I have been having a problem with my 1998 camaro with 120000 miles on it. The car started missing badly, too badly to drive and the shop ended up replacing one of the firing coils and the problem was fixed for about 1 month. Now the car idles fine and revs fine but when under any load over 2500 rpms it craps out and starts to hiccup and misses badly with the occasional backfire but when you let off it starts to run fine. So basically it drives normally under 2500 rpms. It was put in storage in a field and some mice nibbled some wires but they were taped up and fixed. I looked under the hood and the shop used the old rusty screws so i tooke them out, cleaned them up and put them back but to no aval. I took it for a spin and the first 3 min, It ran perfectly but the same problem happened so i spent all day under the hood fixing little things like a vaccum hose at the throttle body and fixing a chewed fuel injection wire that had been chewed. Im sure its electrical because i checked fuel pressure and changed the air filter. I own a car computer scanner and the only code it gave was a cylinder 5 misfire. Then i checked the fuel injector cable on cylinder 5 and it was fine. The only thing left i can think of it to clean the fuel injectors but my dad said that the car wouldent even idle if that were it. I ordered a new firing module and 3 new coils and I hope that fixes it. Any other ideas? Im very desprate[:@]

 

All the other sensors look ok, as far as wiring goes? Only things that come to mind are catalytic converter, crank sensor, or ignition module.

 

i've ordered a new module and 3 new coils and they should be here tommarow but the wires to the sensors are all ok. How would the catty be causing the miss? Ill check out the crank sensor.

 

If cat is plugged or partially plugged, exhaust has nowhere to go. Your car will then run like poo.

 

wouldent it not run good at any point then? you can drive it fine under a little pressure but under any sort of load it craps out
[align=right] [/align]

 

Does it do it when you are in neutral and rev it? I'm thinking that's what you meant by it idles and revs fine...

 

youd be right in thingking that it revs in park and neutral fine. as in no missing. then when ur under a load, and try to stomp on it a little it starts crappin out. but the pecular thing is that after it sits for a little, in the first 3 mins, it funs flawlessly no missing under any circumstances but come to a stop sign it just misses like it starving for either gas or air. when we took it the shop, they replaced the crank sensor, forgot to mention. If the new module and new coils dont do it then it might also be the temp sensors and the comp might think the engine is hot and be mixing lean. but as i think of this, it would have come up on the handheld scanner? when its missing the car feels like its starving, not being flodded. Thx for the help. i will know by tommaro night because the parts are on next day air and i ordered them on sunday. could the bad module be ruining the coils? when the shop replaced one of the coil packs, it worked for about a month and the same problem came up 4 days ago.

 

Fix the misfire first, when is the last time the spark plugs, and plug wires were changed? If your car runs OK when cold (open loop condition), and runs poorly when warmed up (closed loop condition), it is an indication that there may be a problem with one or more sensors. Especially since rodents had a goodtime with the wiring. Get some NOID lites and check that all injectors are being fired. Look at 02 sensor activity & make sure the voltage is cycling at a rapid rate.

The car will idle, although poorly,with a dead injector, as the computer will compensate by increasing the amount of idle air.

Also as 02StangGT mentioned, take a good look at the cat converter. If partially clogged it will affect engine performance under load, when more exhaust is produced, and will look OK when the engine is not under load, such as idling or revving it in neutral.

 

the plugs and wires were changed a month ago when i took it to the shop. there was a chewed o2 sensor and that got replaced also. the other o2 sensors are only a few months old.

 

Its all good now!!! the ignition was the prob and when i replaced the coil packs and module, it fired right up and works fine now!!! thx for all urguys help. im getting my provisionals and it REALLY would have sucked to not have my car to drive tommaro!!