** Won't idle - Help before I start it on Fire!!!!

BuickTurboSix

BuickTurboSix

Member
Joined
May 25, 2001
I have a 85 Regal V8 that is giving me trouble. It won't idle. Dies out at the stop sign. Seems AOK if it is going down the road. And, once in a great while, idles ok for a period of time! At idle, if I put my hand over the carb, it will settle out. It is like there is a vacuum leak, but I sure can't find one. Pull the MCS plug and it will run fine too.

Here is what I have done. TPS was open, new one installed. New Air-Horn gasket. After the TPS was installed and the several days later, I put the OTC on it again and it showed a 13 and a 44. Cleared them and they have not come back, so I don't know if they are real or not.

In Mode 5, the MCS (mixture Control Solenoid) dwell goes from 4 to 45, but never sees the over 50 that all the manuals talk about. O2 sensor works. I see the output change when I do a load & choke test. But, I don't know if it is marginal in output. Reads .250 in lean condition and goes to 1.050 for rich.

Also, I don't know what to expect when I display Mode 4. What should the cross counts look like?

Getting the idea I am lost. What I don't get is - Is it screwed up because the O2 is reading lean and messing everything up, or is the O2 reading accurate for and indicating some other problem?? Any great ideas???? Very low mile car - 18,000. It's a sweetheart, but driving me crazzzzzzzzy! Help me fix this and I will surprise you with something in the mail!!! I don't want to break down and take it in!!!!

Thanks - Tom
 
sounds to me none a that was necessary... u sccould and prob are ideling way too low.. bring the idel up ... it should be 600-700rpm in gear... 700-800 not in gear. but 1st things first... check ur timing... after that do u fuel mixture.. then get to the idel controll.
 
TTTT

You message was very criptic - But what I think you said was "None of that was needed"..... If so, I don't understand your point. An open in the TPS is a required repair. New Airhorn gasket - just a good idea as it stuck hard when opened to replace the TPS. The rest of what I wrote is just tests and data for informational purposes.

Really need help guys. Where is all the Techs out there!! :eek:)

Thanks in advance.

Tom:rolleyes:
 
When you replaced the TPS did you change the setting on the screw at the air horn(cann't remeber what it's called)
Also check the coolant sensor to make sure that it's connected good.
What setting is the TPS at?
Check your maps.
Use a hose with a small funnel at the end. Put the funnel end to your ear and use the hose end all around your hoses. You will hear a hissing sound at a leak.
Others use soapy water or propane.
 
TPS

Yes, the TPS is adjusted correctly. It was fun getting the plug out, but I finally managed. Book says .48 +-.04. I am right in there. No opens in it now. You can see it operate correctly. So, I will look a little harder for a leak. One person has suggested the MCS. It seems to be working, but, maybe it is not working right. I suppose that is always a possibility. How could you tell it it was stuck in the lean condition too much of the time. If that was true, it would fit the nature of this problem. HMMMMM - has me thinking. It is kind of a hard device to trouble shoot.

Coolant sensor seems AOK - OTC shows the gradual warm up and final temp running at about 205 degrees. Is that all I am looking for, or is there a separate switch to concern myself with?
 
Not all vacuum leaks occur within the hoses or at connection. Sometimes a device like the EGR can leak.

I found a leaking EGR and an actuautor by disconnecting their hoses, hooking up another new, clean hose and sucking on it like a straw. A leaking device is a double whammy. It doesn't work and it can cause a big vacuum leak.
 
Progress!!! But still not there!

OK - I am part way there. I put new O-Rings in the Air Bleed assembly, new O2 sensor. Readjusted things and it will now run when it is warmed up AOK. But for the 1st couple minutes when the ECM has it in Open Loop - Rich mode, it will stumble and quit. As soon as it goes Closed Loop and starts leaning the MCS, it settles out. What is the last piece of the puzzle? Also, what is the correct setting of the stop screw?? If the Air Bleed adjusts the idle, what is the stop used for?
Thx, Tom
 
A little known fact about troubleshooting the CCC system is that if one runs the vehicle at idle for an extended period of time it will go into an 'open loop' operation.

This is caused by the engine running cooler at the extended idle causing the tempurature on the oxygen sensor to drop lower than 600 degrees F. This results in no reading because the sensor needs to be above 600. On extreme cases like mine, it causes the ECM to run the engine at a partial 'open loop' operation. This is a fixed lean command with no dwell reading, and either a code 13 or 44 'CHECK ENGINE' result. Although it is suggested that revving the engine for over 2 minutes at hi RPM's will put the vehicle back into 'closed loop' operation, this at best will not always work. One's best bet is to wait till the next day and limit the diagnostic time.

Your other problems are all related to the carburetor. Take your time installing the air horn correctly. As for ther air bleed, you should of left it alone. ECM carburators are troublesome to adjust or repair. A spare carb gives you time to patiently and properly adjust and rebuild if it is needed..... :D
 
TTT

TTT

Still looking for help on the last questions. See my last post.


Lower O-ring was shot on the AIR Bleed. So this was a no brainer.

TPS was open, also a no brainer.

O2 was showing marginal reading and irratic behavior. Replacement instantly corrected readings and provided predictable\expected results.

I believe all corrective actions have been possitive to this point. Just looking for the rest of the puzzle to be solved.

Thanks to all for the help!!! Tom
 
have you checked the adjustment of the choke?sounds like it might not be opening up at start up.(poss. bad choke pull-off)but as car warms it eventually opens and car runs fine.you didn't state when ir how it stumbles.just when you first start it and it stalls right away or are you starting it and trying to drive it rightaway.do you have to hold the gas pedal to keep it running until its warmed up so it wont stall or does that even matter if you do.if you could be more specific on when,were,how long ,and what you do to keep it going until it runs o.k. would be helpfull with out actually being able to see it.(paint me a pitchure)and i will do my best to help.what is the dwell reading on the mcs when it's cold and while it warms and have you played with the adjustments?
 
Details of current problem

Car is warmed up, but sat off for 5 min. (Milk run to the store) and when you restart it, it will stumble and quit right away while you are sitting still. Yes, you can keep is running by tickling the trottle. With the OTC2000 on it, you can see it is in rich mode for starting. After about 2.5 minutes, you see it switch to lean mode and the idle will settle out and keep running fine. I think that is about everything. Oh yes, and if you put your had over the choke, it smooths out. Pull off is working correctly, so it would not be that.

Still have not got an answer to the correct setting of the Idle stop screw.

Thx, Tom
 
3 - 4 turns from bottom should get you close. I have played with it before and have regretted it, I'm about to take it to a mech. I had problems with the bottom O ring as well, I broke 3 just trying to reinstall a new one. I found that if you use a lit coating of oil on the seal before install that it installs with out breaking.
Make sure that the Cap is seated right on the disp. This as well will give you a bad idle.
 
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