Question about 1988 GMC C1500

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I have a 1988 5.7 gmc that after start up idles fine runs stromg under full throttle but at highway speed and under no load speed it sputters and at slow speed it is running rich i have done complete tune up rebuilt the tbi one concern i have is someone removed stock air cleaner system and the one they installed has no intake air sensor could this be the problem ? and also i have no codes and no ck engine light on

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Disconnect the EGR valve (hose) and see how it runs, sometimes the spring gets weak and it opens too much, or at idle it should not be open at all (solenoid leaking vac) The air temp sensor isnt in the air cleaner..

Posted on Jan 03, 2011

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I have a 1988 5.7 gmc that after start up idles fine runs strong under full throttle but at highway speed and under no load speed it sputters and at slow speed it is running rich i have done complete tune up rebuilt the tbi One concern i have is someone removed stock air cleaner system and the one they installed has no intake air sensor could this be the problem ?
IT CERTAINLY CAN BE THE PROBLEM. The air flow sensor if a VITAL part of your fuel delivery and emmision's system. Your mixture is controlled by a computer that uses the sensor data from that device. If you possibly can get the old one, put it back on. It is possible that I may not be totally right about this point but the operation of your engine is dependent on all the parts being there.
and also i have no codes and no ck engine light on.
There may not be code for a missing part. That system is not perfect.
I hope this helps,
Happy New Year,
Mark

Posted on Jan 03, 2011

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