Bad MAF?
Thread Starter
Instructor
Joined: Jul 2000
Posts: 203
Likes: 3
From: Galesburg IL
Bad MAF?
I have been fighting a problem with my '85 for a couple of years. It has gotten progressively worse. It has been throwing an intermittent code 33.
I could go for months without throwing the code and then it pops up again. After throwing the code the car barely runs. Leave it sit for a while and then it starts up and runs fine. This is starting to happen with more frequency. Also, idle is fine for a while and then becomes erratic and then is fine again. I have checked all of the connections, have made sure that connectors are seated properly, and checked for vacuum leaks. Just curious if anyone knows if a MAF sensor can go out slowly over time and go intermittent. Since the problem comes and goes rapidly, it has been hard to diagnose.
My '85 does not have burn-off relays, but rather the much more expensive burn-off module. I suppose that part could be a suspect as well.
Thanks in advance.
Steve
I could go for months without throwing the code and then it pops up again. After throwing the code the car barely runs. Leave it sit for a while and then it starts up and runs fine. This is starting to happen with more frequency. Also, idle is fine for a while and then becomes erratic and then is fine again. I have checked all of the connections, have made sure that connectors are seated properly, and checked for vacuum leaks. Just curious if anyone knows if a MAF sensor can go out slowly over time and go intermittent. Since the problem comes and goes rapidly, it has been hard to diagnose.
My '85 does not have burn-off relays, but rather the much more expensive burn-off module. I suppose that part could be a suspect as well.
Thanks in advance.
Steve
Last edited by steveb; Feb 10, 2009 at 08:45 AM.
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Have you done any diagnostics? Do you have the factory service manual? If you don't have the fsm, pm me and I will send you the diagnostic test procedure for the burnoff module and the MAF.
Maybe someone else who has their fsm at hand will chime in, mine's out in the garage. Do you have a digital voltmeter? Do you have the tools needed to replace any parts? If not then I suggest taking the car to someone who does.
Maybe someone else who has their fsm at hand will chime in, mine's out in the garage. Do you have a digital voltmeter? Do you have the tools needed to replace any parts? If not then I suggest taking the car to someone who does.
Thread Starter
Instructor
Joined: Jul 2000
Posts: 203
Likes: 3
From: Galesburg IL
Have you done any diagnostics? Do you have the factory service manual? If you don't have the fsm, pm me and I will send you the diagnostic test procedure for the burnoff module and the MAF.
Maybe someone else who has their fsm at hand will chime in, mine's out in the garage. Do you have a digital voltmeter? Do you have the tools needed to replace any parts? If not then I suggest taking the car to someone who does.
Maybe someone else who has their fsm at hand will chime in, mine's out in the garage. Do you have a digital voltmeter? Do you have the tools needed to replace any parts? If not then I suggest taking the car to someone who does.
Thanks,
Steve
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I am in possession of a Helms manual and have the necessary tools. The flow chart seemed to indicate an intermittent condition that could be caused by a wide variety of items including faulty ECM. The fact that the condition comes and goes so infrequently has me baffled. I will double check the diagnostics and see what I get. Just was wondering if a part like the MAF could possibly be going out slowly over time and be potentially causing problems.
Thanks,
Steve
Thanks,
Steve
Thread Starter
Instructor
Joined: Jul 2000
Posts: 203
Likes: 3
From: Galesburg IL
Get a can of MAF cleaner, it is a specific product. The next time it is acting up, spray the MAF real good, let it dry then start the car. If the problem is gone then I would drive it and see how long it takes to come back. If it comes back right away you can usually eliminate the burnoff module. If it runs good for a stretch of time then acts up again then the burnoff would be suspect. You can also use a screwdriver handle to tap on the MAF to see if the problem clears up. The diagnostic tests are great but they can only find the problem as it is happening. Good luck, cwyates and I both had a he11 of a time with almost the same problem, mine was the burnoff.
Steve
Advanced
Joined: Mar 2001
Posts: 89
Likes: 1
From: ca
Unplug the MAF the next time it acts up. The ECM will revert to a fixed default setting from it's memory. it should idle smoothly with those settings. This isn't a fix, it just eliminates the MAF and the burn-off as a source of the problem.
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
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From: Kempner Texas
I had a similar problem when I installed an out-of-the-box K&N air filter.
The red oil spray on the filter (factory applied) was migrating onto the MAF wires resulting in erroneous readings.
When I sprayed MAF cleaner on the MAF wires, things returned to normal.
If you choose to spray, I recommend you turn the MAF upside-down to prevent any liquid from entering the electronics of the MAF.
