Our 2001 F150 is giving me fits! It does this weird little surge, burping and farting away...but only in ambient heat. The engine never gets hot, it never over heats. What have we done? A full tuneup with new plugs and boots, oil change, new air filter, gas filter. It did it again...took it back in and had the fuel pressure checked, fuel injectors are fine...it can't be the fuel pump, it runs great unless it is hot weather. It has twice blown the P0171 system lean bank 1 code and has gone away after the tuneup and again after the new o2 sensor. It runs great, except in hot weather, starts surging and losing power...so frustrating! Anybody have any ideas? I love this truck but at great cost

 

why can't it be the fuel pump?

 

It only happens in hot weather...the fuel pump is electronic...it would be funky all the time. Our mechanic checked it out...he is also running out of options.

 

all right then

 

Why do you think it might be the fuel pump??? Inquiring minds, you know

 

intermittent fuel pump operation is pretty common.
i'd check the fuel pressure when it's having the problem.

 

Vacuum leak was what it was on my 5.4.
Pete

 

Thanks...leaning towards vacuum leak. Already check fuel pressure

 

Use a Scanner to look at the signal from the IAT during the time it acts up.
You may find the signal at or near an out of limits reading.
It affects fuel and timing and of course varies with airflow temperature changes into the intake, from the outside.
Good luck.

 

How bad is it surging? What engine is it? My 1998 F250 LD Lariat w/5.4L Triton used to surge at idle a few hundred RPMs and it ended up being a leak in the intake manifold gasket. Replaced gasket, no more surging!