1988 Buick century limited

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  #1  
Old 04-25-08, 07:02 AM
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Question 1988 Buick century limited

My father has given me a 1988 buick century limited, V6, 3.8 liter engine. It is a family car going from grandma to my dad to me. The trouble is... When cold the car needs to idle with foot on accelerator with a high idle for about 5 minutes before it will idle and not stall. It also needs to idle for another 5 or so minutes to completely warm up... otherwise when you try to accelerate from a stop it does nothing for like 5 to 10 seconds and then it takes off, like normal. Once the car is warm it runs perfect no problems. Basically takes 4 or more hours for the car to be cold enough to behave this way when starting again. Dad has replaced the fuel injectors, tune up... when I received the car I had a diagnostic run and replaced the ignition module; it does now run on all six The next code issues are T-code 32 and 44. EGR valve or solenoid. I am not sure that these would cause this problem; I am inclined to think it is a vacuum issue. Where is the EGR valve and solenoid. Could I replace these myself? To save money I don't have to begin with. Also does my problem sound like anything else you have experienced before? Any ideas or assistance would be immensely appreciated. Thanks, Dawn
 

Last edited by dmhartley; 04-25-08 at 07:04 AM. Reason: spelling
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  #2  
Old 04-25-08, 08:52 AM
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coolant temperature is the primary input for cold start up and operation. I'd suspect a temp sensor out of range...in other words, the computer thinks it's warmer then it really is and therefore does not supply enough fuel.

If the EGR were to be stuck open, you'd certainly have driveability problems, but they wouldn't clear up and be fine when warm.

Concentrate on the cold start issue first by either having someone scan the computer when it's cold...preferably after an overnight soak (not a rain storm! ) to see if the sensor is out of range. or, if you are a gambler, you could just install a new coolant sensor...15-25 bucks. the other thing i would check is the throttle blade for deposit buildup. remove the rubber snorkle tube from the air cleaner housing/MAF sensor and throttle body opening...open the htrottle and look inside with a flashlight...the underside of the throttle blade may be covered with a thick layer of black carbon and this will also cause idle concerns...in extreme cases, it can cause other driveability concerns.

the EGR valve is DIY serviceable...let's get your cold start thingy taken care of and then go after the codes...
 
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Old 04-25-08, 09:15 AM
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Talking Thank you

Thank you very very much! I will attempt this tomorrow and keep you posted of my success!
 
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Old 04-25-08, 10:59 AM
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is it a fuel injected or carburated model? i can speak only of 1984 that i had - and with smilar issue - but i can't find 3.8L V6 specs for that year. and in 4 yrs of difference they might have gone to FI engine, though i have seen 1991 carburated ones.
my knowledge is for carburated one.
sounds like idle speed control module or unit or whatever is it called is not doing its job and you are taking over with your foot on the gas pedal. i had exactly, down to iota, same issue with my 87 taurus, and it was ISCU, solenoid type.
i think you have 2.8 liter engine.
 
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Old 04-25-08, 11:12 AM
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Fuel injected after '86.
 
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Old 04-25-08, 12:12 PM
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Originally Posted by the_tow_guy View Post
Fuel injected after '86.
good to know. then my carburated experience is not applicable. thank you.
i still think i's idle speed control device. though i understand science behind the temp sensor influencing ECM, somehow i do not feel that the difference should be great enough to cause that much of a trouble. unless combined with other variables, like clogged air filter, injectors, and tired fuel pump. which is very possible for the age.
but it's just my opinion, so pay no attention to it.
hmmm... a can of Seafoam through the fuel tank and run for half an hour on the freeway to "clean the guts"? won't hurt anything. will clean much.
 
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Old 04-25-08, 01:17 PM
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somehow i do not feel that the difference should be great enough to cause that much of a trouble.


i diagnosed a cadillac one time that wouldn't start because the coolant temp sensor was out of range...the ecm was being told 150 F...it was about 40 F outside. the coolant temp sensor is, as i stated, a primary input and has a HUGE influence on fuel delivery.

the fact that the car falls on it face until warmed up sounds alot more like fuel delivery than a simple idle control issue...
 
