i know ive been posting alot recently but i have a problem with my 305 TBI camaro RS that just wont go away. ill start with a list of replaced parts:
fuel pressure regulator
fuel filter
EGR valve
distrubtor cap and rotor
plugs
wires
collant temp sensor
car produces no check engine codes. car will also run fine some of the time. sometime it starts acting up reallly really bad. when you get on it tach will jump all over the place. it will wander up and down 500-1000 rpm or more, and the car will buck and hesitate bad. this is realy starting to p**** me off big time. sometimes its so bad i cant get the car over 30. its really embarrassing to have to put your hazards on and get passed by crappy four cylinder cars. sometime if i let off the gas for a few seconds car will smooth out and return to normal operating performance. i dont know where to look now. i dont want to replace the injectors, computer, o2 sensor, ect. what should i do next? i want this problem fixed and i dont want to pay someone to fix it. i also thought i should metion that the car acted up so bad once that it literally (backfired) "blew up the mufler". its now balloned, looks like a sealed tin can that someone put a bomb in it.

 

i am by no means an expert but, but ill take a crack at this because it sounds similar to what has happaned to me. you said you replaced the cap? are you sure that the wire placement is correct? i once crossed some wires and had the same problem, also if the caps terminals got wet at any point they could be corroded and giving the worst hessitation/backfiring issue youve ever seen. Again something that has also happened to me in the past! i hope this helps if not hopefully someone chimes in with another idea

 

sorry what you said doesnt help, if that were true car would run terrible all of the time. it runs terrible some of the time.

 

When does it run terribly? Are there any particular conditions that bring it on?

 

have you changed the ignition module?

 

Not necessarily true. It's sometimes amazing what will run and what won't run, and how.

It really sounds like an ignition problem - no one is implying stupidity, but we all know that we've made the silliest mistakes ourselves.

The best bet is to start at the beginning, as mundane as it seems. Get TDC on #1 cylinder. Check firing order. Recheck firing order. Check plugs, wires, make sure wires are fully plugged to plugs and cap, make sure all wires have continuity. Check timing (unplug EST). Check distributor, rotor, cap. Have ICM tested. Check all vacuum lines for cracks, and check for vacuum leaks with spray carb cleaner (not starting fluid - too volatile!).

The weirdest problems are usually the simplest things, just overlooked. And I have plenty of room to talk, I usually overlook all of them!

 

There are numerous things that could be causing your problem. I would suspect a fuel problem and or a bad O2. Both of these items could cause your car to run normal one minute and then terrible the next. A new O2 is a good idea, costs $20, and takes minutes to replace. It is a good idea to replace anyways if it has not been changed. A bad O2 will not always throw a code either. I have had two O2's go bad on two different TBI vehicles and neither one threw a code. If this does not cure your problem I would rent a fuel pressure tester and verify that you have at least 10psi feed line pressure. If not, your pump is heading south and not coming back.

In addition to these common issues two less likely culprits would be a failing MAP and or CTS sensor.