally/slowly, everything is ok. Reving in neutral, everything is ok. ONLY under a load does it happen. No matter what gear or throttle range, a load will cause it to surge...

 

Actually... It somewhat sounds like your MAF sensor is going out... But I doubt it...

 

Right. Your car misfires under load. Revving in neutral is not a load. The engine is pulling no weight, therefore no load. Gather your resources and think of what senses load or what has to do with load. When there is a load on the engine, spark output is increased and advanced. Anything related to ignition could be questioned here, from plugs to coils to the module. Next, your have your load sensing devices such as the MAF/MAP.