1997 Engine / Transmission Problems

[rcman989]

It was cold in Northern Minnesota this winter (-30F) and it was doing it then as well, so ambient air temperature doesn't seem to cause it. Thanks for the suggestion though. Still thinking it is fuel pressure related but just don't understand why one day it bogs when at speed, but the next day it will be fine even when the truck is warmed up at normal operating temperature.

 

[SAATR]

It was cold in Northern Minnesota this winter (-30F) and it was doing it then as well, so ambient air temperature doesn't seem to cause it. Thanks for the suggestion though. Still thinking it is fuel pressure related but just don't understand why one day it bogs when at speed, but the next day it will be fine even when the truck is warmed up at normal operating temperature.

Pumps can have intermittent issues. That's why checking the fuel pressure while you're driving and the issue is occurring is important for a proper diagnosis.

 

[df2x4]

You mentioned that the truck threw the P1621 before and after the tune. When you got it tuned, did you re-program your factory PCM or did you swap it with a different one and do the crank re-learn? Just curious because everything I'm seeing on google related to that code points to either PCM memory corruption or low battery voltage, with a couple exceptions involving people using aftermarket programmers like Bully Dogs. I'd check your electrical system out but personally I'm leaning towards some type of PCM damage if you haven't tested it with a different one.

 

[rcman989]

Just to clarify the P1621 code only showed after the tune was done. The hesitation/ bogging problem happened before and after the tune. It had the check engine light flashing yesterday and I finally was able to check it and it was fuel system too rich, and cylinder 7 misfire. So a fuel pump does not seem to be the problem since it was too rich. I was thinking it could possibly be an upstream O2 sensor causing the Air/Fuel ratio to be out of whack? Causing too much fuel and it bogging since the fuel won't combust.

 

[rcman989]

For anyone else who may have this problem in the future, problem fixed, O2 sensor replaced on driver side and runs great.

 

[Big D]

weird...

glad you got it fixed.

 

[rcman989]

I take my previous statement back. It did it again today, but definitely not as bad. It is still running rich, but seems to only be on the odd side of the engine, or at least cylinder 7 seems to always be the one misfiring.

It is a brand new O2 sensor and still reads high voltage on Bank 1 Sensor 1 P0135. What will cause this?