Help for a friend. Missing 2.9L

[Jspafford]

A guy I work with has a 1988 Ranger with the 2.9L in it. He says when it is humid outside and he accelerates it hesitates and bucks. Sometimes it will clear up on it's own, sometimes it continues until he gets to his destination. He says it idles fine, it only runs rough when accelerating.

He says it has no CEL light.

 

[IMenriched]

A guy I work with has a 1988 Ranger with the 2.9L in it. He says when it is humid outside and he accelerates it hesitates and bucks. Sometimes it will clear up on it's own, sometimes it continues until he gets to his destination. He says it idles fine, it only runs rough when accelerating.

He says it has no CEL light.

Trust that you have suggested that tune up be done, or has been done resently. outside of that ....get the codes 1st.

could be many things...??? but hints of a vacuum leak.

 

[Jspafford]

He does a tuneup once a year. He says the problems been there for a couple years, but has gotten much worse this year.

He mentioned a long time ago he got a TSB for a MAP sensor but never had it replaced. Sounds like it might be at fault.

 

[Psychopete]

He mentioned a long time ago he got a TSB for a MAP sensor but never had it replaced. Sounds like it might be at fault.

Vacuum leak can cause MAP to think the engine is at WOT if it's not getting good vacuum at idle or cruise.

MAP is testable, but you'll need to know what the vacuum is to reference against the frequency that the MAP is outputting. FWIW, I think my MAP was still OEM (TFI module is very old as well).

Have you checked the FPR for leakage (or even better just a sanity fuel pressure test)?

His truck doesn't have a CEL, or does it not have a CEL present? +1 to pulling codes even so (KOER).

Pete