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Category: Chevy
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1987 chevy astro: v6..the floor and crank..starts right..running rough

Customer Question

I have a 1987 chevy astro van v6. At times the only way it will start is to keep the gas peddal on the floor and crank for a while and it will finally start, but run rough, back fireing, and die when put into gear. Other times it starts right up, runs for a while then the idle starts to speed up , and then goes in the same mode of running rough and backfiring until dieing.   It will start back up again when it cools down, but repears the above. Then sometimes it runs??? Any help out there?
Submitted: 9 years ago.
Category: Chevy
Expert:  Triston replied 9 years ago.
do you get any color smoke?
Customer: replied 9 years ago.
Not really. No excess black or white smoke. When it starts to act up the rpm increase like its leaning out and then it goes to it's runing rough ann backfireing mode when I throttle it.
Expert:  Triston replied 9 years ago.
it' will be back inabout 30 minutes.
Expert:  Triston replied 9 years ago.

ok 1st disconnect the sensor on the picture below, if it now start and run with out it, replace it(MAP sensor). remove some spark plug to see if they are gas fouled, if so replace the plugs and fuel pressure regulator. to check for a weak cylinder, dis able the ignition, when you crank the engine it should sound even, if not suspect valve train and have a compression test done. to eliminate the exhaust remove the EGR valve pipe or the oxygen sensor and see if the truck now runs. check the timing and the fuel pressure (spec.9 to 15 psi) if lower replace the pump if higher replace the regulator. also make sure the throttle plate are opening properly. make sure the spark plugs wires are routed correctly. good luck. i hope i helped and please accept if satisfied. thanks T-MAN


Click image to see an enlarged viewFig. 1: Common GM style MAP sensor

The Manifold Absolute Pressure (MAP) sensor measures the changes in intake manifold pressure, which result from the engine load and speed changes, and converts this to a voltage output


Customer: replied 9 years ago.
Hi Triston,

Ok, so I tried pretty much everything you suggest. The spark plugs were wet and this is what I notice. When first starting things are cool , runs good untill it heats up. At that time the throttle body really starts hissing, the engine starts running very rough, Smoke is coming out the exaust. It get rougher and rougher, over a period of 2 to 4 minuites, to the point that it's impossable to keep running and will not restart. Let it cool down and the cycle starts over again. Hopefully this helps.

Aloha, Rob...