Idle reves up to 2000 rpm

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Idle reves up to 2000 rpm

December 09, 2009, 12:13:48 PM

I have a idle issue, sometimes it starts climbing and gets to 2000 rpm or more and sometimes will not come back down till I shut the car off and re start, then back to 1000rpm, I have tried another IAC, and replaced the temp sending unit thinking it was sending the wrong temp to the ECM causing the problem, seems to be more stable now that the temp sending unit was changed but still revs up, TPS checks at about 0.92v and stays there when the engine is doing it's rev thing.
Removed the TB and intake and cleaned and looked over, it all looks good, cap, rotor, wires and plugs are in good condition and when the idle is steady it's good and steady and smooth, just every now and then will start climbing and sometimes comes down by it's self and other time does not seem to want to and sometimes I can rev it up over 3000 rpm and it will settle down, nothing constant to try to narrow this down, I would think a vaspoogee leak would be more constant, could it be a mis reading 02 sensor? can I remove and clean the 02 sensor?....or anyone have any ideas?

Idle reves up to 2000 rpm

Reply #1 – December 09, 2009, 01:54:27 PM

Maybe the TPS is bad.

Idle reves up to 2000 rpm

Reply #2 – December 09, 2009, 02:48:02 PM

Is it a 2.3 a 3.8 or the 5.0

Idle reves up to 2000 rpm

Reply #3 – December 09, 2009, 03:59:18 PM

Quote from: vinnietbird;301854

Maybe the TPS is bad.

Can the tps hold a correct currant and still be bad?

It's the 2.3 turbo...sorry for not putting that in the info.

Idle reves up to 2000 rpm

Reply #4 – December 09, 2009, 04:00:47 PM

Could the VAM be the problem and can you clean it like I do the MAF's on my other cars?

Idle reves up to 2000 rpm

Reply #5 – December 09, 2009, 04:44:53 PM

I had the exact same problem with my 87 turbo coupe. It had the 2.3lt motor, all stock. no modifications except a high flow aluminum radiator(if thats a mod, lol). I beat my head against the wall, i replaced the tps, the coolant sensor that connects in the heater hose right in front of the firewall(the car threw a code). Mine had 3 month old o2 sensors in it, so I don't think it was that. I originally thought it was only after boosting, but i proved that wrong after a while. I checked and cleaned everything that had a plug going to it that would carbon up and I could not find the problem. I took it to a shop and they couldn't find it. I posted it here as a problem. The link is http://foxtbirdcougarforums.com/showthread.php?t=20514&highlight=idle

I don't know if that will help.

Idle reves up to 2000 rpm

Reply #6 – December 10, 2009, 12:37:13 PM

Quote from: jpc647;301878

I had the exact same problem with my 87 turbo coupe. It had the 2.3lt motor, all stock. no modifications except a high flow aluminum radiator(if thats a mod, lol). I beat my head against the wall, i replaced the tps, the coolant sensor that connects in the heater hose right in front of the firewall(the car threw a code). Mine had 3 month old o2 sensors in it, so I don't think it was that. I originally thought it was only after boosting, but i proved that wrong after a while. I checked and cleaned everything that had a plug going to it that would carbon up and I could not find the problem. I took it to a shop and they couldn't find it. I posted it here as a problem. The link is http://foxtbirdcougarforums.com/showthread.php?t=20514&highlight=idle

I don't know if that will help.

So you never could find the problem?...What did you do? live with it or get rid of it?

Idle reves up to 2000 rpm

Reply #7 – December 10, 2009, 01:38:28 PM

I never found the problem. I chimed in because I figured if I told you everything I did, it might save you some aggrivation. I would have kept trying to find the problem, but the car sold. I told the guy I sold it to about it and he told me one of the guys at his shop would figure it out someday, he didn't seem to mind all that much. He was more concerned that the car didn't have any rust or repair work done to it.

