problem with air flow sensor?
10-10-2010, 04:57 PM
#1
Instructor
Thread Starter
problem with air flow sensor?
I have a 1987 951, and it has no power. Zip, nada, none. I really seems like the air mixture is off, as the compression test on it was good.
Is there any chance that the barn door in the air flow sensor (is that what this is called) is not opening? How much pressure does it take to move that door (I've had it out, and could move it, but it seemed pretty stiff to me).
I need to do the timing belt, coolant, water pump, thermostat, etc. I just don't want to go ahead and get that all done only to find out that there's something serious with the engine. I'm sure there are Chevettes (yes, Chevettes, not Corvettes) out there that are faster than this car right now.
Is there some way to check this sensor?
Is there any chance that the barn door in the air flow sensor (is that what this is called) is not opening? How much pressure does it take to move that door (I've had it out, and could move it, but it seemed pretty stiff to me).
I need to do the timing belt, coolant, water pump, thermostat, etc. I just don't want to go ahead and get that all done only to find out that there's something serious with the engine. I'm sure there are Chevettes (yes, Chevettes, not Corvettes) out there that are faster than this car right now.
Is there some way to check this sensor?
10-10-2010, 05:17 PM
#3
Instructor
Thread Starter
Thanks for replying Doug. The intercooler tubes look good, but I'm not making any boost. The gauge rises to 1 bar only, no more.
Some people have suggested that maybe the turbo is not working, but I cannot believe that a car with a bad turbo would be this slow. I would assume that there would be some good acceleration, like a normal 4 cylinder, rather than this. The only thing I can compare it to is my wife's Jetta TDI with a MAF sensor problem. Unplugging the sensor on my car causes it to run rough, so I know it is at least doing some good.
Some people have suggested that maybe the turbo is not working, but I cannot believe that a car with a bad turbo would be this slow. I would assume that there would be some good acceleration, like a normal 4 cylinder, rather than this. The only thing I can compare it to is my wife's Jetta TDI with a MAF sensor problem. Unplugging the sensor on my car causes it to run rough, so I know it is at least doing some good.
10-11-2010, 02:50 AM
#5
Rennlist Member
your car doesn't use the maf until it goes of idle anyway but noticing it change when unplugging should mean it's functioning. Go onto clarks-garage and check the testing procedures for the AFM, should be able just to use a multimeter...if your not getting boost at all then I would look at the all vac lines, intercooler piping/hoses, BOV, Cycle Valve, Wastegate,and Turbo. Generally in that order since that would be the cheapest route.
But test your sensors first, AFM and TPS should be the main ones.
But test your sensors first, AFM and TPS should be the main ones.
10-11-2010, 02:51 AM
#6
Rennlist Member
Any hoses with cracks as you know should be replaced, if it's a wastegate and your on a budget talk to teamcrossworks he sells rebuilt 15psi units... I have one best 200 I've spent yet.
10-11-2010, 02:59 AM
#7
Burning Brakes
There's a procedure on clarks-garage to check AFM, although my car has been MAF'ed since before I could drive, so I don't have any experience with AFM.
Could you be any more descriptive on the issue? It sounds like it starts and runs but just won't go into boost? At all? Does it stumble around? And does it idle? Stuff like that would be helpful.
If it runs but won't go into boost, I'd look into cracked IC, hard pipes, j boot, exhaust manifold or possibly a vacuum leak.
Could you be any more descriptive on the issue? It sounds like it starts and runs but just won't go into boost? At all? Does it stumble around? And does it idle? Stuff like that would be helpful.
If it runs but won't go into boost, I'd look into cracked IC, hard pipes, j boot, exhaust manifold or possibly a vacuum leak.
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10-11-2010, 03:10 AM
#9
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10-11-2010, 02:35 PM
#11
Instructor
Thread Starter
Probably not...I'd just be surprised that that's what's causing it.
Guess I'll start pulling things apart to look around and see what I can find. Wish my other project in the garage was complete now...
10-11-2010, 02:53 PM
#12
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+1 on clarks garage. Before tearing anything apart, use one of the small, plastic clamps from home depot to clamp the WG line. Ease into the throttle and see if "boost gone wild" occurs. This will take 2 minutes and no disassembly....
What was the onset of this? All at once?
What was the onset of this? All at once?
10-11-2010, 03:03 PM
#14
Instructor
Thread Starter
It was like this when I bought it.....unloved and unmaintained. And yes, it does bog down under WOT, but then again, it's not as bad once it heats up.
A sign og something specific?
A sign og something specific?
10-11-2010, 04:04 PM
#15
Instructor
Thread Starter
Can someone actually post a picture for me of the wastegate line that I should be clamping? I've tried looking around for it, and for the life of me I cannot find it referenced anywhere in the manual.