1992 gmc 1500 with an 89 1500 motor and trans. will idle but soon as in rev or drv it falls on its face! Help!!!


Asked by Dec 01, 2013 at 10:35 PM about the 1992 GMC Sierra 1500

Question type: Maintenance & Repair

hello all i swapped the motor and trans outta my 92 1500 with an 89 1500. only changes were to the tbi cause of cruise control and iac connector. it will crank and idle fine with good response but soon as i put in reverse or drive it starts running like crap and will stall out when given gas. is this a spark issue or fuel? low fuel pressure? any help is greatly appreciated!

2 Answers

believe the fuel pump relay is droppin' out intermittently when chassis ground is not altogether there~ "brown out power" is what is happening as the circuit cannot complete the necessary draw to keep the fuel pump relay engaged...is droppin' out intermittently.. and thats why you need to wirebrush the main ground connection to insure the 12.5 volts to all of the chassis devices~...test this power at the bus...at the coil...at any of the positive side fuses to discover a compromised voltage for was it bad ground~


thanks for the quick response. so i looked and noticed my main motor to chassis ground was loose. i wire brushed the metal and tightened it down but the truck is still doing the same thing. i also cleaned up all the other grounds and tightened them down.should i replace the map sensor or any other sensors with the ones off of my 92 motor? i drove it today and it ran fine going down the road for bout 30 seconds then stalled out and died. it will crank right back up but it was lacking power on the way back to the shop.. this has me stumped...

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