***** 1995 Pontiac Bonneville 3800 II help needed *****

[MeLLoCeLLo]

I'm sure this has been brought up before many times. I'm just not sure if I've done everything I could do.

I just recently replaced LIM and UIM gaskets. I took my time and made sure everything was done right (or so I thought). Now my car idle's rough. At cold start it's at its worse, then while warmed up, smooths out. I've researched and done the following:

-pcv change including o-ring
-cleaned mass airflow sensor
-replaced idle air control valve (very rusty and seal was bad)
-checked plugs, wires, coils

Check Engine light goes on and off (mostly on) and did a test. Don't remember the codes but said running lean and brings up the "MAF code", also brings up the "o2 sensor front" code.

I replaced the o2 sensor last year. It may have messed up with the coolant leak.

The car runs great with normal driving, just at stops and really low speed (parking/traffic) is when it acts up. I doesn't shut off but it really bothers me.

Is there any help that could solve this issue? Is there something I may have missed or over looked? Thanks for your help!

[myfirstbonnie]

Did you have coolant getting burnt through the engine? Did you clean the TB bore where the IAC goes in? Clean the TB and MAF using the correct cleaners. Check everything over and make sure there are no vacuum leaks. Check by spraying carb cleaner around the fittings and see if the idle changes. Check around the base of the LIM and UIM to make sure they are sealed.

Have the codes read again and report them back here also.

[willwren]

It's not uncommon for coolant to kill an O2, especially an off-brand. Never use Bosch.

Follow Matt's advice above first though. Basic maintenance and checks, then get codes.

[MeLLoCeLLo]

I did have the infamous internal coolant leak. I drove it with this problem for awhile until I researched it on the net and found out how common this problem was. When I opened her up, I just couldn't believe the pool of coolant sitting on the LIM. UIM was covered with thick coolant deposits also. So I know it ingested a serious amount of coolant. Yet still, I never had rough idle issue.

I did clean the TB and other sensor openings surrounding it. I used throttle body cleaner for TB and MAF cleaner for sensor.

As for checking for vacuum leaks, I did spray a decent amount of throttle cleaner around UIM and did not notice any idle changes. Do you think I could have under torqued the UIM? I torqued the LIM pretty well (since it was aluminum with aluminum gasket). UIM was torqued at a scary 15-20 LBS (obvious UIM/gasket plastic's). Should it be torqued more? I've been driving it for a week and I have no more coolant/hydrolock issues.

Can I clean an o2 sensor? Should I tighten UIM more? I also have heard people change the fuel pressure regulator; is there a way I could test to see if it's bad? (fuel rail was resting upside down for two weeks till I had the time and parts to work on car)

I appreciate the expertise anyone has on the matter - Will try and get codes again soon.

[94SilverSSEi]

If you are talking about torquing the bolts from the UIM to the engine I believe you overtorqued them as it says 89in/lbs is the recommended torquww in the tech info

Also my car had a similar issue and it had a very rough idle at first after doing the work and I couldnt figure out what it was so I just left it alone and after a couple weeks it seemed to fix itself. Although my engine was actually entirely filled with collant and burned a lot of it...(thats another story) but anyways I believe after all the collant was burned out it kind of fixed itself and also I was having these 0-2 sensor codes and after a couple days they went away on their own. So personally I would say leave it for a week or so and if it doesnt get better at all then I would start replacing stuff.

I know all cases are different but this is just my 2 cents

[willwren]

Torque specifications are in Techinfo. You cannot clean the O2. How old is it? Are you losing coolant or is it staying stable?

[MeLLoCeLLo]

If you are talking about torquing the bolts from the UIM to the engine I believe you overtorqued them as it says 89in/lbs is the recommended torquww in the tech info

Also my car had a similar issue and it had a very rough idle at first after doing the work and I couldnt figure out what it was so I just left it alone and after a couple weeks it seemed to fix itself. Although my engine was actually entirely filled with collant and burned a lot of it...(thats another story) but anyways I believe after all the collant was burned out it kind of fixed itself and also I was having these 0-2 sensor codes and after a couple days they went away on their own. So personally I would say leave it for a week or so and if it doesnt get better at all then I would start replacing stuff.

I know all cases are different but this is just my 2 cents

Okay, I think I may have under torqued; Meant to say in/lbs. I noticed when engine is hot that I could tighten a little more, so I might try tightening it this weekend. Might take your advice and leave it only. Im going to drive it on the highway for a bit today.

[MeLLoCeLLo]

Torque specifications are in Techinfo. You cannot clean the O2. How old is it? Are you losing coolant or is it staying stable?

Like I said before, Coolant issue is fixed; Just the idle is rough. O2 sensor is about a year old.

[94SilverSSEi]

Also I forgot to mention it is crucial that you keep checking your coolant level and make sure it is not going down as this could be a problem.
I have also heard that seafoam can work good but sometimes it takes out your 02's or whatever so be prepared to do a tune up if u use seafoam

[MeLLoCeLLo]

Thanks to everyone, I may have found the problem. Looks like I didn't spray under UIM under the throttle body. Seemed to rev a little after I sprayed a good amount when engine was warm.

I tried to tighten more but didn't seem to help. I had borrowed a torque wrench and did not have it with me, so I'm a little weary of tightening it more without it.

I guess I'll try and tighten more on the weekend; or would it be a good idea to pop it out and see if it settled in right?

