'97 1Fz-FE naturally aspirated here,
Recently on a couple 2-hour trips pulling my camp trailer I noticed a lack of power uphill and over bridges. The first time it happened it threw a code for over fueling, did a little thinking and ended up reinstalling a cat that a previous owner deleted. The next trip it did it again, but it never threw a code, so I chalked it up to running 35s and factory gearing. Last weekend I did a 3-hour trip without the trailer, and it happened again, this time throwing P0171 (System too lean). I pulled over, cleared the code but within 10 minutes I noticed the code was already pending and I was severely lacking power. Got to my destination and cleared again planning to observe the return trip in a few days. Return trip was fine for the first two hours (same as before), then the same thing started happening in the third hour. It seems to get worse the longer I'm driving despite clearing codes along the way.
During the loss of power events it feels almost like I'm out of fuel. Any throttle position beyond barely open makes the engine surge like no fuel is being supplied. Deductive reasoning is telling me it's a lack of fuel and not a vacuum leak as it only happens after driving a long time. My first instinct is that fuel is getting hot enough that a weak fuel pump is struggling to keep up. My other thought (not knowing the system well) is that the FPR is weak and not holding back pressure high enough after fuel temps rise.
I haven't had a chance to put a gauge on to monitor pressure because I would likely have to intentionally have a several hour trip to replicate the conditions needed.
Any other thoughts on the subject would be helpful.
Recently on a couple 2-hour trips pulling my camp trailer I noticed a lack of power uphill and over bridges. The first time it happened it threw a code for over fueling, did a little thinking and ended up reinstalling a cat that a previous owner deleted. The next trip it did it again, but it never threw a code, so I chalked it up to running 35s and factory gearing. Last weekend I did a 3-hour trip without the trailer, and it happened again, this time throwing P0171 (System too lean). I pulled over, cleared the code but within 10 minutes I noticed the code was already pending and I was severely lacking power. Got to my destination and cleared again planning to observe the return trip in a few days. Return trip was fine for the first two hours (same as before), then the same thing started happening in the third hour. It seems to get worse the longer I'm driving despite clearing codes along the way.
During the loss of power events it feels almost like I'm out of fuel. Any throttle position beyond barely open makes the engine surge like no fuel is being supplied. Deductive reasoning is telling me it's a lack of fuel and not a vacuum leak as it only happens after driving a long time. My first instinct is that fuel is getting hot enough that a weak fuel pump is struggling to keep up. My other thought (not knowing the system well) is that the FPR is weak and not holding back pressure high enough after fuel temps rise.
I haven't had a chance to put a gauge on to monitor pressure because I would likely have to intentionally have a several hour trip to replicate the conditions needed.
Any other thoughts on the subject would be helpful.
