Main IndexAuto Repair Home Search Posts SEARCH
POSTS
Who's Online WHO'S
ONLINE
Log in LOG
IN









Search Auto Parts

My Buick idles funny when it is hot


  Email This Post



bethscentury
Novice

Nov 24, 2014, 10:32 AM

Post #1 of 16 (1264 views)
  post locked   My Buick idles funny when it is hot  

Hi car experts, I'm hoping you can help me fix my car. Below is a description of my problem, and things I have already tried--thanks, Beth.

My well maintained 1998 Buick Century, with 160k miles on a GM 3100, is idling funny, but only when warmed up. If I start the car when it is cold, starts fine, runs great. If I start the car when it is already warmed up, like after filling up with gas, then it might not start on the first try. And once it does start easily, or may start and die, and once I get it started the idle goes way up and down. I've tried to fix it myself as I don't have a lot of money, and would like the car to keep running for a few more years. After reading, and trying lots, I came to the conclusion, since it runs so well at other times, that it might not be a serious problem, but a sensor that is giving the car bad info. I read to unplug sensors one at a time to figure out which one might be bad. When I unplug the MAF sensor, the problem goes away--I felt pretty proud that I had figured out what ails the car. I bought a new MAF, installed it, but the problem is still there. Aside from the MAF being bad out of the box, what might be my real issue? Could another sensor or problem be hidden when I unplug the MAF?

What I've tried:
Car has good compression. I tried what I saw on youtube, and sprayed carb cleaner on all the hoses while it was running, to check for vacuum leaks, this did not change the idle speed, and visually, despite their age, they all look good. I have put in new spark plugs and wires. The check engine light is on, but the folks at Autozone say it is only the evap system--I tried a new fuel cap, that didn't make it go away. Could the evap system cause idle problems such as this? And if so, why does unplugging the MAF make the problem go away?
The only problem that exists with the MAF unpluged, is when I first put it in gear to drive, the car loses power when I go to step on the gas, but only the first one or two times, after that car runs totally fine--is this what the car should act like with the MAF unplugged? But if I plug in the MAF, the car doesn't lose power when I first step on the gas, but once heated up and I restart it, it does the crazy idle.

Any help or thoughts are appreciated,
Beth


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 24, 2014, 10:41 AM

Post #2 of 16 (1256 views)
  post locked   Re: My Buick idles funny when it is hot  

If it has a delayed start or acts like it is flooded right after you try to start it after refueling the tank, then you should check to see if the EVAP purge valve is stuck open. With the electrical connector disconnected from the valve, you shouldn't be able to blow through it.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 24, 2014, 10:42 AM

Post #3 of 16 (1255 views)
  post locked   Re: My Buick idles funny when it is hot  

Did Autozone do a code reading for you? If not most do so try again but this time get the code #(s) not the interpretation. Unplugging things will set codes so may need to reset and see what comes back.


Plenty of things possible. If CEL or aka Check Engine Light is staying on there's a hard code and you need that one.


Mean time if you want to clean out throttle body it might help. Also know that resetting codes or disconnecting battery for any reason can cause the car to lose memory on holding an idle well till it "re-learns" to set things back in range for the condition things are in to a point,


T



bethscentury
Novice

Nov 24, 2014, 5:44 PM

Post #4 of 16 (1219 views)
  post locked   Re: My Buick idles funny when it is hot  

"If it has a delayed start or acts like it is flooded right after you try to start it after refueling the tank, then you should check to see if the EVAP purge valve is stuck open. With the electrical connector disconnected from the valve, you shouldn't be able to blow through it."

Thank you for your reply.

It does seem to happen right after I fuel, but I didn't know if this was coincidence, as I think it happens when the car is hot, and I restart it while not at the gas station, the gas station just happens to be the place I start the car shortly after shutting it off. code po442 is triggered, which the gentleman said was evap emission leak detection.

