1990 with stalling/hesitation, pulled code 34 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-29-2012, 09:35 PM   #1
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Default 1990 with stalling/hesitation, pulled code 34

I have a 1990 Bonneville SE(?) that'* been developing a raft of electrical issues the past couple of years. Already had a shop replace a number of fuel control sensors and solenoids this past year after a particularly nasty bout of a car that would endlessly turn over but never fire, and now it seems another one is giving me fits.

48 hours or so ago, I started getting my SES light kicking on periodically, along with some hesitation in the engine, and now it'* stalling periodically both in gear and idle.

Did the OBD1 jumper diagnostic, received code 34.

A brief Google turned up that the code indicates a problem with the MAP sensor, but my knowledge of the problem begins and ends there.

Looking for some help puzzling out this issue, and perhaps some insight into whether my limited tool-set and rudimentary knowledge might be enough to solve this problem myself without a costly repair bill.

Am I simply buying a new solenoid or relay to patch in, which wires or harnesses should I examine, or where should I start? Of course, if beginning to solve this particular problem with my amateur knowledge is even remotely recommended. If any electrical systems tools are needed beyond a simple patch/splice or any fiddling with the ECS beyond replacing a part to spec, I wouldn't feel comfortable approaching this problem, unless it'* relatively straightforward.

The engine is stock-standard from the factory, barring whatever component needed replacing along the way.

Is there anyone who might be able to help me out? Thanks in advance.
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Old 04-30-2012, 06:06 AM   #2
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If you are getting a code for the MAF sensor, your hesitation/stalling is related to a bad or EXTREMELY dirty MAF sensor.

You can disconnect the MAF sensor and see how it idles and drives. If it improves, your MAF is the culprit.
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Old 04-30-2012, 06:12 PM   #3
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Thanks, I'll try that troubleshooting tip. A guy at work also recommended cleaning the sensor with Electronics/Brakes cleaner and re-installing it. Is disassembling the MAF and cleaning the interior of the cavity of the sensor mount ever recommended?

Had a massive sticker shock today over the price of a new MAF assembly. Hoping it won't come to that, the part alone is more than I was banking on for a total repair bill! Are there any resources where I might be able to obtain just the sensor module without an entire new mount? I haven't had much luck with that search, and a $300 price for the full assembly is outrageous!
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Old 04-30-2012, 07:29 PM   #4
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I've been buying most of my car parts from Rock Auto, they have a decent selection of parts. You should be able to get a MAF Sensor for under $200.
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Old 04-30-2012, 08:49 PM   #5
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Unplugged sensor, and car seemed to run idle and stayed steady when I upped the rpm slightly with no issue barring a slightly different sound to the motor. Plugged it back in, and the problems came back immediately. Tried some MAF cleaner I picked up to no avail. Otherwise, car'* running nominally, no strange sounds in the engine and it starts up with no issue.

Pretty good indications I need a new one?

Ended up finding one for $180, complete assembly. Has to be shipped in, so I have a couple days to figure out how to get it in.

Anything I need to be aware of before I put this part in? Is it as simple as it looks to swap out?
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Old 04-30-2012, 08:55 PM   #6
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Yea, when you disconnect the sensor, the PCM automatically reverts to a pre-determined table of values, usually based on RPM vs cylinder volume etc etc.

There is one more test, but more of a formality... test for 5V DC at the electrical connector for the MAF sensor. I'd hate to see you spend all that money when it was just the sensor not getting power.
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Old 04-30-2012, 11:12 PM   #7
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Thanks Got a multimeter at work I can test first thing tomorrow.
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Old 04-30-2012, 11:40 PM   #8
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also make sure that the ''filament'' in the sensor is completly surronded in plastic other than the pass thru the bottom should not be open.Ive pulled MANY out that left the small bottom peice in the TB
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Old 05-01-2012, 01:13 PM   #9
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@sseidriver97
Hmm mine must have come apart then, as the filaments were fully exposed. Intact, but there certainly wasn't any sort of cover over them.

@Mike1995 So I tested voltage at the connector, but I may have done it wrong so I will use this guide I found and try the three tests it lists once more at lunch.

I got a reading of 11.73v coming off the hot lead on the connector, is that acceptably close to the 12v target (seen elsewhere) for that lead?

I need to go out and test the ground connection, and I'm not even certain how I'll even be able to test the hertz coming off of the MAF signal, as the car won't even stay in idle long enough with the sensor connected to look at that.

Noticed as I tried to drive to work today that it was acting even worse, not even trying to accelerate, so I unhooked the sensor completely and got to work fine. Tries to rabbit for half a sec when I first touch the accelerator, but otherwise behaves unremarkably. Will it do any damage to the motor if I drive it that way short-term for commute? I have about a 5 mile commute I may have to make 1 or 2 more times before I receive my part.
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Old 05-01-2012, 08:09 PM   #10
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Maybe it was 12V DC... You will need a meter capable of measuring HZ if you wanted to check the output of the sensor. Otherwise, the simple check of unplugging it and driving it is a good enough test to indicate that it is faulty.

Shouldn't hurt too much, just your wallet at the pump and the parts counter.
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