Car running to lean? Possibly Mass Air Flow Sensor?

Lesabre T-type or other H-body related topics.

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Car running to lean? Possibly Mass Air Flow Sensor?

Postby CrpseGrm on Thu Jun 16, 2005 5:19 pm

I recently bought an 87 lesabre with 66K miles on it. The car runs excellent with one exception. When it idles for more then 3 minutes the idle gets a little rough and the check engine light comes on. However, as soon as you give it gas the light goes away and the car runs fine. The guy I bought it from said his mechanic told him that the car begins to run lean after idleing for a few minutes and it's possilbly the mass air flow sensor. Does this sound correct? A new mass air flow sensor is only 70 bucks from autozone but I just want to make sure that's the problem before swapping it out. Could it simply be the spark plugs or something else? Thanks!
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Postby T on Thu Jun 16, 2005 8:55 pm

The MAF is not used at idle. Don't replace it unless you get a code. Have you tried pulling codes yet?
-T

'87 Lesabre T-type
L67 swap, CAI, STB, 180deg stat, Walbro 307 fuel pump, tranny cooler, Michelin XGT H4s, ZZP 3.4 MPS, AC 41-601 plugs.
PB: 14.447@95.08 (2.299 60ft.)

'88 Lesabre T-type
RIP

'98 Regal LS
296,000 miles

For questions concerning Lesabret.com, please e-mail me at lesabret@gmail.com
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Postby CrpseGrm on Fri Jun 17, 2005 12:10 am

The gentleman I bought it from said that the code they pulled said it was running lean, but it would only throw a cel after idleing for a minute or two, not while driving. He claims it's nothing that would hurt the car and it's only annoying, although the car did stall on me today while idleing in stop and go traffic. What would I need to pull the code from the car myself, or is there somewhere I could go that would do it for free? Could it be something as simple as the spark plugs or clogged air filter? I havn't really had the chance to take an in depth look at the motor yet but what would be good to look for that might clue me in? If it's hard to tell without the code I can try to pull it soon and see. Any help you can give me would be greatly appreciated, this is my daily driver and I want to make sure it's in excellent running condition.
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Postby T on Fri Jun 17, 2005 1:32 am

You can look <a href="http://lesabret.com/phpBB/viewtopic.php?t=1201">HERE</a> for instructions on how to pull codes. I can post a full diagnostic sheet for the correct code if you tell me what it is.
-T

'87 Lesabre T-type
L67 swap, CAI, STB, 180deg stat, Walbro 307 fuel pump, tranny cooler, Michelin XGT H4s, ZZP 3.4 MPS, AC 41-601 plugs.
PB: 14.447@95.08 (2.299 60ft.)

'88 Lesabre T-type
RIP

'98 Regal LS
296,000 miles

For questions concerning Lesabret.com, please e-mail me at lesabret@gmail.com
T
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Postby 2seater on Fri Jun 17, 2005 2:40 am

One thing that can do that is the O2 sensor goes dead after an extended idle, particularly if the car runs rich. Idle speed allows the sensor to cool below the temperature where it is active (600 deg. or so). Most manuals will mention the engine speed should be increased to 1500-2000 rpm for 30 seconds or so if idling is involved in doing any diagnostics to keep the sensor hot. If it hasn't been changed in a long time, it won't do any harm to do so and may help mileage as well.
Hal twoseater@tds.net 1990 Buick Reatta, turbocharged, Dynomax s/s UltraFlow, hand made turbo manifolds, ceramic coated, 160* t'stat, GM Tuners chip, larger throttle body, relocated MAF, 30# injectors.
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Postby CrpseGrm on Fri Jun 17, 2005 5:04 pm

Thanky ou very much for the link on how to pull the codes, it was very helpful. Using a paper clip worked just fine too!

I just pulled the codes and I got 2 different codes. A 32 and a 44. According to your link 32 says to check vacuum hoses and connections for leaks and restrictions and to also replace the EGR soleniod or valve. At a quick glance there doesn't appear to be any leaks or loose connections, could the EGR valve cause these symptoms? The other code 44 says the exhaust is lean and to check the ECM wiring and check for loose hoses and a leaking intake manifold. With those two codes being displayed does that point to anything more specific? What would you suggest I look at first?

