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1997 Pontiac Grand Prix SE Issues

1997Madscientist

1997Madscientist

New member
I have a 1997 Pontiac Grand Prix SE that just had the upper engine wiring harness replaced after an underhood fire destroyed my fuse box. I got it running the other day and noticed a few issues. First, their is an obvious miss in the engine in 1, possibly 2 cylinders. Maybe a coil pack, maybe injector or spark plug. Second, my Speedometer doesn't work at all. Everything other than those two work aside from my air conditioner not being able to select where the air goes. Any ideas on any of these?
 


Is it throwing a CEL? Stupid question but did you replace the plugs and wires after the fire? Also, check the ground and the harness that connects to the ICM (the part UNDER the coil packs) for damage. Since I don't know the extent of the fire I would visually inspect ALL the harnesses around that area for damage.

As far as the HVAC not selecting where the air goes this may be a vac leak, would may also explain the miss now that I think of it. Check to be sure all of your vac. lines are good and none are cracked/missing/burnt.
 
The plugs and wires have been replaced. Now that I think of it there was a Vac line that I forgot to replace that ran along the left side of the engine. I went out today to check everything out. I have two dead cylinders. I have no power to two of the injectors and that is causing the miss. I know they aren't bad because I switched them with 2 known good ones and they didn't work so I took a test meter and found them dead. Could that be a ground issue or would that be in the ECM? The CEL is illuminated and I got the codes read at AutoZone. There were 4, but for some reason he only gave me 3. P0107- MAP Sensor. P0753- Shift Solenoid 3-4. And P0758- Shift Solenoid 2-3.
 
Could be a ground, but with everything being controlled by the ECM that may be the better place to start.

For the MAP sensor make sure its firmly seated in the housing and not cracked. This will cause a vac leak.

The shift solenoid issues may be a harness issue. Check the large harness that plugs into the trans and be sure it's tight. Also, since you have a 97 SE you still have the vac. controlled trans. IIRC. Check the vac. connections from the TB to the trans and make sure its good as well.
 
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