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Old 04-25-08, 02:24 PM
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Originally Posted by carguyinva View Post
somehow i do not feel that the difference should be great enough to cause that much of a trouble.


i diagnosed a cadillac one time that wouldn't start because the coolant temp sensor was out of range...the ecm was being told 150 F...it was about 40 F outside. the coolant temp sensor is, as i stated, a primary input and has a HUGE influence on fuel delivery.

the fact that the car falls on it face until warmed up sounds alot more like fuel delivery than a simple idle control issue...
it is plausible. as a matter of fact, temp sensor is listed online, amongst other culprits, on several sites, as a possible reason for inability to start/maintaine idle on cold engine. it is always the last on the list either.
i am simply speaking from my personal experience. 1. the infamous 87 taurus, that had EXACTLY the same symptoms, untill i replaced ISCU. 2. i have total of some 20 yrs of repairing cars myself. 14 here in the usa, rest of them - back in ussr, and that was invaluable experience.
usually, when you enter the country as an immigrant, you start with cheap, beat up cars and slowly build it up. plus, you live in community where all are the same - old, cheap, always breaking down cars, and you fix them yourselves. my cars, friends cars, their friends cars, all kinds of issues, all fixed in the street corner. so, out of all this, i have yet to come across a car that will not start or will not maintaine idle due to coolant temp sensor.
this is why i do not feel like it. it is possible, i understand why, just not number one on my book. ISCU, vacuum leak, pinhole air leak that goes away as engine warms up and gaps close, clogged filters, resulting in poor fuel/air supply, choking cold engine, poor spark, burnt distributor contacts, weak ignition coil, bad wires, battery, alternator - that's the "usual suspects". this is what i have seen, and this is where my mind wonders to firstly. i guess, can't teach an old horse a new trick.
but what i have learned out of all those piles of automotive issues we dug through was that always look for the simpliest. most obvious reason first. unless you have a yugo or moskvitch, but then you have only 2 sensors to deal with and no electronics. if they work.
so, if the car runs fine on warm, and temp gauge is working fine, and it is not overheating - somehow i do not feel like it's temp sensor. or he would have had some temp related issues, even with 2 seperate sensors, like some of them do. just an opinion.
 
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Old 04-25-08, 07:33 PM
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the temp input carguy is talking about usually only talks to the cpu, not to guage.
temp is usually the cause with these symptoms.
Life begins when the kids leave home and the dog dies
 
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Old 04-25-08, 08:42 PM
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I must agree with ECT input out of range.....


Just finished a Volkswagon Motor Job that wouldnt start. Starved for fuel on the first start of the day....Ran fine for hours, cooled off and wouldnt start. Replaced coolant temp sensor...Fixed it.....

GM works --Unplugged is cold....shorted is hot......Unplug the sensor and run the car for a few minutes....If the symptom is corrected... Suspect ECT sensor.

Related to egr.... Im not sure if your year still uses one....But a failed thermal vacuum switch would allow EGR function which should be disabled when the motor is cold, and would trip a DTC 32, when vacuum is detected at egr without command. If you still have the vacuum label on the strut tower, trace out the hoses...It'll only take a minute, and may put your mind at ease.
Also on the EGR solenoid is a Small "Filter" which may be removed and cleaned if necessary.
 
  #11  
Old 04-26-08, 11:34 AM
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Even the_tow_guy was fooled by a temp sensor once on the wrecker. I know, SHOCKING! We were convinced we had a dead coil or ignition module. Got a temp sensor code when we finally got around to checking. Oops.
 
