jeffreyalman

hey Allan stupid question - does it only drop with foot on the brake? The reason I ask is that this a.m. I had the wagon in for the 3rd master cylinder in a year and my mechanic thought the booster may be going.

he said keep my eye on it, tell tale sign would be rough idle because of vacuum leak in power brake booster.

Allan R

Jeffrey,
Not a dumb question. Yes, that's when its noticed, because I have to keep brake pressure when stopped to avoid introducing the front of my car to the bumper of the car in front. If I take my foot off the brake the car will start rolling and subsequently the rpms increase with a little speed. ( I'm sorry Jeff, couldn't resist that)

If I slip the car into N at a light and take my foot off the brake (not a really safe thing to do on todays streets) the rpms are steady at a low reading of around 730. I did have the master cylinder / reservoir replaced back in Jan 2005 when it failed. To my knowledge, that's the first replacement since it was built in 1994. Braking efficiency is 100% at this time.

I think that's the same thing meoff was alluding to in the previous post.

70 cutlass s

The booster has an diaphragm in it. Brake fluid can eat away at it. So if one of the master cylinders had a leak and fluid got in the booster than it could be going bad.

Since you have vacuum going to it. Than yes if it has a hole in the diaphragm than it would have a rough idle. Just becarefull if it does fail than your car would be hard to stop if the booster fails.

jeffreyalman

the other symptom of a bad brake booster is a hard pedal, like no power brakes. My brake pedal had been sinking at a red light in gear (my idle is a little high - I like it like that) and after the 2nd master cylinder to cure it, he suggested the booster. the 2nd master lasted a couple of months, then the sinking pedal again. so today the 3rd (different make)
I feel the pedal is lower than the other 2 cars anyway, and I have always used 2 feet to stop, but I attribute that to the shear bulk of this cruise ship. In any event, just some more possibilities.

meoff

I you only see 10 rpm drop and no missing like a large vaccum leak then I would think it's OK.
and the champion plugs are a personal issue that I have never liked them in a G/M.I found too many problems that were related.
the fact that G/M used A/C in that engine for years and I am biased!
anytime I had a driveability complaint and seen champion plugs-they were the first to go.I remember we had a rash of bad A/C delco's though I think in 88 or 89 and car would have a miss at idle and found culprit to be the tiny ceramic cone at the electrode had broken and slid down covering where you would normally set gap.could see the odd cylinder pretty good on an ociliscope.new set of A/C Delco's and was good to go!

Allan R

Ok, thx on that. The idle drops a max of 20 rpms when the brake is on which is minimal in my opinion. If there was a big vacuum leak because of the brake diaphram that would also cause the engine speed to increase instead of decrease.

I was just out at the car looking for the idle set screw (as you described in your post). I think I found it, but am not 100% sure. I took a picture and labeled where I think it is. Please confirm. It appears to do double duty with one of the throttle spring attachment points???
If it is what is in the picture, I should be able to tweak it without touching the cable bracket.
Idleset-1.jpg?t=1266273741

meoff

NO! do not break that as you will be buying parts!that is just a throttle spring retainer!pull the plastic cover on the right and give me another pic or 2 at different angles where the cover was and can tell you where to look.will look at the 90 olds saturday and give you a better idea.but off memory I don't recall where in relation to the IAC and MAF and Throttle spring as in your pics

Allan R

I went and looked at the tb and linkages. There's absolutely nothing on the back of the tb that even remotely has a factory seal. I'm now wondering about the "tower" that's plugged on the top of the tb. If it has the set screw underneath, do you have to re-seal it after adjusting?

I didn't take the metal throttle cable protector off because I can get a pretty good shot from behind with it still on.

IMG_1213.jpg?t=1266697473

What I'm thinking now is that the adjustment screw is in here....What do you think? I know you said your 3800 was a 90 which is a series 1. This is a series 2, so they might have "refined" some areas to make it easier to work on???? After looking really really carefully at the tb, I just can't find anything that is capped or accessible for any type of adjustment on the tb..

