LT1Jeepin

Hey guys, I recently did a tune up on the LT1. New plugs, wires, cap and rotor. Also replaced the power steering pump while I was in there and cleaned up the motor. Also replaced the exhaust manifold gaskets too. None of which should cause a high idle. It's idling at about 1300 rpm. I do know that my MAF is not working correctly, so for the time being it's unplugged. When I plug it in it cranks the idle up a little higher. New MAF is on the way. I checked the plug to that just to make sure it was getting a 12 volt, ground and a 5 volt signal. It's all good. Again, it's unplugged. I will say that when it cranked the engine started to idle high with the MAF plugged in and the MIL came on. So I'm not sure if that code was from the MAF or not. So with that being said, it's running like it has a vacuum leak somewhere and it's getting pirate air into the system. I don't believe thats the case but thats what it's acting like. Any suggestions? I know I haven't had the code read yet, but just looking for suggestions. I know the battery was disconnected for a while and the computer has to "relearn". Would this have anything to do with it? Any help would be appreciated.

LT1Jeepin

Have I stumped everyone? Glad I'm not the only one that doesn't have any ideas. Please keep thinking about it, and as soon as I can get it scanned I'll post up the trouble codes.

mrmint69

Really need to install the new maf and see how it acts. Plus read the codes after resetting. Hard to say with parts not working or hooked up correctly and if that would fix it.

mrmint69

BTW, How did you "clean up the engine"?

Injuneer

Is it possible you have a loose harness connection to the coolant temp sensor in the water pump? Low coolant temp tells the PCM to raise the engine idle speed, and to richen the A/F ratio. Check it again for codes.

LT1Jeepin

by cleaning up the engine, I simply wiped it all down. It was a little bit of a greasy mess. I didn't soak it with water or anything like that. Just simply sprayed some degreaser on a rag and started wiping.

Other than that I'll check the CTS but I am pretty sure it's working though. It's worth looking at though. I just thought it to be odd that after having a tune up that it's running faster. But I'll double, double check it. Thanks guys.

mrmint69

I would recheck all your work and make sure everything got hooked back up correctly.

LT1Jeepin

SOrry it's taken so long to get back on here, but here's what I found. On the way to get the engine scanned, the motor started to run horrible, like it was only on a few cylinders. Managed to get it to the garage. The left bank O2 sensor was giving a DTC the reading was stuck on 454 and wasnt moving. Also there was a High Pulse Resolution DTC and there was the Mass Air Flow DTC. Now the vehicle is idling in upwards of 2,000 rpms. Everything is in it's proper place and nothing is broken that I can see. We cleared the codes and cranked it again to see if they showed back up and the only thing that was there was a DTC for the MAF. I don't understand that. Do you guys think the PCM is on it's way out?

Also forgot to mention that another MAF is on the vehicle too where as the old one wasn't working (I think). If you unplug it with it running it makes no change in the idle problem at all. Like the PCM isn't reading it possibly?

RamAir95TA

It is very unlikely it's the PCM. Most auto shops who lack the proper knowledge, equipment, and expertise are ALWAYS quick to blame the PCM when in reality it is RARELY the problem. Having been in this game for 13 years I have seen ONE instance where a PCM went bad.

Have you tried looking for an intake leak? A leak can cause a higher idle. Look around the throttle body elbow for tears/holes.

mrmint69

Check the O2 sensor that wasn't moving for damage and replace if you see nothing thats an easy fix. Get ac delco if possible.

WhiteKnight2001

Vacuum leak maybe?

LT1Jeepin

Ok still chasing a problem with the idle. New O2 sensor for the one that wasn't working. Still a high idle. No codes have shown up since I put it in. I can pull the hose off the brake booster to "create" a vacuum leak and the idle actually slows down. Plug it back in and the engine speeds back up to 2k rpms. I sprayed the intake and the hoses with starting fluid while it ran to try and find a vacuum leak but come up with nothing. Am I wrong to think that its telling it to "feed" the fuel seeing as when I pulled the booster hose it slowed down? Any more ideas guys.

OBE1 95Z28

Did you recently clean the throttle body? I found that my idle would be high after cleaning the TB. Dab some oil on the pivot points of the butterfly rod where they enter the housing..cured my high idle.

LT1Jeepin

Yes I checked to make sure that the throttle plate are closing off all the way. Thanks for the suggestion though. Well now the problem is back to where I can pull the booster hose and it will speed up. Check engine light has came back on. Also, I had a hard time trying to start it after I cut it off. It would crank then immediately die. Then it done it again, then it cranked up and ran fine. I think it sounds like a vacuum leak but I can't find it to save my life. Any possibility it could be a throttle position sensor? I don't know if that would throw a code if it was still working though. Just throwing ideas out there from my thought process but I could be way off.

mrmint69

Check it for codes and install the new O2 when it arrives. Those are really your only next steps at this point.