1993 Z28 LT1 rough idle problem - Camaro Forums

mtm · #1 02-28-2007, 01:01 PM

What's up guys, I'm new to the site. I just bought a really nice 93' Z28 LT1 automatic camaro for a great price. The only problem I'm having is it has a little flutter during idle. Sometimes enough so that when I put it in gear the car dies. It has new platinum plugs, MSD 8.5mm wires, distributor, air filter, and J.E.T. chip. The guy I bought it from had everything done which was pretty costy on his part. After getting fed up with the flutter he sold it to me for cheap. Anyway, I'm not sure what it could be. It's only doing it during idle. After about 2,000 RPM you don't even notice it. Normal driving is perfect and the car runs awesome. Its just during idle. I think it has something to do with a vacuum line. From what I've heard, when a motor is at higher RPM there is no vacuum so the car wouldnt be effected which is exactly how its acting. My dad thinks it might be out of time but would that make the car run rough the whole time not just during startup and idle? Has anyone heard or seen this problem before? Thanks for any help or suggestions.

z28pete · #2 02-28-2007, 05:15 PM

Make sure the EGR is working properly and not sticking open, check the Idle Control valve & make sure the throttle valve blades aren't sticking, and that Throttle Position Sensor is working and adjusted properly. Also you may want to remove the Jet chip and repalce the MEMCAL chip with the latest vesion from GM.

toml14 · #3 02-28-2007, 05:45 PM

My 93 Z does the same thing. No check engine light but I did hook it up to a scanner and everything seems to be operating smoothly. Mine really only does it after about 15 minutes of idling. I have never had it shut off either. maybe it has something to do with the JET chip which I have also. Z28pete may be on to something here. Im going to leave mine alone for right now as it doesn't bother me that much. Good luck with that though hope you figure it out.

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mtm · #4 03-06-2007, 09:12 PM

Well I had a buddy try to hook up his scanner to it and for some reason it wouldnt read the cars ECU. So we replaced the JET chip with the stock chip that came in the car and still no luck. Its running the same way. I took it to a local dealer and they hooked it to their diagnostics machine and he said it was the distributor. He told me that the water pump leaked into the distributor and ruined it and that it would cost me $1026.00 to fix. Now I understand that this is a common problem, but the car just had a new water pump and distributor at 114,000 miles. It currently has 116,000 miles. I would think that if the distributor was screwed up than the car would be running rough regardless of the RPM. After about 2,000 the car is fine. I am not trying to say the guy that scanned it is not good at what he does it just doesnt seem to be that big of a problem to me. I could be wrong but I hope that I'm not. Here is a quick video I made of the tach with the car running. Keep in mind that I am not messing with or giving it gas at any time during the video except for the first big Rev. Watch how much the RPM's change during idle. If anyone has any suggestions please let me know. I really don't want to pay someone $1,000 to fix something that may not be the problem.

VIDEO: http://s4.photobucket.com/albums/y14...MPEG0001-1.flv

camarorz28 · #5 03-07-2007, 01:07 AM

has the car shut off when its at idle?like when you are at a stop light, does it still idle like that? will it shut off?

95slvrZ28 · #6 03-07-2007, 02:47 AM

Did you do what Pete said and check your EGR valve? Pull if off the back of the motor and see if there's a lot of build up on it. If there is, clean it(maybe use some carb cleaner the help you get all the carbon off). Put it back on, if the problem persists, order a new one.

mtm · #7 03-07-2007, 04:11 AM

Yes the car has shut off at idle. If i leave it running in park, sometimes it will just spit and sputter and pull the engine down low enough to kill it. At stop lights and signs I usually have to hold the brake and give it a little gas to keep it from missing.

sellc · #8 03-07-2007, 04:19 AM

After checking all of the above, I sometimes see when people add aftermarket parts the base idle needs to be adjusted to compensate for the increased air flow. What is your car idling at in park? What does it drop down to with your foot on the brake in gear?

mtm · #9 03-07-2007, 04:36 AM

Quote:

ORIGINAL: sellc

After checking all of the above, I sometimes see when people add aftermarket parts the base idle needs to be adjusted to compensate for the increased air flow. What is your car idling at in park? What does it drop down to with your foot on the brake in gear?

At idle, the car is acting the way you see in the video i posted a link to. When i drop it in gear it drops down to about 500 RPM. How do you adjust the base idle? You have to do that with the computer right?

sellc · #10 03-07-2007, 06:16 AM

I didnt see the video at first. Seems photo bucket is down for maintanance.

500 sounds low. Adjust the base idle by way of the throttle stop screw right there on the t-body. Take it easy and dont get carried away. 1/4 turn at a time, goose it and see where she falls. Turn to the right to increase and turn to the left to decrease.