Also, should I be worried about the lean exhaust condition? I used to have a turbocharged vehicle and running lean was very dangerous to the motor. Is this also true with this motor?

Lastly I read a couple posts about cleaning the MAF. Would a dirty MAF cause these conditions? It seems like a good idea to clean it anyway. Any more help you can give me would be greatly appreciated. Obviously I'm new to this board but so far it has been a great resource for information and the community has been very helpful so far. Thanks guys! :D
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Postby T on Fri Jun 17, 2005 6:09 pm

http://lesabret.com/phpBB/viewtopic.php?t=2299

http://lesabret.com/phpBB/viewtopic.php?t=384

Check out these two links for throttle body and MAF cleaning. If you clean the TB, change the oil afterward.

I will post the diagnostic procedure for those codes soon. A bad vacuum line going to the EGR would be a good explaination for both codes. A vacuum leak can cause a lean condition.
-T

'87 Lesabre T-type
L67 swap, CAI, STB, 180deg stat, Walbro 307 fuel pump, tranny cooler, Michelin XGT H4s, ZZP 3.4 MPS, AC 41-601 plugs.
PB: 14.447@95.08 (2.299 60ft.)

'88 Lesabre T-type
RIP

'98 Regal LS
296,000 miles

For questions concerning Lesabret.com, please e-mail me at lesabret@gmail.com
T
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Postby CrpseGrm on Fri Jun 17, 2005 7:34 pm

I will definitly do the procedures in those articles even if they are not related to the idleing problem. They look like a good cheap maintenance idea. If it is related to the EGR in any way, what would be a good cleaning agent to use on the EGR vavle in the event that it's stuck or opening/closing to slowly? Would CARB cleaner be safe? Thanks!
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Postby Mistascott on Mon Jun 20, 2005 5:47 am

Fix the EGR first -- there could be an air leak there from a bad solenoid or stuck valve that is causing you to lean out and stall (too much air, injectors can't compensate at full pulsewidth).

EGR diagnosis -- solenoid or valve usually but go to the link for a systematic way to diagnose. You can substitute your mouth for a vacuum pump (a la Full Metal Jacket).


See http://www.syty.org/old/d&e-code32.html and good luck.

as for the MAF, it IS used at idle (sends a gps reading to the ECM which adjusts fuel accordingly) and can cause codes and lean conditions (don't ask me how I know). :D
Scott
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87 LeSabre T-Type
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Postby CrpseGrm on Mon Jun 20, 2005 12:37 pm

Mistascott, thanks for the reply. I was just about to ask about the vacuum for the EGR system. I cleaned the MAF and the throttle body looked almost brand new so the EGR is my next step. I have a couple questions though. Is it more common for the EGR valve to go or the soleniod? If the EGR valve is stuck or slow is it possible to just clean it up a little bit with some carb cleaner so that it moves freely again? Also, how do you remove the EGR vlave? I know that last one might sound stupid but on my 87 the valve sits right in the top center of the engine and it looks as though it's attached with one nut towards the firewall side of the engine. That nut, however, looks almost impossible to get to with a wrench to loosen up, not to metion it's very rusty so it may take a little elbow grease. Is there something I'm missing, an easier way to get the EGR valve off?

I'm sorry for all the jumbled up questions, I'm just on a very tight budget and do not want to spend money on a new valve if it's not the valve at all. Thanks guys!
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Location: Mechanicsburg, PA

Postby T on Mon Jun 20, 2005 3:21 pm

The EGR can stick. Use a throttle body cleaner to clean it out, it works great on carbon.
-T

'87 Lesabre T-type
L67 swap, CAI, STB, 180deg stat, Walbro 307 fuel pump, tranny cooler, Michelin XGT H4s, ZZP 3.4 MPS, AC 41-601 plugs.
PB: 14.447@95.08 (2.299 60ft.)

'88 Lesabre T-type
RIP

'98 Regal LS
296,000 miles

For questions concerning Lesabret.com, please e-mail me at lesabret@gmail.com
T
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Postby Mistascott on Mon Jun 20, 2005 8:33 pm

Slick: Yes, the EGR bolt is a PITA to get to. That's why I'd recommend being sure of the cause of the problem before doing anything. Bottom line: http://www.syty.org/old/d&e-code32.html can save you $60 and a hell of a bolt headache.

