'89 Ranger 2.3L low idle

[bryanb]

making a new post, hopefully some fresh ideas show up.

Basically the problem is a low idle. Runs fine otherwise; starts fine, pulls good when under hard throttle. Engine wants to idle around 500 in Drive indicated on the factory tach, and feels very rough. Has never actually stalled though. When I say rough, its not erratic, its just chug-chug-chug-chug.... If I hold the gas pedal just a bit, in drive, at a stop, It'll idle smoothly at around 8-900.

I've replaced the IAC, TPS, MAP. Spark plugs look fine. The coil packs test ok. Cleaned the throttle body. Vacuum test comes up OK. Vacuum lines look good. I tried to set the base idle with the TPS unplugged, and last night i had it idling at 800-900 in Park. This morning it was idling at around 6-700 in park, and back to 500 in drive. Doesn't seem to matter where that idle set screw is set to, the computer wants to idle at 500.

Some suggestions I've had:
timing: The shop manual says that this is not adjustable, but there must be some base to set right? Else how do you know the timing belt hasn't jumped a cog?

ECTS: I changed out the one for the temp guage, but not the one for the computer, yet. Where is this one?

Air temp sensor. Where is this one? in the air cleaner box?

 

[chilsam]

Intake manifold

making a new post, hopefully some fresh ideas show up.

Basically the problem is a low idle. Runs fine otherwise; starts fine, pulls good when under hard throttle. Engine wants to idle around 500 in Drive indicated on the factory tach, and feels very rough. Has never actually stalled though. When I say rough, its not erratic, its just chug-chug-chug-chug.... If I hold the gas pedal just a bit, in drive, at a stop, It'll idle smoothly at around 8-900.

I've replaced the IAC, TPS, MAP. Spark plugs look fine. The coil packs test ok. Cleaned the throttle body. Vacuum test comes up OK. Vacuum lines look good. I tried to set the base idle with the TPS unplugged, and last night i had it idling at 800-900 in Park. This morning it was idling at around 6-700 in park, and back to 500 in drive. Doesn't seem to matter where that idle set screw is set to, the computer wants to idle at 500.

Some suggestions I've had:
timing: The shop manual says that this is not adjustable, but there must be some base to set right? Else how do you know the timing belt hasn't jumped a cog?

ECTS: I changed out the one for the temp guage, but not the one for the computer, yet. Where is this one?

Air temp sensor. Where is this one? in the air cleaner box?

It's in the intake manifold under the throttle body and upper intake.

 

[scotts90ranger]

have you adjusted the idle? With the IAC unplugged and the engine idling in park or neutral it should be around 500rpm, 8-900rpm with it connected. If it's too low, adjust the throttle stop screw in until it's where it's supposed to be. If that checks out, do a compression test... or there's possibly too much load on the engine from the tranny.

 

[scotts90ranger]

PS: If there aren't any codes for sensors (you have pulled the codes, right?), i wouldn't keep replacing them, unnecessary money spent...

also just saw you tried adjusting the idle, with what you have done I would check the timing belt (might as well replace it, it's not all that hard) and if that doesn't change anything I would do a compression test.

Also, the coolant temp sensor is located near the #2 injector on the top side

 

[bryanb]

Im expecting a new aircleaner box soon, from a fellow ranger station member. I'll be able to do more looking around then.

Yes, many times I've unplugged the TPS, and adjusted the idle. Every time it'll idle better, and then I plug in the TPS, and then it'll still idle better, and then the next morning, its back to the same crap. After the drive home from work last night, I have the idel screw a couple turns in, with everything connected, and running, and it went to idle at 1100 in park. This morning I didn't pay much attention, but seems to me in drive, it was at about 600, and smoother....

Haven't tried that with the IAC unplugged though. The Ford Shop manual doesnt mention setting the idle speed at all, nor timing, since its EFI, and DIS ignition. Is there a method of checking for base timing / checking for a slipped timing belt?

 

[scotts90ranger]

only way to check the timing belt is to take the front cover off and look at the marks

 

[bryanb]

PS: If there aren't any codes for sensors (you have pulled the codes, right?), i wouldn't keep replacing them, unnecessary money spent...

Code test passes! Only the 11 shows up. There was a 63 that showed up in the KOEO test, but I'll bet that was caused by my unplugging it the other day, with the engine running, and me messing with it.