Hey guys, I'm new to the forum (and DIY car repair, to an extent.) I am excited to contribute and learn here. I know these old 3800s are strong engines, and can be a good option to "learn" on.

My question is in regards to my girlfriend'* 95 Buick Regal Custom.
Car:
- 3.8
- V6
- L27 Series 1

Symptoms:

- Originally, the car was experiencing stalling issues. These almost always occur at low speeds, and often when turning and not accelerating.

- More recently, the car has begun an extremely high idle. After ignition, the idle will sit just about 2000 RPM and slowly increase. This high idle is most severe in Park and Neutral. When shifted into drive, the problem abates somewhat. However, shifting from Park to Reverse is very jarring.

- Coolant leaks have always been a problem in her car. In the last year I've paid to replace the thermostat and the water pump. As neither fix ever lasted very long, I'm starting to think my mechanic either misdiagnosed the issue or was "playing the long game." Note: The coolant leak is most noticeable on the back of the engine and on the driver side below the throttle body.

- I recently have noticed brown oil spotting in the coolant overflow tank.

- The oil itself seems normal, with no evidence of a "milky white" appearance.

What I've done so far:
1. Cleaned IAC valve - no positive results.
2. Cleaned MAF Sensor & Screen - Possibly good results. The "High Idle" seemed to now be around ~1600 RPMs. However, this was done a day after I last started & had the 2000 RPM issue.
3. Cleaned all electrical connections - no positive results.


My Thoughts on possible issues:
1. Intake Manifold needs to be replaced - Is this common on the Series 1, or only on the Series 2?
2. Blown Head Gasket - Again, isn't this more common on the Series 2?
3. Possible vacuum leak? I know this wouldn't explain the coolant, but the high idle issue is by far the newest development - making me think there may be two separate issues now.
4. PCM? - A gentleman on youtube made https://www.youtube.com/watch?v=j6TkhLyh0_A which shows a very similar issue. His ultimate fix, detailed in the video'* comments, was the PCM.
5. Heater hose - Through my research on this site, I found this post by a guy suggesting that it may not be the UIM.



Regardless, I am very thankful for any help you guys can offer me! I have no father or anyone to ask these questions - so i'm thankful for the internet!

Note: Under Possible Issues, I accidentally formatted the hyperlink incorrectly. You can find the Youtube video I am referring to here.

Sounds like an intake manifold gasket issue to me.

Unfortunately I figured as much. I've got myself half way there, and unfortunately it'* a little too cold today for me to get out there. Do you have any suggested videos/ instructions for this job? Is there anything I could gravely **** up? I'm good at following detailed instructions, but I'd hate to get into a scenario where I do one small thing wrong and the consequences are a completely ruined car. As I said, I've done minor repairs to cars (alternators, belts, circuit boards, flashers, turn signal switches etc...) but never anything as detailed/ requiring as much be removed.

As a side note, is there anything I should go ahead and replace/ check while I'm this far into it? I'd rather confront future issues proactively, instead of pulling all this again when the next common issue arises.


One more question: with so much of the engine pulled, am I at danger of morning frost/condensation ******* up the engine? I.e. with the EGR tube pulled, and many vacuum tubes pulled, do I need to worry about letting the car sit a day or two? It'* just too cold here to get in there right away. The car IS covered by an open carport, and therefore cannot be directly snowed or rained on.

​​​​​​​Thank you so much for any advice or help you can give!

Here are some thoughts specific to the L27.

I have replaced the UIM on my '93 Park Avenue. This happened a few years ago, back when the car had 170k miles. My '94 Regal likely needs to have it done, as it is starting to show symptoms that I noticed on the Park Avenue.

This is my original thread on the ordeal: https://www.gmforum.com/buick-172/l2...cement-303150/

I never had idle issues, only coolant leaking from between the UIM and LIM on the throttle body side. The coolant temperature sender is under where this would leak, so if it does take offense to being leaked on, it could cause the symptoms you are describing, but it would also show up on a live data scan, and probably set a code. The thermostat housing could also put coolant back in the area you describe as well. There is also a plate over a coolant passage that can leak in that area as well, but I have yet to even find what the plate is, much less a case of one leaking. Finally, you could also have a throttle body gasket leak dumping coolant, which could be causing a vacuum leak, but that would usually make the car run bad instead of revving high.

Just about anything will show up on a live data scan fairly quickly. Have you tried pulling codes or scanning live data?

And the only concern would be dirt in the lifter valley, or dropping something down an intake port. Any condensation shouldn't be too much of a concern, especially because you should change the oil afterwards anyway.