92 Lesabre Mass Airflow Problem

OptimistPrime

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Hello. This is my first post at this forum. I looked around but couldn't find anything relevant searching. I have a 1992 Lesabre. It was my Grandma's car when she was alive. I've had it for a few years now, running it fairly trouble free. It has less than 50k original miles on it. Practically like a new car. Then recently it developed an issue with the check engine light. I was getting laggy acceleration and sluggish starts, and my mechanic advised I replace the MAF. I purchased a brand new MAF from a reliable vendor online. The check engine light went away and the car seemed to drive flawlessly. For a couple of days, things were great.

Then the problems started again. First, I noticed extremely rough idling any time I started the car warm. Problems would remain until I drove it at speed or revved the engine hard. After that it would drive fine, albeit with a slightly rough idle. Then on a recent outing, the check engine light came on again.

This is a problem a lot of these cars have, so I began the process of troubleshooting the root of the issue. Unplugging the MAF lets the car drive fine, though the check engine light stays on. Perfect acceleration and no hesitation when I do this. This would seem to indicate a problem with the part I was sent, however I'm not entirely sure. Using a method I saw on Youtube, I used my multimeter to probe the MAF connector lines. My meter read no voltage going to the MAF, however I am wondering if I might have misread things. No voltage going to it at all would mean the check engine light would stay on even when the MAF is plugged in. At least I assume so. I don't know very much about cars, but I know when the one I drive daily isn't working right.

I'm open to suggestions on this. I'm considering returning the part, but if I do I want to be sure it's actually the issue.
 

OptimistPrime

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Thanks for your response. Yes, that is the method of testing that I used. I must need a set of those wire probes for my multi, because it gave off no volts at all. But, like you said, with no volts the thing just wouldn't be working. And it would have a constant check engine light like it does when I run it without the MAF.

This is the third MAF I've tried. The first two were from junkyard cars, so they were probably just bad to begin with. In both cases the junkyard MAFs worked for a couple days before fouling out and giving the check engine light. This new MAF is the first time I've noticed the rough idle condition. I drove it for a couple hundred miles with no problems but now it seems to be going out as well.
 

HotZ28

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What is the brand of new MAF? Are you sure the Air Intake Temp Sensor in place and functioning properly and has the air cleaner been checked, or replaced? I have never had much long term success with any MAF except ACDelco, Delphi, or Hitachi.
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OptimistPrime

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What is the brand of new MAF?

It doesn't really have a brand listed on it, which probably is a bad sign. The retailer is well known to me but not the manufacturer. I paid 60 bucks or so for it, which I understand is fairly cheap. It has a warranty so it looks like I'll just return it and get a name brand MAF. I really would prefer to have Delco in it anyway.

Are you sure the Air Intake Temp Sensor in place and functioning properly

Not sure. This interests me, because the vehicle drives great when it's cold. The rough idle doesn't occur until the car has been driven, then stopped and restarted, thus slightly warm. I guess it's another thing to test.

has the air cleaner been checked, or replaced?

It's got a new air filter. The air cleaner is in fairly good shape since this car is low mileage.

I have never had much long term success with any MAF except ACDelco, Delphi, or Hitachi.

This is what my mechanic was scolding me about. I didn't know but apparently getting a MAF sensor to work right is incredibly delicate and not suited to these knockoff brands.
 

fullmonte44

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I agree with hotz28-it could be the aftermarket brand. My "92 LeSabre had an AC delco original sensor that developed a crack in the case and made the engine run erratically-sometimes a poor idle, or a prolonged skip when driving. I tried some brand other than original equipment, it was used from a junk yard, it ran worse than with my old sensor. So next time I tried AC Delco-it was a used unit, too- but it works perfectly. Been working great for over a year now.
 

OptimistPrime

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Thank you for your responses. I tried to respond to thank you a couple of days ago but the post never went through. Not sure what's going on.
I was wondering if HotZ28 knew of a way to check that air intake temp sensor.
 

fullmonte44

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Thank you for your responses. I tried to respond to thank you a couple of days ago but the post never went through. Not sure what's going on.
I was wondering if HotZ28 knew of a way to check that air intake temp sensor.

I looked at my Haynes manual. Here it is: The sensor can be checked with an ohmmeter, by measuring the resistance when cold, then warming it up (can use a hairdryer) and taking another measurement. "If the difference in resistance is not approximately 500 ohms, the sensor is probably bad."

Did you determine if the MAF sensor is getting battery voltage on the pink/black wire? It has to be consistent. That wire comes from the 10 amp fuse #17
in the relay center, which is hot in run or start.

Here is something to keep in mind, in case anyone tells you to check your EGR valve. The '92 LeSabre 3.8L engine does not have an EGR valve, and did not come equipped with one from the factory. This much surprised me to find out-I thought all engines had EGR valves, couldn't figure out why mine wasn't there. But it is true, they did not include one on this engine-I finally ran across that statement somewhere.
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OptimistPrime

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I've been having trouble getting my multimeter to read on any of this car's sensors. It has to be a fault in my meter, because I've tried the IAT, MAF, TPS and even the rear wheel speed sensors, and nothing reads. These systems can't all be faulty. I'm working on finding someone with a multi that can actually do the job. In the meantime, I've tried replacing the IAT and running the car without it, and I couldn't tell any difference in the way it ran.

I removed the IAC, which I found to be quite dirty, and cleaned it off with some MAF cleaner. I also tried the car with the MAF plugged in but IAC unplugged, and found the rough idle condition resolved itself. The car was idling at a high RPM, but it ran smooth. After cleaning the IAC, I reinstalled it and found the car to run much better going down the road. The rough idle condition still persists, but to a much smaller degree.

At this point I'm thinking I may have a bad IAC. I cleaned out the inside of it real well, but I'm wondering if the throttle body might need to come off to be fully cleaned. Is just scrubbing the inside of the IAC hole with MAF cleaner and a little carb cleaner enough to suffice? To clean the IAC, I submerged the head in MAF cleaner and scrubbed it with a toothbrush. The fact that it's still having problems makes me think I should just go ahead and get another, since it's a fairly cheap part.
 
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