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Old 04-26-08, 04:56 PM
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then temp sensor it is. though he does not have starting problem, engine starts but does not maintaine warm up idle, and that is different from non-start one. but that's ok.
here's my final thought on it. been pondering since the 1st post.
if temp sensor checks out fine, here's my idea: it's 20 yo car. it starts, but does not maintaine rpms untill it worms up. it runs perfect on hot and problem returns only when engine is back to cold-cold.
what happens when engine warms up? metal expends. thus, here's my thought: piston rings. they are gapping on cold, and there's not enough compression in cylinders to maintaine rpms or, like he describes - even take off. unless he really steps on it. as engine warms up, rings expend, mait with cylinder walls, and compression goes up, restoring power and maintaining idle/rpms.
i have cure for that, but'll keep my yapper shut, until that temp sensor is proven at fault, or else.
 
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Old 04-27-08, 12:43 PM
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Originally Posted by carguyinva View Post
. the other thing i would check is the throttle blade for deposit buildup.
Could you explain what that causes exactly? Just curious myself. I hear this mentioned alot. But I don't get the theory of why something on a plate would do anything, rather than say if an orifice were blocked by carbon.
 
  #14  
Old 04-27-08, 05:57 PM
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it is the minute clearance between the outter edge of the throttle valve (blade) and the inside of the throttle bore that gives the engine its "minimum air rate". when deposits form on the edge esp, the amount of air that can get by the throttle blade is lowered, which over time will affect idle speed and stability. it can also cause throttle sticking.

servicing is very manufacturer specific as some say clean it if there is buildup, while others say do not clean. the "do not" clean group for the most part has put a coating on the throttle blade and/or bore to minimize deposit formation and the use of solvents may remove the coating, or worse, may wash into the shaft area and cause throttle sticking...in the open position!

i serviced an older buick one time that had the worst deposits i've ever seen...probably a quarter inch thick on the back of the blade. the car had some serious sag, stumble, hestitation and chuggle type driveability problems. i wouldn't have believed that a throttle body cleaning would have cleared it all up except that i worked on it...so i know it did.

manufacturers handle it nowadays electronically as far as compensating for change in speed...it's called adaptive learning. as for a sticky throttle, that's a mechanical issue and the only fix i know of is to clean it...
 
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Old 04-28-08, 06:13 AM
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Thanks. Interesting. Did not realize air was actaully designed to go past that gap. One learns something new all the time.

I have been hearing enough lately about injectors plugged, and carbon lately to start adding these fuel cleaners to my gas tank now. One bottle I just bought (by a nationally reknowned company) says it does it in one tankful. Their highly attractive bottle also sold me on it.
 
  #16  
Old 04-28-08, 06:21 AM
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i guess their marketing is working...

fuel additives are mostly not necessary...but if someone must try them, they should do so very sparingly...never more than the recommended amount to a full fuel tank and maybe only once or twice a year. gasoline quality has never been better in this country (i know...hard for some of you to buy that one) but it's true. the testing is rigorous and todays sophisticated fuel systems are very sensitive to change...just ask SLJ. i'm certain he can add to my claims...
 
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Old 04-28-08, 08:00 AM
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fuel additives are mostly not necessary...but if someone must try them, they should do so very sparingly
The problem with 'in Tank" additives is they will do very little for the Gummed up and carboned throttle blades. On a carburetor, or early TBI injection, Where the Fuel is mixed with air "Externally" and then ingested, The Modern "Port" injection systems spray fuel directly at the valve while the airflow is traveling into the cylinder. This "Cleaning agent Enhanced " fuel never actually passes thru the throttle blades.

The problem is referred to as "Coking" (Which I assume comes from the term for carbon Dust residue in refineries)
and is most commonly caused by a combination of Normal amounts of "Blo-By" from the combustion chambers thru the PCV , oil residue that can be vaporized thru the pcv or breather tubes, Normal egr function, and even poor air quality.

If the Injectors themselves are Clogging or restricted, then yes, an intank additive may help, provided it is used according to instructions, but it will prove virtually useless for the far more common "Throttle body GUNK".
 
