Madix

Vehicle: 2001 Chevy Lumina (3.1 L)
Problem/Symptoms: very poor idle/high pitched whine

Hey there! This problem has been the bane of my existence for the past month and I’d greatly appreciate any input.
The problem started when I had a badly leaking intake manifold gasket about a month ago (I knew it was the gasket because of where it was leaking from). I tried several mechanics but none in my area wanted big jobs. -I did get 1 guy that said he’d look at it but for some reason he just wanted to string me along rather than just telling me he can’t do it. I understand that I could take it to the dealership but they'd likely charge more than the car is worth.

Lacking other options, I decided to do the job myself (I’ve done smaller jobs before and all went well). I was able to take everything off, replace the gasket, and put everything back together, no extra bolts or anything. I actually did fix the coolant leak but now the engine is running very rough. It has an unsteady high idle (2000 rpm) and is making a high pitched noise that’s constant and especially bad in higher RPMs. Lights and power dim as the idle fluctuates. The sound is very prominent, sounds almost like a belt squealing that increases with RPM. I don’t have fancy equipment but I do have a basic scanner- the codes are P101 (mass airflow sensor) and P300 (random misfires). I suspect there may be a an alternator issue or a vacuum leak somewhere but everywhere I look I’m noticing other problems- I noticed my spark plug wires were damaged, some sensor wiring was damaged, and some vacuum lines were damaged. I went through and replaced everything I noticed (I had no idea taking everything apart would cause so much damage) but I suspect there may be other issues. I'm leaning towards a vacuum leak as the P101 code is unrelated to alternator, right?

Other things to note: Car was running perfect before I took intake off, no codes. Car starts up fine but sometimes stalls in idle. When tightening intake AND plenum bolts I could hear "popping" noises on many of the bolts before even getting close to appropriate torque (used a new 10-80lb torque wrench). Something else to note was that the old drive belt got some power steering leakage on it during the job, I cleaned it the best I could but when taking it off I had to peel it off the pulleys, some of the rubber was still stuck on the pulley. I ended up replacing it after I noticed this but I suppose it may have caused damage to some bearings.

I'm thinking I may have to do the entire job again or buy another car

Thanks!

kevinkpk

Sounds like vacuum leak also. I'd suggest replace vacuum lines

Madix

Thanks for the reply!

I just sprayed carb cleaner around in hopes of finding the leak. Seems like I get the most response by spraying near the middle/back fuel injector but It's hard to tell for sure since the plenum is blocking vision and the whistle is so high pitched that it's hard to hear anything change. I can't think of anything else near there that would cause a leak besides the plenum gasket (which is brand new). -The old plenum gasket was actually very difficult to remove, it was basically welded to the surfaces and required a lot of cleaning with a razor blade.

I bought an injector o-ring kit on amazon and will try replacing them next week. It makes sense for the injectors to leak now that I think of it- I did loosen the fuel injector rail bolts and lifted them to fit my socket in to remove the intake bolts so it's possible the o-rings may have broken their seal, especially considering that the o-rings are 20+ years old and probably dry-rotted.

Madix

Update:

Found the leak- it was the upper intake manifold that was cracked. The crack was very hard to see and I didn't notice it til the 3rd time I had it off.I knew it was in that area based on the sound from the carb cleaner, honestly thought it was the fuel injector that was directly below it though. -I think it cracked because that bolt wasn't tightened enough compared to the other 5 bolts- causing that section to be higher than the rest of the intake bolts.

I was just going to seal the crack with RTV but I managed to find a used intake manifold for only $40 on ebay.

90zEraWhips

I'm experiencing this same issue it's leaking air. Is it just the upper manifold gasket that needs to be replaced ? What cost am I looking at parts + labor time?

mountainmanjoe

@90zEraWhips
use a smoke machine to find the exact location of the leak