94 3.4l problems

[bryanjck]

My 3.4l Camaro started having problems with the idling. It would idle anywhere between 1500-2400 sometimes. I replaced the Idle Air control valve thinking it was the problem. Here is where it gets weird. It fixed my problem for about three weeks then started idling high again. I figured the IAC valve could have been a dudd so i took it back and got a new one. THis time it didn't fix it. THEN I started to get a check engine light every once in awhile. When i got the light then my tranny wouldn't shift down into 4th gear and my cruise control stops working. This only happens sometimes. Usually when i've been driving for awhile like on a trip. My idling problem is usually there but on a lucky day the car seems to idle fine. Could this be a PCM problem? Please let me know what you guys think.

[blindeyed]

You could possibly have bad ignition coils. Things like that start to go out on vehicles 10+ years old. I'd try replacing those. Sounds like an ignition problem. Also, have you changed the plugs and wires recently?

[bryanjck]

Thanks, Ill try replacing the coils. My plugs and wires were replaced in January or so so they should be good right

[Matt365]

unless cheap wires were installed and the silicon melted from the high heat, or someone installed them incorrectly and laid them across an incredibly hot part of the engine.

[CamarosRsweet94]

I don't see how bad ignition coils could cause a car to run high RPMS when idling. If one goes bad the car will probably miss badly or not run at all, and the likelyhood of all three of the coils going bad at once is pretty low. The coils also would not explain the transmission shifting problem...

[blindeyed]

Originally Posted by CamarosRsweet94

I don't see how bad ignition coils could cause a car to run high RPMS when idling. If one goes bad the car will probably miss badly or not run at all, and the likelyhood of all three of the coils going bad at once is pretty low. The coils also would not explain the transmission shifting problem...

Well I'm just giving him my best guess as to what the problem may be. It does sound like it might be an ignition problem, but I'm not too familiar with his type of situation. And since he said he already replaced the IAC (which was my first guess), then that was the only other thing I could really think of. But you do make a point, I wouldn't see bad coils making the rpm's higher either. I guess I overlooked that part. As for the tranny, I just assumed that whatever is making it idle at high rpm's is setting off the SES light which in turn is somehow affecting the transmission shifting gears. Same with the cruise control, since he said those both are being affected only when the light came on.

The only other things I could think of would be (1 being from the most likey):
1) Bad Intake Air Temperature sensor
2) Fuel injectors may be clogged.
3) Fuel filter may be need to be replaced
4) Leaking EGR valve or plugged PCV valve
5) Vaccum leaks (intake manifold or plenum)
6) Leaking head gasket
7) Bad 24X crank sensor. (see explanation below)

Your IAC valve may have not been the problem. On the 3.4's, there are 24X crank sensors which filter the MAP (Manifold Absolute Pressure) signal at speeds below 3000 RPM. The ECM then reads MAP output at each of the 24x reference input signals. The ECM then averages MAP reading for fuel control. So the IAC valve posistion is not needed to caluclate air flow at idle for fuel delivery. So, speed density fueling is being used at idle, in addition to higher engine speeds. Summed up: Based on how fast your crank is turning under 3K RPM's, the 24X crank sensor will send that signal to the ECM which then provides you with the sufficient amount of fuel to run properly. This would really be the last thing I would assume that could be wrong. But there's always a chance that this sensor could have gone bad.

I would try taking the car to Advance Discount or Autozone to run it for codes and see what/if any come up before trying to diagnose the problem any further.

[jackmalone2001]

What about the oxygen sensor, try changing those! But before changing anything take your car to Autozone to have them run codes! IT'S FREE!

[ASE jish]

Im a mechanic myself, and also have the same problem with my 3.4l camaro.

In my situation the rpms @ idle average 1500-2500 rpms, and the service engine soon light (MIL), comes on and goes off. When i gear the car drops back to regular rpms (800-1000).