Jake
The red oil spray on the filter (factory applied) was migrating onto the MAF wires resulting in erroneous readings.
When I sprayed MAF cleaner on the MAF wires, things returned to normal.
If you choose to spray, I recommend you turn the MAF upside-down to prevent any liquid from entering the electronics of the MAF.
Jake
Pro
Joined: Nov 2005
Posts: 602
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From: North Bay Ontario
My '85 did exactly the same thing that you described ONCE last summer. It was running purr-fect the previous time that I was out with it. A couple of days later, the check engine light came on as I was backing out of the garage. Pulled out on the street, it had no power on acceleration, limped down the street, turned around while keeping one foot on the gas pedal and the other on the brake; got back in the driveway, shut it off and waited 10-15 seconds, fired it up, and it ran just the way it should - I think the check engine light went away too. I drove off, checked for a stored code later and got 33. Never had it happen again, but have always wondered...the only explanation that I could come up with, but I don't think it was the cause - I had vacuumed some drywall dust using the central vac which exhausts into the garage and thought it might have affected the burn off - but I doubt it. I'm curious as to what you find out, 'cause I figure I'm headed down the same path...
Thread Starter
Instructor
Joined: Jul 2000
Posts: 203
Likes: 3
From: Galesburg IL
Update:
The weather was finally nice and I had some time to rerun some diagnostics. Here is what I found.
Burnoff seems to be working. Looked to see if the wire glows after turning off the ignition. It does.
Ran through the code 33 flowchart in the service manual again. Everything checks out and leads me to checking all connector terminals for making good contact. If all are ok, service manual says it is a faulty MAF.
The connector going into the MAF appears to be fine except for the plastic locking tab that broke off. I am going to remove the windshield wiper motor and check the grounds this weekend if time permits. Last few startups have been fine with no 33. But I have a feeling it is going to do it again. Pletzvet, that is exactly how it started out with mine.
Are there any other connectors that I need to look at? I did spray the MAF with MAF cleaner. Will see if that has any effect. If I find out anything for sure, I will post the solution.
Thanks,
Steve
The weather was finally nice and I had some time to rerun some diagnostics. Here is what I found.
Burnoff seems to be working. Looked to see if the wire glows after turning off the ignition. It does.
Ran through the code 33 flowchart in the service manual again. Everything checks out and leads me to checking all connector terminals for making good contact. If all are ok, service manual says it is a faulty MAF.
The connector going into the MAF appears to be fine except for the plastic locking tab that broke off. I am going to remove the windshield wiper motor and check the grounds this weekend if time permits. Last few startups have been fine with no 33. But I have a feeling it is going to do it again. Pletzvet, that is exactly how it started out with mine.
Are there any other connectors that I need to look at? I did spray the MAF with MAF cleaner. Will see if that has any effect. If I find out anything for sure, I will post the solution.
Thanks,
Steve
Thread Starter
Instructor
Joined: Jul 2000
Posts: 203
Likes: 3
From: Galesburg IL
Update:
The weather was finally nice and I had some time to rerun some diagnostics. Here is what I found.
Burnoff seems to be working. Looked to see if the wire glows after turning off the ignition. It does.
Ran through the code 33 flowchart in the service manual again. Everything checks out and leads me to checking all connector terminals for making good contact. If all are ok, service manual says it is a faulty MAF.
The connector going into the MAF appears to be fine except for the plastic locking tab that broke off. I am going to remove the windshield wiper motor and check the grounds this weekend if time permits. Last few startups have been fine with no 33. But I have a feeling it is going to do it again. Pletzvet, that is exactly how it started out with mine.
Are there any other connectors that I need to look at? I did spray the MAF with MAF cleaner. Will see if that has any effect. If I find out anything for sure, I will post the solution.
Thanks,
Steve
The weather was finally nice and I had some time to rerun some diagnostics. Here is what I found.
Burnoff seems to be working. Looked to see if the wire glows after turning off the ignition. It does.
Ran through the code 33 flowchart in the service manual again. Everything checks out and leads me to checking all connector terminals for making good contact. If all are ok, service manual says it is a faulty MAF.
The connector going into the MAF appears to be fine except for the plastic locking tab that broke off. I am going to remove the windshield wiper motor and check the grounds this weekend if time permits. Last few startups have been fine with no 33. But I have a feeling it is going to do it again. Pletzvet, that is exactly how it started out with mine.
Are there any other connectors that I need to look at? I did spray the MAF with MAF cleaner. Will see if that has any effect. If I find out anything for sure, I will post the solution.
Thanks,
Steve
--sb--