Any other advice would be much appreciated.

[myfirstbonnie]

Did you replace the UIM or just the gaskets?

[MeLLoCeLLo]

Did you replace the UIM or just the gaskets?

Both. I bought the GM "sure fix" gasket kit:

http://www.ineedparts.com/index.php?tar ... t_id=17806

[myfirstbonnie]

You want to make sure you don't over torque it. It will break. Didi you torque them in the proper pattern? All surfaces were cleaned and smooth before install?

[MeLLoCeLLo]

Yeah, I don't want to break it. Surface was clean and smooth. It went in fine, maybe just not tight enough or not perfectly lined up. I feel I should take the UIM out again and try lining in up. Is it wise to do so? Should I use a little RTV gasket maker?

[myfirstbonnie]

No, shouldn't need any. Try spraying a little more and see if you can locate exactly where it is causing the idle to change.

[MeLLoCeLLo]

No, shouldn't need any. Try spraying a little more and see if you can locate exactly where it is causing the idle to change.

I sprayed the UIM under the TB, near lower right hand side of TB - looking towards engine - standing on driver side. When I tightened the UIM, it seemed quieter (faint hissing I missed before and thought might have been normal). I've never really had the Engine cover off before with engine running, so hissing didn't catch my attention.

[MeLLoCeLLo]

So... Would it be ok taking out the UIM again to line it up with the LIM?

Doesn't seem like it lined up right. I tightened it enough (don't want to tighten any more).

Seems vacuum leak doesn't want to go away. I was also thinking of spreading rtv where the leak is and letting it dry.

Whats your take?

[bill buttermore]

As others have pointed out, your symptoms are those of a vacuum leak. One of the bolts for the UIM on the right of the throttle body is actually a stud, IIRC, that requires a larger socket than all the other bolts. I think maybe the bracket for the EGR is attached to it. You will need to remove anything on the stud to properly torque it. 20 in-lb of torque is definitely not enough to seal the UIM. 20 ft-lb is way too much - in fact, the little 6-mm bolts will probably break before they get to 20 ft-lb. The proper torque is 89 in-lb. That's 7-1/2 ft-lb that is pretty easy to get accurately with a 3/8"-drive beam style Craftsman torque wrench that sells for about $25. With a new UIM gasket and a new UIM, you should not need any RTV silicone. Did you follow the instructions in the Techinfo article for changing out the UIM? Sometimes the runners inside the UIM need to be wiggled into place to allow for a good fit of the UIM gasket against the LIM. It will probably be worth your time to pull the UIM and try again. You should not need a new gasket. Buy, borrow, or rent a small torque wrench and buy some blue threadlocker for the UIM bolts. They tend to get loose over time if you don't.

The same low torque - 7.5 ft-lb - should be used on the bolts that attach the throttle body to the UIM. Just mentioning that because it is in the same area where you found the leak. Also, make sure there is just one smaller o-ring on the bottom of the PCV valve and one large one under the PCV chamber cap.

[MeLLoCeLLo]

As others have pointed out, your symptoms are those of a vacuum leak. One of the bolts for the UIM on the right of the throttle body is actually a stud, IIRC, that requires a larger socket than all the other bolts. I think maybe the bracket for the EGR is attached to it. You will need to remove anything on the stud to properly torque it. 20 in-lb of torque is definitely not enough to seal the UIM. 20 ft-lb is way too much - in fact, the little 6-mm bolts will probably break before they get to 20 ft-lb. The proper torque is 89 in-lb. That's 7-1/2 ft-lb that is pretty easy to get accurately with a 3/8"-drive beam style Craftsman torque wrench that sells for about $25. With a new UIM gasket and a new UIM, you should not need any RTV silicone. Did you follow the instructions in the Techinfo article for changing out the UIM? Sometimes the runners inside the UIM need to be wiggled into place to allow for a good fit of the UIM gasket against the LIM. It will probably be worth your time to pull the UIM and try again. You should not need a new gasket. Buy, borrow, or rent a small torque wrench and buy some blue threadlocker for the UIM bolts. They tend to get loose over time if you don't.

The same low torque - 7.5 ft-lb - should be used on the bolts that attach the throttle body to the UIM. Just mentioning that because it is in the same area where you found the leak. Also, make sure there is just one smaller o-ring on the bottom of the PCV valve and one large one under the PCV chamber cap.

Yes, I did indeed follow the instructions you posted and checked it twice (Never could have done it with them - Thank You).

That bolt you speak of is hopefully the problem because I remember not having a deep socket to properly torque down. I have a friend who is going to let me borrow it, plus I will borrow his torque wrench again. If that doesn't work, I'm going to take the UIM off again and try to line it up as much as possible. Threadlocker ran out when doing the LIM, so I will get some if i need it.

PCV has o-ring, so does the cover.

I want to thank bill buttermore again for the instructions and thank everyone else who gave me some input. I will update here if I have any other questions or when I fix the problem. Cheers!

[MeLLoCeLLo]

Hello again. I had a chance yesterday to look over the UIM again and try to find might be causing the rough idle on my bonne. Turns out after about 30 minutes of close investigation that the EGR corrugated pipe is cracked. The instructions warned about this and I checked, but it wasn't visible from top view of engine bay.

I guess the question now is where do I find this part? I rather buy then have it welded or cemented.

Does anyone know where I could find it? Links or Stores?

Thanks for the help!