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Discussion Starter #1 (Edited)
My 2000 Buick Lesabre has had a few sensors replaced due to PO 171 problems ... and I replaced the ICM because it would die and not start until the temp of the engine dropped ... MAF sensor replaced ...

When it's running ... the car runs fine ... except for intermittent stalling while driving and unable to re-start sometimes unless you hold the idle higher.. and sometimes I have to go through 2 to 10 turnovers and restarts for the idle to stabilize and keep the engine running at idle ...

Noticed the idle between 600 and 900 ... higher on cold start..

Sometimes it will run for miles, hours without a problem ... with or without AC on ... and then poof ... out of the blue stalling and not able to hold an idle ... and when I coasting too ... and I throw it into neutral, turn the key to restart and back to drive to continue ... very dangerous

I used to hear a little pressure released when removing Gas cap and I also had a Check Gas Cap message too ... replaced Gas Cap message went away ... put old cap on ... message hasn't returned ... phantom message ...??

So if I don't hear a pressure release (sounds like vacuum sucking) when I take the gas cap off does that mean there is a leak somewhere in the evap emissions ... I took the evap tubing off the purge solenoid and can blow through the tube down to the evap canister without resistance and it smells like gas vapors in the tube ... don't know if this is right or not ...

Fuel pressure regulator vacuum line has no fuel in it ... the vacuum lines on top of the engine appear solid ... idle doesn't change when spraying starter fluid etc. over tubes ...

So no I'm wondering what the intermittent stalling could be ... as you can read above I've done a lot of different back yard test and replacements ... just trying to resolve the issue because it is dangerous when the car shuts off while driving especiall on rotaries ...

Ed
 

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From what you have done and said, it probualy a fuel injector problem. As its only lean in bank one, i would check the fuel injectors on that side for problems. First make sure the engine is cool, less then 90 F. Get a muti meter and set it on ohms, disconnect the the plug. All of them should read around 11.4-12.6 ohms.
 

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The evap system can sometimes include an air pump that will suck the fumes out of the tank and into a charcoal canister and I think that can cause a small vacuum so the pressure release noise at the gas cap can definitely be normal. If the injectors as mentioned are all within resistance specs could possibly be a vacuum leak of some sort on one side of the engine causing the lean condition on just that one side.
 

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Discussion Starter #4
Thanks buccanner ... I did find that the fuel pressure was 50 on prime and then goes down to 40 and holds there ... turn ignition to off and holds ... no fuel pressure leak ...

Today ... I had it out and ran fine until I stopped and shut it off ... took a while but playing two feet (brake and gas) in drive ... to keep the idle was the only way ... I was stalling while driving ... got to my moms and shut it off ... wouldn't start again ... then the two feet ... and drove it home ... sut it off ... restarted from outside of car twice ... and kept the idle around 900 ... sort of a mystery how it wants to be on it's own ...

But I will try the injectors and measure the ohms on each one ...

I'm driving this car to Utica tomorrow ... lol ... because I have a rental but I didn't want my wife to a have to deal with the issues and a long 560 mile round trip might do something ... lol

I'll post everything I find ... Ed
 

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Discussion Starter #5
Thanks carfanatic (Adam) and buccaneer (Rob) ... I will try ... there is a air pump ... don't know where it goes and it has like a hat on it with a filter ...

I tried to eliminate the entire emissions return by removing the intake vacuum lines off the inlet and plugged it with a vacuum plug ... and it still had issues ... I'll try again to eliminate the carbon canister ... and fuel pressure seems normal ...

Right now check engine light is on which was 80% on until I changed the Temperature sensor on the block ... now I don't get any emissions related codes ...

Will try anything before spending any more $$ ... I was going to take the TPS sensor out and clean it ... it's not throwing a code but may be flaky ... there is a lot of carbon built up ...

Sorry for the long windedness ... it would be better in person and over a glass of cold something ...
 

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You say you removed the intake vacuum lines off the inlet? I wouldn't eliminate the carbon canister... all it does it absorb and hold the excess fuel vapors from the tank until the PCM tells the EVAP purge solenoid to purge them so they aren't vented into the atmosphere. If the ECT sensor fixed the emissions codes I wouldn't worry about the EVAP now. As for the TPS sensor, I know a lot of them are sealed units and just connect to the throttle blade. Could be a bad sensor, worn winding inside and losing signal at a certain throttle % so the PCM thinks the throttle blade is closed at that point?
 

