Get Bent
TYF Newbie
- Joined
- Feb 8, 2017
- Posts
- 17
- Reaction score
- 0
I have a 99 Tahoe with random misfires on 2 and 3 that I have been trying to diagnose for months. I have replaced the cap, rotor, wires and plugs with ACDelco parts. I swapped out the coil and ignition control module with a spare I had and still have the misfires.
I put a PCM from Black Bear Performance in it and when I was taking it a mechanic to get the crank relearn done to get rid of the P1336 code, that is when the jerking on acceleration started. I had changed the crank sensor about 6-8 months earlier and this behavior was similar to what I was experiencing then, so I changed it out before having the crank relearn done. Unfortunately, this didn't solve anything.
I thought the new PCM was causing this, so I swapped it back to the original, but again nothing changed.
I unplugged the MAF sensor and nothing changed. I took it to a mechanic and he diagnosed it as being the distributor. So I replaced it with an ACDelco unit ,but it didn't solve anything.
I also checked fuel pressure:
KOEO: 54psi
Idle: 49-50psi
Operating range: 48-58psi (driving home)
Bleed down results:
56psi-0min
51psi-18min
38psi-36min
34psi-45min
33psi-49min
31psi-54min
30psi-58min
I used an endoscope to see if the injector nozzles on 2 and 3 were leaking. The image was a little grainy, but I didn't see anything. I am leaning toward the spider, because I don't know what else it could be. It seems to me that if it was the fuel pump, my problems would be more evenly distributed over all cylinders than just 2 and 3.
Well I replaced the spider with an ACDelco 217-3029. Fuel trims got way better so initially I thought it was finally fixed. NOPE! Believe it or not, now the misfiring cylinders are 1 and 2. I am beginning to think that my problem is a bad ground.
I put a PCM from Black Bear Performance in it and when I was taking it a mechanic to get the crank relearn done to get rid of the P1336 code, that is when the jerking on acceleration started. I had changed the crank sensor about 6-8 months earlier and this behavior was similar to what I was experiencing then, so I changed it out before having the crank relearn done. Unfortunately, this didn't solve anything.
I thought the new PCM was causing this, so I swapped it back to the original, but again nothing changed.
I unplugged the MAF sensor and nothing changed. I took it to a mechanic and he diagnosed it as being the distributor. So I replaced it with an ACDelco unit ,but it didn't solve anything.
I also checked fuel pressure:
KOEO: 54psi
Idle: 49-50psi
Operating range: 48-58psi (driving home)
Bleed down results:
56psi-0min
51psi-18min
38psi-36min
34psi-45min
33psi-49min
31psi-54min
30psi-58min
I used an endoscope to see if the injector nozzles on 2 and 3 were leaking. The image was a little grainy, but I didn't see anything. I am leaning toward the spider, because I don't know what else it could be. It seems to me that if it was the fuel pump, my problems would be more evenly distributed over all cylinders than just 2 and 3.
Well I replaced the spider with an ACDelco 217-3029. Fuel trims got way better so initially I thought it was finally fixed. NOPE! Believe it or not, now the misfiring cylinders are 1 and 2. I am beginning to think that my problem is a bad ground.