Idleset-2.jpg?t=1266697867

meoff

how about a couple of pics at different angles and not zoomed in so close.and a couple shots zoomed in like you are with a couple angles at the plug in question.I know you can see fine with the cover on but from my chair here had a hard time referencing the throttle to the plug in question as the cover was hiding the view.I do think that is the plug but don't want to say yes and you pop it and have coolant dumping out!

Allan R

No problem,
Here's some shots of the car showing the tb and what I think is the set screw tower.

IMG_1182-1.jpg?t=1266721797


In this pic (when I took off the tb for cleaning) the coolant jacket has just the tiniest bit of cutout at the bottom of the chamber below the air intake.

IMG_1168-1.jpg?t=1266722704

meoff

the plug you are pointing out looks way too bigand has been many years since I worked on those to go off memory.I'll hit local salvage yards this weekend and look at one and let you know for sureI do remember that they had a lot of probs with that egr setup but if I remember correctly you already replaced that.

Allan R

Haven't touched the EGR. I understand that if it's not working properly, the engine will stay at high idle or quit entirely. I'll try hitting the boneyard too. Maybe between the 2 of us, we'll be able to find out what's under that cap. It's not that big actually. ID size is about 3/4 inch. It's the only thing I can find anywhere on the tb that has the potential to cover the set screw. Let's compare notes on the weekend. Cheers!

Olds64

Allan, sorry I haven't contributed recently. I haven't had any ideas.

If you haven't done anything to the EGR then perhaps you should troubleshoot it. If your EGR valve isn't working properly then that could cause a poor idle. If the EGR valve is supposed to be closed but leaks a little inert exhaust gas into the combustion chamber then you will have improper combustion and poor idle. Just a thought...

Allan R

meoff,
About the top engine and fuel injector cleaner. The stuff that I got from the GM dealer said it was mostly used by techs in the shop. They have to mix it with gas to do fuel injector cleaning and/or use a special line to inject it? Sounds like hooey to me.

It looks like this:


I suspect that there may be a fair bit of carbon build up on the valves which may be causing part of the problem with the idle. (look back at the pics I posted of the tb before I took it off and cleaned it. There's probably a good chance the valves and cylinder heads might look like that too) Looking back at this whole process, I wish I'd just tried this stuff first and gone from there. On the other hand, I've learned a LOT about my car and got a chance to get my hands dirty. Kind of creates a bond between machine and man so to speak.

Anyway, I looked up how to use this stuff on the web and it shows a video of pouring it directly into the brake booster vacuum line. Its not a spray like you described in post 32. While the engine is warmed up and running they disconnect the vacuum line from the brake booster and pour it in through there. (this was shown on a 1998 Buick 3800 series 2 with supercharger). Does this way to use it sound safe to you? My only worry is that with the car having high mileage (180000+) would this cause any damage to the valves or rings? I know that I'll have to change oil right after using this stuff. They don't recomend driving more than 100 miles afterwards without doing an oil change. Also claims it wont hurt the O2 sensors.

Is seafoam the same stuff???? Not sure if I can get it here. But I'm willing to give this a shot if it's the right stuff.

Olds64

Allan, that stuff sounds like Seafoam or the Berrymans engine clean you can get at the auto parts store. I've also heard you can pour ATF into your engine while it is running to do the same thing (sounds redneck to me). FWIW, Seafoam and Berrymans are both big names in engine additives. I would give it a shot especially since it is only about $12 a bottle here in OK.

Allan R

Hey Jesse,
Got a can of seafoam today. 13.00 - so it's about the same as what you pay. I've never used it before so I'm naturally a little hesitant, but what the heck. Nothing ventured nothing gained. I've read lots of good things and lots of horror stories about it, so I guess it's really my choice.

Any tips on using it? The guy at Partsource says to use only half of it on the top end, anything more is a waste of product. Said the stuff works instantly. If used in the crankcase, change oil really soon cause it thins the oil too much.

I'm all set to smoke up the cul de sac tommorrow after I hear back. Right now, it's back to the 2010 Olympics coverage...duh...Mens Curling semi finals....Team Martin better not dissappoint or he'll never hear the end of it. He curls out of our club at the Saville Sports Centre here in Edmonton.