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Discussion Starter #7
Thanks Adam ... I only eliminated the canister to experiment trying to eliminate a potential vacuum leak ... it's all back together ...

I will check the throttle position sensor ...

There is also a secondary air supply to the egr via a solenoid and vacuum ... towards the rear of engine ... will have a look ...

I found these diagrams ... if you click on the picture it shows a detailed view of the components you don't normally see as a consumer ...

Buick 2000Lesabre Car parts for your Buick, Cadillac, Chevrolet, Hummer, Light Truck, Oldsmobile, Pontiac, and more!

I'll keep trying to eliminate one thing at a time ...!!
 

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Discussion Starter #8
Ok ... I'm narrowing it down ... a little ...

There is that secondary solenoid that controls vacuum to the egr secondary air valve ... in the tubing coming from the solenoid there is a check valve so the vacuum only goes in one direction ... and it goes to a tubing connector at a junction at the top of the engine block ....

With this tubing disconnected it will fire up just by turning the key ... when I reconnect it and try to start it ... no go ... car dies immediately ... so if I block this vacuum port it stalls ... so I piece by piece put back the tubing after starting the car until I get a complete connection and the car doesn't stall ... not sure how that does it ... but I'm going to buy all new tubing and connectors ...

I did replace the PCV valve and there is good vaccum at the tubing connector on the block ... so I'm stumped as to why if I block of this vacuum port does the car die ...

Maybe I'm missing something ...
 

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any FWD 3800 only has one bank. Everything is Bank 1.

It's not your engine cooling down, it's your fuel pump. It's old and clogged with sh!t or is worn out and overheating. Replace it. There's no engine part that shuts down on being hot unless you have an outboard off a boat.

the EVAP system is a pressure based system than opens a valve beyond something like .5psi and burns it through a nipple on the TB. It will not stall your car and you can safely remove the entire thing with 0 consequences if you cap everything right and remove the codes.

There are a very limited number of sensors that will keep your car from running. They are the MAF, o2, MAP, crank and cam. Everything else is just a emissions or "glamor" sensor. Furthermore the only thing that quits out when it gets hot is the fuel pump on these vehicles, unless you have a bad wire that kinks as it warms up. If that were the case it would stay in its kinked, voltage blocking position until moved.
 

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Discussion Starter #10
thanks ... I did have on engine part ... ICM that would heat up and kill the engine ... when the engine temp dropped to 130F it would start again until temp rose ...

But I do understand that the fuel pump could be the "heating" culprit ... but I get a solid 50psi on prime and 40+ held after prime ...

Cam sensor replaced when it threw a 341 code

Maf replaced (didn't need to) for 171 code

ECT sensor replaced for 118 .. now no service engine light at all ...

Disconnected MAP sensor ... electrically and physically from the pcv valve port and did not get a code ... wondered why a code wasn't set for the MAP ... car will start everytime the pcv valve port is open and hold the idle ... put map back in ... it won't hold an idle unless you hold the pedal down ... but that is any engine intake vacuum line ...

So I don't know why a map code wasn't set ... may try another MAP (from junkie) before I spend $50 on a new one ... !!!
 

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the ICM is built into the PCM unless you're running a spark box. Also the ignition coils are pretty well isolated from the engine.

PSI from the pump don't matter if the pump is old and junky. As far as your map codes and your intermittent issues, a bad power lead from the MAP, MAF or o2 sensor would cause this.

MAF and MAP sensors can throw each other off and cause issues. While looking at one, also look at the other.
 

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Discussion Starter #12
thanks ... impOster ... I'll look at the supply voltage and wiring ...

I drove the car 282 miles ... ran excellent and got good mileage ... but if I stopped ... it wouldn't start ... just like in the driveway ...

And I'm driving it back on Friday ... the same distance ...!!

So I will try a couple of things as you mentioned ...
 

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I have a 96 Park Ave Vin K with a 3800 Series II, and I have had the problem you are describing here for 3 years on and off, no mechanic could find the problem, of course they were not GM Mechanics...

Finally my rough idle cause a coil pack to fail, after replacing it ran fine till I let it idle and cut the AC on, then it finally died for good, this was about 2+ months ago..

I won't add anything else, I'll eventually start my own thread, because i do not want to hijack this one, I will be watching the thread though.

Hope you get the issue figured out!
 
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