91 explorer hard to start and rough idle

[edcombs]

recently my 91 has started with a really rough idle. i mean it goes from around 600 rpm to 1100 or so. the thing is it doesnt do it all the time. it does most of the time but everyonce in a while it suns smooth as can be. it is also having a hard time starting up it has to turn over at least 6 times before it will fire. i have changed my plugs, wires, and fuel filter and have checked my tps and maf, and they are in good working condition? any one have any suggestions? Maybe pcv valve, fuel pressure regulator? fuel pump goin out?
thanks

 

[Roadrunner777]

Maybe clean the Idle Air Control... its on the intake manifold, driver side, longish cylinder thing. It controls the airflow at idle.

 

[mr cribb]

Before I would start tossing money at it.... I would check the fuel pressure at the regulator. That way you would know what the fuel pressure is.

Only thing I am leaning towards is maybe the coil pack.

Hope this gives you some areas to explore.

 

[Roadrunner777]

How is it, once it is driving down the road? I may not have been very clear in my first post, the IAC is just a simple air valve that can be removed with 2 bolts and cleaned with carb cleaner. Also, an interesting test is to tap this valve with the handle of a screwdriver when it is idling badly and see if it clears up. It looks like this:

 

[clownman2005]

ok mines kinda doing the same thing right now. friend at the auto parts stor was saying the same thing. he unplugged it and the whole thing changed couldnt tell if it was good or bad.
while idling sometimes it just misfires but almost like something plugs up a vacumme leak it raises the rpm and sounds fine. we found a crack in my intake tube, sealed that up, helped a bit for other stuff but it still goes thru the misfire and just throws gas away. i can smell it and it makes me sad
im gunna go buy a new iac and see whats up
but he also suggested fuel leak too. how do i test the fuel line pressure?

 

[TonkaRanger3.0]

clean your fuel system? check your fuel pressure and check for leaks in the lines

 

[clownman2005]

i heard those rubber hoses underneath will rot out and split?
i mean everytime i look into the fuel system it seems fine? then again the engines cold. possible that once its warmed up something will open up?
and i still dont know how to check the pressure

 

[TonkaRanger3.0]

is your engine 3.0 or 4.0?
theres a schrader valve on your fuel rail it looks like a valve stem locate it and get a fuel pressure tester it should be in the ball park of 60 to 90 psi

 

[TonkaRanger3.0]

the fuel rail is located on the intake manifold
:rangerred:

 

[mr cribb]

He has a 94 X so 4.0...

 

[MrShorty]

and i still dont know how to check the pressure

In the Under the Hood forum, there's a "fuel pressure test mini-diary" or something to that effect that describes how to test the fuel pressure on your engine.

 

[clownman2005]

i went to autozone and borrowed their tester and it wouldnt read anything. even when i started it there was nothing. i had like 3 codes pop up tho that i havent seen before
157, 332, and 528

 

[MrShorty]

BrooklynBay has a list of code definitions in the EEC-IV forum. CM 157 points to a (past) problem with the MAF circuit (is it possible this is something left over from testing the MAF?).

CM 332 points to a fault in the EGR system

CM 528 seems to indicate something wrong with the PNP (assuming auto tranny) or the clutch switch circuit (if manual transmission).

Since all of the codes seem to be CM codes, can I assume that it passed (111) the KOEO part of the test (the first set of codes output)? Have you tried the KOER test?

With multiple CM codes and nothing in KOEO or KOER, I'd probably start by clearing CM (see my notes on pulling EEC-IV codes thread), test drive, and see which codes come back to make sure you are chasing the most pertinent codes.