Engine/Transmission (1998.5 - 2002) Bucking at full throttle

[JSchooley]

Need help.



Engine started bucking at full throttle. Feels like it is going back and forth from wot to limp at about 1 or 2 cycles per second.



I bypassed the boost elbow box from the MAP sensor and got the same results. Connectors look good.



Check engine light has not lit and truck runs fine otherwise. Fuel economy is same or better as indicated on the misinformation monitor.



Any ideas on what to check and how would be appreciated.



John

 

[PJStevenson]

Check your fuel filter.

 

[Hohn]

Look above^^. That's the first place to look.



Then, I'd check for codes. Flip the ignition off-on 3 times in a row, then watch the odometer window. If there's no codes, you'll just see "P done" after the "P ECM" or "P PCM" Otherwise, there will be codes in between.



there's always the remote possibility of a Crankshaft position sensor or a Cam position sensor, but those will usually throw codes and the symptoms are a little different.



Justin

 

[Piston Slapper]

She's running out of fuel. Probably the fuel filter as mentioned. It is a lack of fuel symptom anyway.

 

[JSchooley]

Thanks for all your inputs. I think I have located the problem in the blue box.



I thought the problem was there with the box off, however I am now unable to confirm that. Now it looks like it is there only with the box on.



No codes are set and the fuel pressure at the injection pump is solid. (I installed a guage on Thursday).