Thanks,
Beth


(This post was edited by bethscentury on Nov 24, 2014, 5:51 PM)


bethscentury
Novice

Nov 24, 2014, 5:49 PM

Post #5 of 16 (1214 views)
  post locked   Re: My Buick idles funny when it is hot  

Thank you for your reply.

"Did Autozone do a code reading for you?"

I went by Advance Auto Parts on my way home.

These codes are stored (but I haven't done the code clearing, so I don't know if they are accurate)

po300 random multiple misfire

po102 maf (I've been unplugging it, so I am sure that is the issue)

PO341
Cam position sensor (I replaced this myself a year or so ago when autozone said that code came up, but didn't unplug the battery, so I don't know if this code is current either, do they go away on their own?)

PO442
Evap Emission leak

PO 440
Evap emissions system.

"Mean time if you want to clean out throttle body it might help. "

I watched a youtube video. I cleaned out the throttle body. And also used the cleaner to check for vacuum leaks which I also saw on a youtube video. Didn't seem to make a difference.

Thank you for all your help again.
Beth


(This post was edited by bethscentury on Nov 24, 2014, 5:51 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 24, 2014, 5:56 PM

Post #6 of 16 (1207 views)
  post locked   Re: My Buick idles funny when it is hot  

You should check that EVAP purge valve for being stuck open. That will cause a P0442 and P0440 codes. If the system is purging when it shouldn't it can make the engine run rich which could cause a funky idle. It is easy to check. You can either blow through it to see if it is sticking open or you can disconnect the purge valve connector and remove the vacuum line that goes from the valve to the charcoal canister and check for vacuum with the engine running. If you have vacuum from the valve or you can blow through it, you should replace it.

The P0300 could be caused from a rich condition due to a purge valve sticking open. A dirty throttle body isn't going to cause EVAP codes.

You really need to clear trouble codes using a scan tool or code reader instead of disconnecting the battery.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 24, 2014, 5:58 PM)


bethscentury
Novice

Nov 24, 2014, 11:48 PM

Post #7 of 16 (1195 views)
  post locked   Re: My Buick idles funny when it is hot  

Wow, that'd be amazing, if that one little thing fixes all the codes, and removes my problem. Thanks. Originally my check engine light came on, and one guy at Autozone called it the gas cap code. I bought a new gas cap--which was pretty different from the one GM gave me to start, so I wondered if that might be why the light didn't go off, that didn't fix the problem, but in talking to them, the evap system didn't sound like it was very important to the running of the car, so I just ignored the check engine light (I almost got the thing fixed just I would know when my check engine light was on for something more serious, but I opted not to).

I live in a cold climate, so I won't be able to work on this until it warms up later in the week, as I don't have a garage. But I'll work finding and checking the EVAP purge valve. Thank you again for pointing me in that direction.

The guy at Advance was nice tonight, and after the scans, and me telling him I had no idea what was wrong, came out to my car, and unplugged some sensors, and said he had no idea what was wrong, as he was surprised that unplugged the MAP, some air temperature sensor that I hadn't heard of, and another air sensor, didn't effect the running of the car at all. In fact, he was really surprised about the MAP, he thought that should cause a stall, but it didn't even change the idle.

Anyway, thank you again. On a warmer day this week I'll try to find the EVAP purge valve, and I'll let you know if that helps.

Happy Thanksgiving,
Beth


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 25, 2014, 3:25 AM

Post #8 of 16 (1188 views)
  post locked   Re: My Buick idles funny when it is hot  


Quote
The guy at Advance was nice tonight, and after the scans, and me telling him I had no idea what was wrong, came out to my car, and unplugged some sensors, and said he had no idea what was wrong,


That pretty much says it all. Only an idiot would try to diagnose a car by unplugging sensors and those guys sure qualify for that name. They are just parts salespeople parading as someone that knows something.