A few months ago, I had a code 32 and stalling so I followed the flow chart and narrowed the problem down to the solenoid, which was allowing exhaust gas back into the intake at idle, when it is only supposed to do so at >2,000 RPM.

An easy way to determine if the solenoid is your problem is unplug the ported vacuum line (the one that does NOT go to the EGR valve) from the solenoid and then plug both the solenoid nipple and the ported vac line. Then, see if the ECM throws the code at idle. Make sure you reset the codes (w/ paper clip) before doing it. A lot of times the mechanism (in the solenoid) that regulates gas flow to the EGR valve goes bad, allowing the gasses through at idle.

If I were a betting man, it sounds like a solenoid issue. Since you said it goes away after revving the motor (>2000 RPM), it is consistent with a stuck solenoid. Once RPMs go above 2K RPM, the car can handle the exhaust gases. At idle, the car isn't designed to handle them, hence the solenoid.
Scott
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Postby CrpseGrm on Sat Jun 25, 2005 4:58 pm

I just ordered a new EGR vacuum solenoid, it should arrive in a couple days. Hopefully this fixes the problem. The EGR valve itself seems to work properly, I applied vacuum to it with my mouth and it moves freely. I did notice today while I was in line at McDonalds that when the engine hesitates or stutters during idle I can hear a clicking sound from the engine each time the engine stutters. Would this be related to the EGR system or does that clue anybody in on different issue? I really hope this solenoid fixes the problem, if not maybe someone else has some other ideas of what to look in to.
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Postby CrpseGrm on Tue Jun 28, 2005 1:19 pm

Sorry to keep rambling on in this thread but I don't think the EGR solenoid is my issue anymore. I blocked the ported vacuum line that goes to the solenoid and blocked the port on the solenoid and I still got the code 32 and 44. Also, I looked at the EGR valve itself while the rough idleing was happening and it does not appear to be opening at all during idle. I also plugged the nipple directly on the EGR valve to make sure it was not opening and still had rough idle. Can anyone shed some more light on this issue? I'm starting to love this car but I have to sit in about 30 minutes of stop and go traffic each day after working and it really sucks that the car keeps stalling on me.

*Edit*: I was just reading down through some threads and saw one post that said that if you disconnect the vacuum line from the solenoid to the valve that there should be no vacuum though the solenoid at idle. Well there is definitly vacuum though my solenoid at idle. However, this doesn't explain why I still have rough idle with the EGR valve plugged and not open at all. Please help!
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My trip/possible brake repair waiting for me at home

Postby Nathaniel Gjr. on Wed Jun 29, 2005 6:32 am

Hey everyone. my vacation her ei flroida has been relaxing. i did not go to as many places i would haveliked to becasue i have no car. i did not even get ot see aggies rides yet becasuei have no car and i had some family business to see to. i hope i can at least stop by for a few minutes one day this week before i leave saturday morning.
i did my mass airflow cleaning trick for my sistes regal gs and that car really runs smooth. i went against my wishes to fix her car becasue i was so upset at how she just was letting it fall apart and not doing the improtant maintanance and how she and my mo were liek " its old she should just get rid of it if she wants to.(ie and get a honda) :evil:

i called home and my mom told me my anti lock light was on. i got kinda mad because when i left the car was running great and the breaks were great too. they are brand new and the only repair i was looking at was my gimpy starter and headliner. i told her to start the car and let me know if the antilock light stays on tomorrow. thats going to suck getting back and having to possibly again not get my headliner for an unexpected repair. hopefully it is not anything. i will check with my scanner if i have any codes when i get back. all in all it has been relaxing. the first week the weather was crap though.antonio was not lying about the women down here. :) hot!!!!! hopefully my t will not be all messed up and be a pain in the *** when iget back. florida fun!!!!!!

Nat Gjr. :mtt:
Negative people are fuel for your positivity. 1989 Buick lesabre T-type Garnet Red Red,Black leather Interior, all power, repro rear spoiler,Pontiac Bonneville dual outlet exhaust muffler,new timing gears,kyb GR-2's. One of GM's last great cars. 1998 Buick regal GS sedan Green/Grey, supercharged.
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