So I have a 1997 Expedition with 5.4L Triton, that just recently began having a very weak idle, and it has stalled at stops. Runs strong otherwise, but just idles weak and sometimes stalls at stops.

So far I have cleaned the K&N, cleaned the Mass Air Flow, replaced the Idle Air Control valve and checked the hoses for holes or loose fittings. Still no real luck in solving the stall issue.

Any idea what else I can try? I am an extreme novice, by no means a mechanic but trying to learn and fight through this on my own rather than the dealer hitting me for hundreds.

Any advice, links, suggestions, etc is appreciated.

 

Have you checked for codes?

My 2000 is experiencing the same thing when warm. I had a P1121 TPS code so I replaced that with a MC one from Rock Auto. I also cleaned the MAF and IAC and it didn't help and I'm not getting any more codes. My next check will be the fuel pressure check and maybe a new fuel filter.

I suggest check for codes and check your fuel pressure.

 

Unfortunately I only have the basic OBD2 scanner and no CEL on or any stored codes.

 

When you replaced the IAC did you clean out the 2 air ports it covers?

 

Not really. I didn't have much of an angle on it and was unsure if I could spray it or anything so I essentially was just wiping it down and adding new IAC and new gasket only.

 

That's one thing I didn't do either, but I sprayed the IAC ports, butterfly, and intake from the intake side when the boot was removed. I was more worried about losing the straw when spraying.

Should I remove the IAC and spray it from the back?

 

The IAC works by regulating the airflow between the 2 ports. If either one is clogged and air doesn't flow, then the IAC has no way to regulate the flow and control the idle.

 

Thanks for the heads up. I did go back and clean the ports, but unfortunately no luck.

So far I have replaced Idle Air Control, replaced PCV and hose assembly, cleaned throttle body and mass air flow sensor, cleaned the K&N (did so and re-oiled prior to cleaning MAF) and looked for any bad hoses or clamps causing vacuum leaks but still haven't solved the issue.

It still will die after idling and seemingly is worse when the car is warm, and more prone the longer the car runs.

Any more ideas for a very novice guy on a budget trying to be a DIY Mechanic? I don't mind trying things bit by bit as its not my daily driver but I definitely can't afford to pay Ford to touch it!

Any more advice is welcomed and appreciated.

 

The only idea I have left without being there to dig into it is low fuel pressure at idle. Since you haven't mention any issue when driving I'm thinking the fuel pump is okay and the issue is more with the fuel pressure regulator. BTW, any idea how many miles since the fuel filter was changed?

 

Well today I decided to pull basically every portion of the air delivery system. Pulled each sensor, valve, hoses, air cleaner, intake, etc. Cleaned everything twice more, re-installed everything, and it SEEMS to have done the trick. I haven't taken it out for a true road test but had it idle in the garage for quite a while then around the block a few times with no stalls and no noticeable inconsistency in the idle. Will try to update after I get a chance to road test.