Thanks to them you can't trust anything you see in the computer. At this point the computer needs to be cleared and start over.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Nov 25, 2014, 3:46 AM)


bethscentury
Novice

Nov 30, 2014, 3:22 PM

Post #9 of 16 (1119 views)
  post locked   Re: My Buick idles funny when it is hot  

Additional info: I went to get the Evap Purge valve, but they didn't have it, which sucks, because tomorrow it will be cold again. Anyway, they ordered it. I checked the PCV valve, it was clogged with light brown sludge--I've read that this is bad, and most likely coolant, but could it be gas or something else? My coolant isn't low. I'm marking the overflow thingy, and checking the radiator wasn't low. Could it be gas causing this light brown stuff?

Thanks again,
Beth


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 30, 2014, 3:35 PM

Post #10 of 16 (1118 views)
  post locked   Re: My Buick idles funny when it is hot  

That's just oil sludge and normal.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 30, 2014, 4:07 PM

Post #11 of 16 (1114 views)
  post locked   Re: My Buick idles funny when it is hot  

Did the old purge valve test bad?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 30, 2014, 4:15 PM

Post #12 of 16 (1112 views)
  post locked   Re: My Buick idles funny when it is hot  


Quote
Did the old purge valve test bad?


Hahaha .............. yeah....right



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 30, 2014, 4:30 PM

Post #13 of 16 (1110 views)
  post locked   Re: My Buick idles funny when it is hot  

Well, it never hurts to ask. The symptoms point to a stuck open purge valve, but I want to state that I am not absolutely saying without a doubt that it is the culprit unless you test it and it proves faulty.


Quote
In fact, he was really surprised about the MAP, he thought that should cause a stall, but it didn't even change the idle.


If you want to wow the wantabe at the parts store, tell him unplugging a MAP sensor on a MAF system won't have an affect because the MAP sensor on a MAF system is used for baro readings, detecting EGR operation, and used as a back up if the MAF faults.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 30, 2014, 4:37 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 1, 2014, 5:04 AM

Post #14 of 16 (1091 views)
  post locked   Re: My Buick idles funny when it is hot  

Quote from post #9 ">> I checked the PCV valve, it was clogged with light brown sludge--I've read that this is bad, and most likely coolant, but could it be gas or something else? My coolant isn't low.<<"


There's a clue there. Need to know was PCV really clogged as in no vacuum or flow at all? Did you clean that up or just leave it that way? Could be from condensation in certain conditions but more likely neglect or coolant is in fact getting into the oil. Depending on where and how you change oil could be a reason coolant isn't low. These Quickie Lube places top off fluids and you might not know it's slowly consuming coolant?


I only find condensation of the sort if this is a lot like a thick milky/brown on vehicles exposed to several conditions all at once continuously such as wild temp and humidity swings, vehicle left parked OUTDOORS for more than a day or two routinely and lots or all short trips when it is used and throw in just not changing oil often enough at all.


It could be either THE problem or the result of another problem but not good. You may find same goo on dipstick and under oil filler cap.


Not certain at all if this is causing your current complaint but it deserves attention or it will be the problem,


T



bethscentury
Novice

Jan 1, 2015, 5:34 PM

Post #15 of 16 (954 views)
  post locked   Re: My Buick idles funny when it is hot  

Thank you all for your help and suggestions. I gave up and bought a new (used) car. It is cold out, I don't have a garage, scanner, knowledge, money to try to fix my old car. I'm just going to try to sell it cheap, or if nobody wants it I'm told it has several hundred dollars in scrap value.

Thank you all again,
Beth


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 2, 2015, 2:17 AM

Post #16 of 16 (946 views)
  post locked   Re: My Buick idles funny when it is hot  

OK - done with that car and good luck with the next. Yes - it has scrap value that varies place to place and what is still "good" on it for parts but probably do better selling it as a used car privately and just be honest about it condition as you know it.


I'll close this out to keep spammers away and YOU may ask to re-open it if you wish by any moderator,


T







  Email This Post
 
 


Feed Button




Search for (options) Privacy Sitemap