Idle issue has me stumped

chadly

chadly

New member
I have been getting a high idle, around 2K in park, 1200 in drive. My first thought was a vac leak, went through everything but couldnt find any leaks.

On a hunch, I disconnected the battery for a few minutes and it ran fine for a couple days, then the high idle returned. I checked for codes but couldnt find any. Now whenever it starts doing this again I either reprogram the ecu with my X3, or disconnect the battery and it "fixes" it for a while.

I am thinking its a sensor, but which one? Any ideas or suggestions are greatly appreciated.
 
AnthraxBird

AnthraxBird

The Band, not the disease
IAC possibly, its easy to replace on Gen2's (about 2 minutes).
If its original, i would replace it.

Also, check your LT and ST fuel trim values.
 
chadly

chadly

New member
Never mind figured it out.

Since the fuel trim values are based off of (among other things) the O2 sensors, and a while back I had a code for a bad O2 (that eventually went away), Is it possible its the bad O2 causing this? Gonna change it out anyway, hopefully it fixes it.
 
chadly

chadly

New member
Honestly I dont remember. Something about Oxygen sensor ..... B2 lean. I should have wrote it down but I didnt. It will probably come back.
 
DLF

DLF

New member
chadly said:
Never mind figured it out.

Since the fuel trim values are based off of (among other things) the O2 sensors, and a while back I had a code for a bad O2 (that eventually went away), Is it possible its the bad O2 causing this? Gonna change it out anyway, hopefully it fixes it.
Click to expand...
Maybe ;)

It's also quite possible that the sensor is working correctly, and it's indicating another issue, such as a vacuum leak.
 
AnthraxBird

AnthraxBird

The Band, not the disease
It won't fix it. The sensor is doing its job, sensing there isn't enough fuel in the
mixture. It's either a vacuum leak, it could be a dirty injector etc. My best guess would be an intake manifold leak, or the imrc's. I say this because it's bank specific, if there are no other codes. I'd have to say drive it until it turns the CEL back on again, or check for old or pending codes :D
 
S

snub

New member
chadly said:
The IAC is about 4 years old. If I unplug it the engine dies so am I safe to assume it is working properly?
Click to expand...
I am no expert on this subject but I do know that when I unplugged the IAC valve on my '94, the idle returned to normal. The engine did not die. It just ran like crap until it warmed up. I would have to think the throttle blade is closing too far.

While I'm here I should mention this. I had my IAC valve replaced since the engine was idling way too high. Unfortunately, it was still idling high after the replacement. Not quite as high, tho. The mechanic told me to take it for a long drive to see if the computer would learn since the battery had been disconnected.

It idled down a bit, but not enough, so I took it back to him. He performed a procedure that he calls " Dead Braining" the computer. He removed both cables from the battery and held them together for 30 seconds. Apparently this drains the memory from the computer. He said the computer is capable of learning, but has problems 'unlearning'. He said he had to do this many times on Ford products when he replaced electronic components on the engine.

I drove the car a few miles, it now idles perfectly.
 
9

95blklsc

New member
It's strange, my 95 did what chadly was saying in the first post yesterday. It started and went to 2k and didn't come down. I checked for a vac leak, stuck throttle cable, MAF, etc. everything looked ok. It was at about 1200 rpm in gear. It finally calmed down by the time I got home and it has been fine since. No idea what it was but it left me a bit concerned.
 
chadly

chadly

New member
Haven't had time to mess with it, worked like 80+ hours this week. Hopefully will be able to find something out tomorrow. I did notice something I never noticed before, when the idle is acting all high, and I'm just cruising around at 25mph, the TC is locking up. I can tap the brake and it will unlock and RPM's raise. Not sure if that helps anyone.

Also, I keep getting a code saying the IMRC B1 is stuck open. Gonna run some seafoam through it and see if that helps. Can the open IMRC effect the idle?
 
DLF

DLF

New member
chadly said:
Haven't had time to mess with it, worked like 80+ hours this week. Hopefully will be able to find something out tomorrow. I did notice something I never noticed before, when the idle is acting all high, and I'm just cruising around at 25mph, the TC is locking up. I can tap the brake and it will unlock and RPM's raise. Not sure if that helps anyone.

Also, I keep getting a code saying the IMRC B1 is stuck open. Gonna run some seafoam through it and see if that helps. Can the open IMRC effect the idle?
Click to expand...
Maybe a bit rougher, but I have IMRC deletes and mine idles fine. :cool: It certainly wouldn't cause the idle speed to be higher.

Since you have multiple codes, O2's, IMRC's, etc., it sure sounds like you need to do some general maintenance.
 
chadly

chadly

New member
Thats what I figured (rough idle not higher).

Working 80 hour weeks for the last 9 months has left me little time for the car. Gonna take the time off tomorrow to work on it. I'll let yall know what I find out. Thanks for all the help.
 
AnthraxBird

AnthraxBird

The Band, not the disease
You can also reach behind the engine, by the firewall, and open and close the IMRC's by hand. See if its stuck :) Also, When O2 sensors go bad, 90% of the time it was a "O2 - Heater" code.
 
chadly

chadly

New member
UPDATE:

Tore into it today heres what I found out:
TPS = good
IAC = seems to be good
MAF = cleaned it really good, but it probably didnt need it anyway.

Still had same idle issue.

Looked for vacuum leaks again.... bingo.

On the upper manifold (98 Cobra), if your looking at it from the front, in the top right corner there is a bolt hole. At the bottom of that hole there is nothing for it to screw into. Evidently when I put it on I put a bolt in there and it ended up cracking the bottom of the manifold. I'll take some pics of it tomorrow or monday to explain it better. I'm thinking some JB weld will fix it up. Right now i got a big piece of duck tape covering it up and its idling fine.

Thanks for all the help.
 
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