Part time miss?

[Dotyereye]

I have been reading here for a few weeks and have not found anything exactly like the problem I'm having.

I have a 94 3.4L camaro. The miss started after I put some fuel injection cleaner in it, but I'm not sure it has anything to do with it. When it first started I could shut the engine off for a few seconds and restart it and it would clear up Then it seemed to happen more offen and shutting the engine off and restarting would not always fix it. Now it is to the point that when I first start it {cold start} it runs fine but after I get down the road some it will start to miss. It also will do it any time I stomp it hard, and does not go away until shut it down and let it cool down some.

The miss reminds me of when you foul out a plug or two or burn a wire or two in half. Because of this I am thinking it might be a coil breaking down but am not sure. I'm taking it to run the codes tomarrow. The cat has been removed and the guy I bought the car off of did not put the o2 senser back on behind the cat but has run fine for 3 months until the last 2 weeks. It has duel exhaust and a cold air intake. Any thoughts?

[Turbo V6 Camaro]

check plugs and wires first
then coils
then you ICM

the scan should tell you what cylender # is missing though

[Dotyereye]

What is ICM?
I ran the codes @ auto zone today and came up with a bunch. They all seem to be low or high voltage to about everything you can think of. It also told me I had a problem with my ECM. This is the computer right? Would the ECM be the why the voltage is messed up? They also told me to change the Map senser. What do you guys think?

[i_love_my_maro]

i woudl think that it is your coil or you ICM

[SirShaun]

I wasted 80 bucks on a new coil pack, new sets of wires and everything. The SES light never came on or anything. I have 1 cylinder still completely down. My dad and his friends believe an injector went bad. This weekend new injector gets put in hopefully my cam will run on all 6 once again. Also my car is a 94 camaro too with 115k on it. If your mileage is similiar to mine might want to test injectors.

[BLLDOGG]

dont think of it as a waist, now you dont have to worry about you coil pack or wires for a good amount of time and you are narrowing it down [img]smile.gif[/img] think positive ;)

[Dotyereye]

Originally posted by Dotyereye:
What is ICM?
I ran the codes @ auto zone today and came up with a bunch. They all seem to be low or high voltage to about everything you can think of. It also told me I had a problem with my ECM. This is the computer right? Would the ECM be the why the voltage is messed up? They also told me to change the Map senser. What do you guys think?

Some of the codes I got.
Left ox senser er bank 2.
Coolant temp senser signal volt high on open.
Low or short circut.
System volt too low.
Throt pos senser sig volt to high.
Map sen sig too high.
Map sen sig volt too high.
Too low volt map senser.
Ign system loss of 24x sen sig.

This is just some of the codes I got. I think there was 41 all together. Can some of these be from older codes that did not get deleted? Or can the computer cause all these problems?

[Dotyereye]

? :(

[Fredless]

reset the ECM and drive the car for a day, then get it re-scanned. Possible old codes.

[Dotyereye]

How do you reset the ECM?
Disconnect the batt?

[pontiac nino]

You don't have a o2 sensor on the cat just two, one on each manifold. The miss may be a bad o2 (Im leaning more towards that just mho) since it occurs only after the car has been warmed up, but, it can also be a bad spark plug wire or maybe even a ignition coil.
Yes disconnect the battery for 10-15 minutes drive it around for a little bit, see what happens, if the same code reappear.
Couple of questions.....

Where did you put the fuel injection cleaner through? gas tank or pcv system?
By miss do you mean it backfires? surge? rough idle at park?

Niño

[Dotyereye]

I put the fuel injection cleaner in the gas tank.
The miss is like you diconect one or two plug wires. Real choppy. Its the same @ park as going down the road. Sometimes I can shut it off, wait a few, and start it back up and it will run fine.

[pontiac nino]

O2's or a ignition coil, jmho.

[Die Ford V8]

i'd say start with two new o2 sensors and start fresh. their not that expensive.

what i am thinking is that when your car is cold it is in a Closed or open "loop mode" which means your can starts up and runs off the what the computer tells it to (no sensors) till it warms up. when it warms up the sensors can accuratly read. your temp sensor will trigger the other loop mode and your car will start running off sensors.

if your sensors are bad, your engine will run bad since it is making judgements from bad sensors.

the reason your car runs ok when it is cold is because it is not making judgements from bad sensors, but from good readings previously stored in the computer by the Manufacturer.

its hard to put into words so if anyone can add or edit my paragraphs go for it.

also check to see that your wires arent close to the exhaust manifold. the hotter they get the worse they conduct electricity.


also list the codes and their numbers fully in order.

if you can sweet talk a mechanic into resetting your "current codes" then drive around for a day. (if the disconnecting battery thing doesnt work)


also when you list the codes list the "current codes" and the "previously stored" codes seperately


good luck and i hope this helps

[Dotyereye]

I finally found the problem! It turned out being a short in the fuel injection wiring harness on the number 3 injecter. As soon as the PCU would read the short it would kill that injecter until the computer was reset. [img]graemlins/rock.gif[/img]