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Old 04-28-08, 08:17 AM
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very true...and i'd also add that they can attack the coating on the inside of some fuel tanks. that's a bad day when that happens...
 
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Old 04-28-08, 08:31 AM
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Question Result of Temp sensor

WOW! A great deal of attention here! I love it, also gives me a chuckle. I do thank all of you for the attention though. I have replaced the temp sensor; which was located on the throttle rubber snorkel. I had to splice an adapter so the plug would work though. The car starts great; after about 1 minute of high idle I left off the accelerator and it did not stall.... but, It did go through points of where it seemed it was going to stall, started for lack of words started to choke itself out? So, it's idling along and about every 20 seconds it goes through this missing choking I'm gonna stall idle for about 5-7 seconds. The car has new fuel injectors new throttle rubber snorkel, all of that is nice new black and shiny aluminum. So I did not pull the throttle housing apart to check the throttle. That entire section is new. It has a new Ignition module. It has new spark plugs, wires. Once the car completely warms up it stops doing the "I wanna choke and stall thing" and runs fine. Temp sensor does seem to allow the car to come to an I wanna choke and stall idle faster than before; but otherwise, it still has issues. Trying to go down the road before it is warm causes it to cough and sputter for about 5-10 seconds before it does take off... and it does take off; sets ya right back in the seat. That being said, whats next?
 

Last edited by dmhartley; 04-28-08 at 08:42 AM. Reason: spelling of course
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Old 04-28-08, 08:37 AM
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I just Re read thru these posts....Was the fuel filter ever replaced?
 
  #21  
Old 04-28-08, 08:46 AM
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let me call Dad and check... brb

No it was not checked, They inspected it the fuel was clean and pretty looking so, they told him not to change it...
 
  #22  
Old 04-28-08, 08:57 AM
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Dump the filter.....How long ago was all this work done?

Another thing that comes to mind is you had an Ignition module changed. Unburned gas and Catalytic converters dont like each other. Ignition failure can lead to a restricted catalyst, But definitely get rid of the filter before condemning anything else.
 
  #23  
Old 04-28-08, 09:31 AM
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very well, fuel filter is next on my list. This work was all completed within the last 6-8 months. My Dad basically gave up, his mechanics gave up; he said they didn't know what else to do. It may take me a few days to do the fuel filter. I will keep you posted though. Thanks everyone!
 
  #24  
Old 04-28-08, 09:52 AM
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you did actually replace the coolant temp sensor right, not the air temp sensor thats usually in the rubber intake hose.
would suggest you unplug the vacum line from the egr valve and test drive it for a couple of cold starts to make sure its not related to the egr vac solenoid as mentioned by someone else if the egr valve opens on a cold engine its not going to run very good and hesitation or stall on acceleratiuon but once it warms up will not be noticable.
 
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Old 04-28-08, 01:36 PM
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Agreed....

Find the vacuum diagram...I believe it should either be on the radiator support, or the right hand strut tower.....

Suck down a pot of coffee, clear your brain, and look at the picture.......If I remember correctly, the egr and solenoid should be in the center of the intake manifold, on the 'firewaLL side' of the engine. It seems very intimidating, but check ALL the vacuum lines carefully, they are plastic "Tubes" and can be broken, burnt or melted very easily.

Replacing a fuel filter is easy enough for DIY, and wont be wasted, so by all means replace it if you are unsure how long it has been there.

SPEND YOUR TIME CHECKING , AND YOUR MONEY FIXING.

The key to saving money is to spend your time instead.
 
  #26  
Old 04-29-08, 08:14 AM
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I am willing to bet it was an air temp sensor due to its location. At the parts store I asked for a coolant temp sensor and thats what they gave me. I will investigate. I will also check the egr by unplugging as suggested. I will ingest a pot of coffee and find the diagram and check my hoses. I really appreciate everyones input here. Thank you very much. I teach High school so my time is limited as well as my funds; but I will work as quickly as possible and keep you notified.
 
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