first

Been fighting a strange idle issue on my 88 with the 5.8. Only when it's up to running temp while in gear it idles really rough when I stop at a light and sometimes dies if I don't tap the throttle in time. It will idle fine all day in park or nuetral. No one at my shop can figure it out. I've cleaned the IAC first then replaced it, TPS range is fine, MAP is fine, fuel filter is new, tune up, O2 voltage is switching, no codes, injector service, no vacuum leaks, fuel 32-35 psi @ idle, hell I even dragged out the Sun machine to check the KV's.

The thing that really grinds my gears is it doesn't do it all the time ecspeially when I pull it in the shop.

Any ideas?

Just call me Sean

iTrader: (1)

How about the upper intake gasket? There are problems with that sometimes. Bad throttle body maybe?

first

I've used up two cans of TB cleaner all over and no change. By any chance could the fuel tank selector cause an issue? I wish I could put a noid light on all the injectors.

aliens8mycow

Might check your battery leads - especially the grounds. Try replacing with 4 guage wire, including the one from the neg post to the front core support. It will also help to add one from the negative post to one of the throttle body bolts.

My truck was having similar issues, and this worked like a miracle.

first

Worth a shot. and I thought I've seen your truck before. I live in Liberty also.

aliens8mycow

Really?!?!? It's not blue/silver anymore - completely primered black in the past couple of months. ...started fixing some rust that develops under all of that trim, and ended up just going around the whole damned truck!

ymeski56

32-35 PSI's on the weak side.

first

well the idle has gotten a small amount better after further inspection of the fuel filter. The great ford tech that installed it for the previous owner crushed one side of it some how? I blew through it and sure as sh** it was fubar.

I don't think my fuel pressure is an issue. Runs an average of 33 psi @ idle when 30-45 psi is whats recommended. The high pressure pump has been change but I have had a bad pump right out of the box (Airtex)

Gonna rule out the cats here shortly with a set of shorties and true duals.

ymeski56

33 psi might fly at an idle. But not when RPM is increased on demand. Check at higher rpm. Also, what psi w/ vac hose on fuel pressure regulator disconnected?

first

Just looked up TSB's. Nice to be able to do that at home. Ford had a TSB in 1991 for a new idle air by pass kit for 85-91 ford vehicles. Anyone know about this?