VG30DE hesitation

[kbflip02]

ok so ive posted in this in the J forum to no avail so i will try here...my car has a distinct miss @ 40mph and at 80mph if im under 3800rpms...if im over 3800rpms speed will continue to increase as if nothing happened...checked ecu...no codes...changed plugs, fuel filter, injectors, knock sensor, cleaned MAF and ran sea foam...am i forgetting something???

also cleaned IACV and EGR while replacing the knock sensor...its raelly beyond me....im not sure what else i can do....any info whatsoever would be GREATLY appreciated...thanks in advance

[GerryO]

Based on dirty MAF related problems on my '97 F-150, characterized by intermittent apparent slight "misses" at the shift points and pretty violent bucking at freeway speeds due to MAF affects on shifting, and my experience with correctly setting the TPS output voltage, when too low of a voltage will cause transmission hunting and higher rpms at crusing speeds, I'd focus on the MAF and TPS.

What are the rpm shift points and cruising rpms under fairly light pressure on the throttle, and what is the engine idle speed with the engine fully warmed up and the transmission in Drive at a complete stop, and is it stable?
Modified by GerryO at 12:20 PM 11/21/2008

[kbflip02]

Based on dirty MAF related problems on my '97 F-150, characterized intermittent apparent slight "misses" at the shift points and pretty violent bucking at freeway speeds due to MAF affects on shifting, and my experience with correctly setting the TPS output voltage, when too low of a voltage will cause transmission hunting and higher rpms at crusing speeds, I'd focus on the MAF and TPS.

What are the rpm shift points and cruising rpms under fairly light pressure on the throttle, and what is the engine idle speed with the engine fully warmed up and the transmission in Drive at a complete stop, and is it stable?

idla speed after fully warmed in park-800...rpms fully wamred while in drive 700rpms...it use to bounce between 700 and 900 but after i cleaned MAF its consistent....if you could show me where the TPS is and ill try that next....

[GerryO]

TPS is the black box in the photo and notice the length of copper wire inserted into the backside of the connector for the purpose of measuring/adjusting voltage with the engine running. Voltage between the TPS and ground should be between 0.040 and 0.045 VDC.

If you do make any TPS adjustments be sure to disconnect the TPS for a moment each time (with the engine idling and it should stumble), before reconnecting it to communicate the new closed throttle voltage to the ECM.

Are you sure it's an engine/firing miss? Coil pack? Ohm readings for each injector (about 11.5 ohms new)? RPM shift points? Engine misses are less noticeable at higher rpms.

[kbflip02]

TPS is the black box in the photo and notice the length of copper wire inserted into the backside of the connector for the purpose of measuring/adjusting voltage with the engine running. Voltage between the TPS and ground should be between 0.040 and 0.045 VDC.

If you do make any TPS adjustments be sure to disconnect the TPS for a moment each time (with the engine idling and it should stumble), before reconnecting it to communicate the new closed throttle voltage to the ECM.

Are you sure it's an engine/firing miss? Coil pack? Ohm readings for each injector (about 11.5 ohms new)? RPM shift points? Engine misses are less noticeable at higher rpms.

thanks Gerry ill check it out and let you know of my findings

[kbflip02]

how owuld one adjust the TPS?

[GerryO]

First step is reading its' output voltage with the engine fully warmed up and running at idle.

[ucox00]

May want to change coil packs. That sounds very familiar to my old problem.