MAF Sensor (ECM Code 34) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-04-2002, 05:09 AM   #1
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Default MAF Sensor (ECM Code 34)

First of all, this is a wonderful forum! I own a '90 SSE (one owner) and recently bought a '95 for my wife, so it was great to find answers to various technical questions I had, new & old. Further, I have to say that some of our high-brow friends with their Passat'* and Outback'* initially looked down on our new purchase--- then I pointed-out to them that our '95 get'* better mileage, has more power, is safer, handles great, it'* comfortable/roomy, and all at 1/2 or less in cost. All of you know this already, but the Bonneville'* are an awesome ride...!

Anyway, my '90 SSE'* "Checks Engine" light has been coming on and it is stalling at stop lights. I ran the ECM tester and it came up with a 'code 34' . So, does this mean that my MAF Sensor needs to be replaced or could it be this and/or other things wrong?

I am mechanically capable, but can not afford big bucks to have a dealer trouble-shoot this for me... Any suggestions?
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Old 11-04-2002, 11:11 AM   #2
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With those miles, I'd be real tempted to pull the TB and clean the whole thing, then replace the MAF sensor. There'* been some talk about even newer models with carbon buildup in the TB. You might even see a significant boost in performance as well. Hand in hand with the MAF is the O2 sensor. If you've owned the vehicle since new, you will know if it'* ever been done. They typically last about 60k. Do NOT use bosch parts. Get the stock AC Delco parts. Bosch is bad news. Most of our cars hate the plugs, and the O2'* are worse.

Welcome to the Forum, Rev!
Good to have a couple more bonnevilles here!
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Old 11-04-2002, 12:44 PM   #3
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The Bonneville.

We all love them and they are a great car, but be very careful with the consistent inconsistencies. Its like trying to measure in a crooked room there is no edge to use as a base.

So first make sure you get acquainted with all your plug wires and plugs. Then go to an AutoZone and get your battery and alternator tested. Once you have done this make sure you look into your DIS system. The three little coils that distribute the spark to your sparkplugs. Always check the easy stuff first then get dirty. Take it slow and most of the time if you measure 4 times and cut once with the Bonneville you will be ok. Bill is right though and the MAF sensor could be ready for a replacement.

Welcome Jim.

Ty
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Old 11-04-2002, 03:04 PM   #4
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Interesting stuff!

A little background on my '90 SSE: This problem seems to have started last winter when I noiticed it not starting on the first crank a few times (it has started flawlessly for 12 years). However, it always fired on the 2nd try on the occasions when this happenned. So, if these incidents are related, it seems to be a gradual thing (carbon build-up?). Also, I replaced the O2 sensor (Bosch!) this summer, bypassed the A/C pump when the compressor went-out (in Colorado, I can live without A/C), and we have gone through 3 alternators in 18 months (all warranteed; our only consistent problem with the '90 SSE; this time I got the good one).

We have 6" of snow and my garage is filled with another project (straight carbaration & spark--- something I know about). So, I am naively hoping to find the quick-fix: presently checking for shorts & will replace the O2. I will keep you posted, but I am curious if my cruise-control suddenly going-out (not a fuse) might support willwren'* theory of carbon build-up?

Regardless, I will employ your suggestions and let you know what I discover. BTW: After 12 years of ownership, I have a few useful posts for the forum relating to the Bonneville; more later. Thanks much!
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Old 11-05-2002, 12:51 AM   #5
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Ok Guy'*, I replaced the O2, the intake air temperature sensor (because it has never been replaced), checked for shorts (none), and cleaned the throttle body intake (STP only, but did not remove from vehicle and thoroughly clean).

I took the quick-n-easy approach and though it ran like a champ when I raced around (+30 miles) and seems to idle better, the 'Service Engine Soon' light is still coming on at idle. However, this only happens intermitently --- after 5-10 minutes at idle, the rpm'* tend to drop while at a stop light or while in Park, then pick back-up again, and then it ussually dies. Still, it may be significant to emphasize that at +2000 rpm it runs great and the SES light only comes on occasionally and never while cruising...

So, although it idles fine 80% of the time (SES light off), there is something that still is not right (SES light comes on, then the rpm'* stumble and/or the engine dies).

Questions:
1) Should I go ahead and invest in the MAF Sensor (A/C Delco)?
2) Regardless of the MAF, should I still remove and clean the throttle body first?
3) From what you have heard from me (and my abilities/approach), should I bite-the-
bullet and just bring it to the shop and pay the $$$ to them, or should I go for it
myself?

Thanks again! BTW: jr's3800, I live in Ft. Collins (Northern Colorado)
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Old 11-05-2002, 03:25 AM   #6
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I forgot to mention that, regardless of your excellent advice, I take full responsibility for any fix that I ultimately decide on. This '90 SSE has been great, but I appreciate that it has 191k miles on it and there is a point where big-ticket items inevitably start to fail.

I don't give up easy, so I will probably take my chances and go for the purchase of a new MAF and/or a scan tool. I am hooked on the newer Bonneville series, so a scan tool will be useful either way (I also own a '95). I will let you know how it all turns-out.

In the meantime, if any of you have any other tips, bring it on...
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Old 11-05-2002, 03:58 AM   #7
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If you do plan on getting rid of you 90 SSE, want to sell some exhaust manifolds, heads, intake and maybe some other parts in the name of ADTR research? In death I see new light, you should rebuild it better, stronger, faster, more comfortable. But it never hurts to ask.

-Hector
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