Olds64

Allan, I've heard similar stories. Definitely read the directions. If it says to add the whole can to the engine then you can always add half, drive the car around for ahwile, and then add the last of it later. I hope it works.

mugzilla

Pour in 1/2 slowly, let sit till cool, pour in rest slowly . Bomb down highway and blow it out ...

Allan R

Well, I followed the instructions on the can to the letter. Car warmed up (gave it a 10 mile run) and back in the driveway.

Left it running and popped the hood. Disconnected the brake booster vacuum line (crap, the engine almost died then it adjusted and ran ok). Slowly I poured in 1/3 of the bottle as per instructions. Gotta say my heart was beating a little faster when I did this cause I didn't know if I was helping or hurting the engine. Anyway, as I continued pouring in the SeaFoam, the engine rpm started to increase a bit. It seemed to be drinking this like hi test gas!!). I plugged the vacuum line back onto the brake booster and the engine died. So I let it sit for 10 minutes and fired it back up. Took a few extra cranks, but it started and ran. ABSOLUTELY NO SMOKE AT ALL. That is just so wrong compared to what SeaFoam claimed would happen, and what I've seen in SeaFoam videos. So I dosed it again with another 1/3 of the can and waited again.

Exactly the same results. Nothing. The valve train does sound a little quieter, but I don't know if that's just cause I'm hoping to hear and see some improvement.

I dumped the remaining 1/3 can into the crankcase. I'll change the oil tommorrow because it's recommended not to run more than 100 miles with SeaFoam in already dirty oil.

I went outside just now (over 2 hours since I added this stuff) and fired up ol Josie. Started just fine. Sounds smooth. Same issue with the idle speed. It's still down around 650 in drive, and about 730 in park.

Can anyone out there with a 3800 series 2 tell me what their engine idles at? Here's what I'm looking for comparisons on:

Cold start: 1250 rpms and gradually slows down as warm up progresses.
Engine hot / in drive: 650 rpm
Engine hot / in park: 730 rpm

Eric Anderson

FWIW I know a guy here that used to own the now defunct Olds dealersip he swore by the top engine cleaner you showed. Also I have a truck that was having the same problems you are describing, it would run fine at startup then when it would warm up and the rpm's would settle down it would idle a little poorly. It continued to get worse over the course of a year or so until it was to the point at a stop you would have to put it in N and even feather the gas a little. I checked all of the usual suspects like you, vac leaks sensors plugs wires etc...etc..., did nothing. Took it to the dealer they screwed with the throttle body said they fixed it and at that time they checked the fuel pressure as did I and it was good a week later same thing again. Took it back they checked everything again and decided it needed a new throttle body, big buck$ , any way one of the mechs. there asked me if I wanted to try a new fuel pump, I never suspected it nor did they as the pressure was testing good and it ran like a champ under throttle but due to the price difference between that and the new throttle body I told him to go ahead, fixed it runs like new. I can't say thats your problem but if all else fails...

Allan R

Interesting. The fuel pump at both rails is good though. If the fuel pump wasn't doing its job, the pressure would read low. Maybe I'll try changing the fuel filter first and see what happens. They're a whole lot cheaper and easier to do than a pump. I'll let you know what happens.

Eric Anderson

Right I had checked the fuel pressure also as did the dealer on its first trip in, it read good both times. The first time in they adjusted the idle, didn't fix it. I'm not sure what made the mech. suggest the fuel pump change but I'm glad he did, I was going nuts looking for a throttle body for the thing its a 3500hd with a 454 the only place I could find one was the dealer and I think it must have been made of platinum. I don't know what exactly the problem was with the pump, probably should have tried to find out. The fuel filter is worth a try, if nothing else it's cheap, easy and needs to be done anyway good luck with it Allan.

Olds64

Let us know what happens when you put it a new fuel filter. It won't hurt anything.