Idle reves up to 2000 rpm

Reply #8 – December 10, 2009, 02:53:43 PM

I talked with a friend last night that had the intermittent high idle problem as well... While he wasn't totally specific(wasn't sure what the device's function was) apparently problem turned out to be a vac leak in the area of the over boost buzzer solenoid, possibly the controller it'self(back of passenger side strut tower)... Said he just plugged the line, no more problem...

Idle reves up to 2000 rpm

Reply #9 – December 11, 2009, 01:32:41 AM

start by pulling codes.

measure the tps properly as well.,,,below applies to a cfi engine but still applies to you either way.

tps test throttle position sensor
1 location-- vertical mounted on pass side of CFI with org/blk/grn wires.
Probe the green wire with positive lead of a meter and ground out
the black lead of your meter.

2 turn ign sw on ,, no start

3 the voltage reading on your meter should be around .5-.9 vdc.

4 operate the throttle linkage very very very slowly and note increase in voltage. Your increase should be smooth with no jumping and it should top out at around 4.6 vdc.

notes..
It is best to use an buttstuffog (needle type) meter when doing this step because it will detect flat or open spots on the variable resiseter (tps) better than the digital types.
you can bench test the tps buy hooking up to the green and black then black to org and measuring resistance and the two readings should match. The green wire is the center tap of the variable resistor. The resistance reading will be proportional to what you see in dc volts.

if you find your low end voltage is at or above one volt,, use a chainsaw file to file out the mounting holes so that you can mount and adjust the tps CCw to achieve the "less than a volt" goal.

when installing the tps,, lay it in place but slightly clockwise,, seat the tps then rotate it ccw to line up the mounting screws. There is a little pin up in the likage that will put your tps in a bind if you dont do this correctly. You cant just lay it on and bolt it down any old way.

Idle reves up to 2000 rpm

Reply #10 – December 11, 2009, 07:09:16 AM

Quote from: TurboCoupe50;301998

I talked with a friend last night that had the intermittent high idle problem as well... While he wasn't totally specific(wasn't sure what the device's function was) apparently problem turned out to be a vac leak in the area of the over boost buzzer solenoid, possibly the controller it'self(back of passenger side strut tower)... Said he just plugged the line, no more problem...

interesting.....

Idle reves up to 2000 rpm

Reply #11 – December 11, 2009, 08:25:14 AM

With care, thought, and patience you will find the problem. In my case it turned out to be a cracked EGR valve, but one that would intermittently hang just a hair open could also cause an intermittent high idle. What clued me in was that when I would pull the IAC connector, sometimes it would hardly idle at all. It was very rough and uneven, while other times it idled around 900 or so like it should.

Take your time and develop a plan of attack. Start with pulling codes and checking the usual suspects as others here have suggested. From there look for vacuum leaks or air leaks after the VAM. Don't forget about the PCV valve and hose which frequently have swollen through the years and need to be clamped in place to avoid an air leak.

Since it's intermittent, try to think if it's acts up when you change something. For example, does it only act up when you have the defroster on, thus indicating a leak in a vacuum actuator or a line going to one that moves the door for defrost.

Or maybe it only idles high after you have had your foot lightly on the gas pedal. Look for binding or worn linkage around the throttle body. Turbo Coupes have a fairly complex set of linkage here that was originally lubricated at the factory and can bind due to old hardened lubricant. Do not however simply lube this with old fashioned bearing grease! There is special lubricant designed for throttle linkage that doesn't get thick when cold that should be used.

The point is, really stop and think and you will be able to track your issue down.

Good luck! Keep your head on and you'll find it.

Shiny Side Up!
Bill

Idle reves up to 2000 rpm

Reply #12 – December 11, 2009, 04:21:47 PM

There are vacuum valves that are operated by solenoids. If the leak is down stream from the valve, you would only have a leak when the solenoid is energized.
If the car is 85 or older and you have ATC, there is a temperature activated vacuum valve on the heater hose that opens went the coolent is warm.