Proper diognostic procedure

1. check for broken wires and poor grounds to and from PCM (computer)
(located left top fender of engine compartment). Also check fuses and relays both under hood and in dash.
2. check for broken/split/damaged vacuum lines
3. check the altenator for correct current output, and also check for amp ripples ( bad diodes in the alt. cause amp ripples wich can make the PCM and other electric controls act possesed)
4. scan for present DTC codes
4A. if codes are present identify codes and follow same ground and electrical checks for related sensors, if npf replace sensor and clear codes.
4B. if (MIL) is on but shows no present codes, unplug TP sensor and run engine at idle for 10-15 minutes. Rescan for codes, if a Throttle position sensor code is present PCM is functioning properly. If no code is present the PCM is not functioning properly and needs to be replaced.

5. If all above are operating correctly, make sure there isnt excessive fuel addatives in your gas (fuel treatments, octane boosters)
Too much fuel addative can overwhelm your PCM when attempting to adjust for fuel air ratio (fuel curve).
This can also cause evap system DTC codes to become present.
Remember 3.4l's are programmed to run on regular unleaded not rocket fuel. : )

6. Once diognosed and repair costs are estimated, ask yourself why you havent swapped to a 350 or better yet a spanking new 502 crate engine.
3.4l engines are pleagued with problems and often arent worth the time once over 100k.

[blindeyed]

Originally Posted by jackmalone2001

But before changing anything take your car to Autozone to have them run codes! IT'S FREE!

He wouldn't be able to. He has a 94 with OBD1. If he had a 95, as I do, then he would have OBD1 with the OBD2 style connector. Last time I went to Autozone, I had a guy trying to tell me that he couldn't run my car for codes because it was a 95 with OBD1. But I had to correct him and let him know that I had the OBD2 connector under my dash. He didn't think it would work, but it did. Came out telling me that a solonoid in my egr wasn't functioning correctly.

Originally Posted by ASE jish

Once diognosed and repair costs are estimated, ask yourself why you havent swapped to a 350 or better yet a spanking new 502 crate engine.
3.4l engines are pleagued with problems and often arent worth the time once over 100k.

I tend to disagree with your last statement. My friends 2000 Trans Am has had more problems with it in the past month than mine has had in over a year. The only thing wrong with my car right now is my transmission mounts, and shocks are going bad. Not to mention my engines got 102K miles on it and still runs as good as the day it came out of the factory, if not better. I love my car and my engine, despite the constant putdowns from people like you.

[jmwakd]

I also have a 95 3.4L and it has 311,000 miles on mine and other than the usual stuff that has to be done to all cars I just had to change the egr on mine. It still runs good.

[ASE jish]

scanning a 95 camaro with obd1 with obdII connnector is not a problem, you just need the right equipment. No the autozone 90 dollar scanner will not work. for the right kind of diognostic tools look at snap on scanners. they have scanners that can do tech1 techII obdI and obdII, and also give you alot more than just a code. you can scan data streams wich show you things that may be functioning improperly but arent pulling codes (MIL) lights. they also have troubleshooting tips for different tests and procedures to help you from making an incorrect diagnosis. Granted they scanners are very .... very ... very ... expensive. 2,000-10,000 dollars. ; ) got four of them myself, and they have made me my money back and double. They more than pay for themselves if your thinking of becoming a mechanic professionally.

[BiH]

dude if your think a 350 motor is any better then a 3.4 your out of your mind.my friend had a 96 T/A and that thing was always in a repair shop,while my 3.4 ran like a champ

[1stmaro]

I have a 95 3.4 Camaro that has the same problem as bryanjck's car. I know this is an old issue but just wondering if anything was figured out on this issue. I have a solus pro scanner but these cars don't allow for many test to be done with a scanner and I haven't put a lot of time into figuring it out because this problem may happen once a month and when it does I can take a screw driver handle and tap on the ECM and the problem goes away but I don't want to replace the ECM if that's not the real cause.

[gmtech1]

Sounds like you found the problem.