Allan R

Ok, here's the latest update:

There is NO WAY to adjust the idle without going through the ECM (aka ECU or PCM). So I thought the ECM might be faulty. Yes, it can go wonky according to info on the web.

I called Gary over at Wheatons Chev (used to be Olds) and told him what the problem was and all the things I've done over the last few months to try and fix this. He said: "Sounds a lot like you've got a faulty coolant temp sensor".
"No way" I countered. "Wouldn't that show up on the OBD11 as a problem when checking the oil, trans and coolant temps?
"Not necessarily" he said, and he also said he had a car in the shop doing the same thing mine was doing. His driveability tech is off due to shoulder surgery and won't be back for about 5 months. Drat!

Anyway, I did some thinking about what he said. Now where is the coolant temp sensor? It's wrapped with a heat shield just below the throttle body, next to the exhaust. It was too hot to work on, but what I did was lift the harness a little to check if it was the right one. Yup.

Then I came inside and phoned Partsource. They have the sensor and it's only 33.88. I figured I would drop over and pick it up. According to GM if the resistance in the sensor should be about 10000 ohms when cold and 200 ohms when hot. This makes sense because the higher the resistance at startup forces the loop to stay closed. As temp increases the loop opens as the resistance goes down.

This morning I started ol Betsy and headed out. Got to my first red light about 5 minutes later. The car was showing all light bars on the dash indicating it had reached operating temp. Stopped at the light and looked at the digital tach. 710 (no not the oil thingy) then 700. It stayed pegged at 700!! Next red light, same thing. Parked in my stall at work - same thing. Waited for the drive home. Held my breath at the first red light. 700 and holding. The stumble appears to be gone. Engine is running fine and rpms are back.

I believe the 2 contacts on the sensor were either loose or have corrosion on them. Saturday I'm going to pull the connector off and clean it up with some electrical cleaner and put it back on.

One last thing: If any of you ever get that awkward "nothing happened" when I turned the key feeling. Then I tried again and the engine started???
It's the battery connections!!!! Make sure they're really tight. The cables should not be able to move even a little.

So we can put this thread to bed. Problem finally solved. If I'd known then what I know now, this would have cost me nothing. But now I also know a heck of a lot more about my car.

Thank you to all who contributed suggestions and encouragement to help get this idle problem solved. C.O. is the BEST!!!

Eric Anderson

Temp sensor... how about that. Glad to hear you got it solved Allan.

Olds64

Oh yeah!

The Olds lives to drive another few years.

Allan R

thx Eric,
Not what I thought it would be either. Jeez, they put it in the stupidest place too, right next to a hot exhaust???? Gotta get an engineering degree and become smart like that!

Got a road trip coming up on Monday next week. It'll be interesting to see if the seafoam treatment I put through the intake and the fuel injector cleaner in the tank will have any effect.. oh yeah, gotta change the oil on Sat. It still has 1/3 of a can of seafoam in it and I'm not willing to chance it on the highway. Might be totally ok, but heck I've got about 3500 miles on the oil it it right now anyway. Spring cleanin in the Olds engine!!

Olds64

Let us know how the road trip goes.

70 cutlass s

I call shot gun.

Allan R

Anytime Andy. You'd always be welcome.

Oldsguy

Reviving this old thread because I just had a relevant experience. See post #34 picture six first. See those boots? My '99 Buick LeSabre with the same 3800 series II engine started developing a terrible driveability issue. It would not idle well and would die if put in drive. It finally threw a P0171 code which is running lean on bank #1. Jesse (Olds64) IS here for the weekend and we decided to look for vacuum leaks this morning and in about five seconds after removing the plastic cover he saw it. The boot was completely off the nipple on the intake manifold. Talk about a serious vacuum leak! Put the boot back on, went to the auto store to clear the code, and the car has been running fine all day! Yeah!!!

Allan R

Glad to hear your car is up and running again Dan. Those boots are easy to get from GM. They still have them as stocking parts and sell for 5 bucks for the 2 tee and 11 bucks for the right angle tee. I bought new ones for my car during this fix.

Oldsguy

Excellent! Thanks