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1989 Olds Delta 88 3.8L runs really bad...need help

My son has a 1989 Delta 88 3.8 L V6 140 Kmiles. Had problems getting it started. Adjusted the Throttle position sensor and it starts OK (with the MAP sensor unplugged). If MAP sensor is plugged in it will die (this is a replacement MAP sensor known to be good). Idles OK but on the road test it sputters and lopes (?) and almost wants to run right. Have to goose the accelerator pedal to pull away from a complete stop or else it will die.

A little history: Checked fuel pump and fuel filter OK. Changed the air intake temperature sensor a couple of months ago because it was way off temperature. Checked the coolant temperature sensor OK (3.6 VDC at about 160 DegF). Changed the spark plugs and has new wires. Cleaned the carbon from intake manifold a while back - it may be carboned again - haven't checked recently. No sign of vacuum leak or head gasket problem.

The Haynes manual shows the MAP sensor has Gray, Green/Black and Black wires to it. My son's car has Pink/Black, Black/White and Yellow wires. The voltages are pink/black to Black/White 12.3 VDC (ignition on and while running). Yellow to Black/white if 5 VDC ignition on and pulsing when running (0.5VDC and 0.7VAC on my multimeter - I don't have a scope). The MAP sensor has the part #AFH50M-02A embossed on it.

Couldn't find the crank sensor to test it.

Should I recheck any of the above items? Any hints would be appreciated. Thanks.

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Lurker
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Reply to
David J and Lynne J Shepherd

appreciated.

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Lurker

Lurker wrote in alt.autos.gm

Do you get any codes on the computer? Recheck the plugs and see if any are fouled. snip.

Reply to
Dick C

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Lurker

I think this one is the same as my '84 3.8 with a different MAF setup. You should check/change the dist. cap rotor and coil pack as these are cheap, and you probably don't have a scope to check them properly. If that doesen't do it, (which I am guessing it won't) check the cam timing in relation to the crank. I am guessing the timing chain/belt/whatever has slipped. Since the MAP/MAF is known good, when it is unplugged the engine goes to the factory preset where the timing is retarded, when it's plugged in the timing is advanced to the normal place, which puts it too far out and the engine dies.

But, if that checks OK, then you need to review the MAF/MAP again. (I assume this is the MAF not the MAP and your post just labeled it wrong) How do you know it's good? I can tell you this on my 84, the engine ran rough due to a failed MAF. I diagnosed it and replaced the MAF with a rebuilt one, and it still ran like crap. I gave up and took it to a professional mechanic and HE diagnosed the same damn thing by substituting with a good MAF he had on the bench. I told him to get a rebuild replacement (new ones are $300+ on that engine) and he went through TWO rebuilds before the 3rd one he got was good. I don't know what problem it is that the rebuilders have with these devices but they apparently do. Needless to say I was rather pissed off at the place that sold me the first rebuillt MAF.

Ted

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Ted Mittelstaedt

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Lurker

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