Adventures with high idle.

Gairloch · 02-14-2006, 11:48 PM

I know there's a lot of people out there with idle issues similar to mine so I thought I'd document my process in troubleshooting my high idle here.

I finished swapping a '91 5sfe into my '91 NA about three weeks ago and the only issue I have left to nail down is a high idle.

The donor car was another '91 NA that is getting a v6 swap. The only real difference between the donor and my car is his has power steering and mine doesn't.

I used the intake manifold and throttle body off of my engine because my idle used to be a perfect 750 where his used to bounce a bit and it was a little cleaner. My idle is now ~2100 cold and ~1500 warm. When the engine is cold it will sometimes bounce a little but otherwise it's stable.

I've gone over the vacuum lines looking for cracked and misrouted lines but I haven't found any likely suspects. In the next couple of days I will be running the tests suggested in the BGB for testing and adjusting the TPS then if that doesn't do it I'm going to be pulling the throttle body to clean up the ISCV. Pictures of the process I take will follow.

PHOENIX · 02-15-2006, 04:02 AM

a few things to take a look at....

Properly blead coolant lines
intake manifold gasket (could be leaking air)

as far as the TPS, i would start the car, let it run till its warm (1500rpms) and then pull the harness out of the TPS and see if the car changes rpms (technically, the rpms should go up). if it doesnt, i would change that out with your spare from the other engine.

keep us updated! this sounds like it could be a great write-up

NDRCONSTRCTION · 02-15-2006, 07:38 AM

I've got the same problem with mine. It's a 92 turbo that has a jdm swap in it and it idles at about the same rpm.

Gairloch · 04-11-2006, 05:44 PM

This issue is such a hydra that putting together a write up for it is going ot be a challenge. I think what I'm goin gto end up doing is dumping all the steps I take here then trying to organize it after the fact. With that in mind ...

I've been struggling with an idle at ~1500 rpm since I swapped the 5sfe in it. I started going through the BGB trouble shooting steps last weekend and didn't really find anything until I got to checking out the AC system. (I'll note the specifc steps when I clean this all up, with pictures!) By closing down the idle screw in the AC VSV I was able to get the idle down to 1000.

I still don't think I've found the actual problem, I think I've found ways to compensate for a bigger issue. I've got the AC VSV and the idle speed control screw in the throttle body drilled all the way down. I've also got the butterfly opener set all the way to the minimum trying to make sure I've got as good a seal as possible. I'm wondering if "as good as possible" just isn't good enough and that is the source of my issues. I might have to get creative with some RTV or something to test it.

Is the throttle opener supposed to hold vacuum or is it supposed to be able to bleed out?

I don't know if it's related or not yet, but when I hit the button to turn on the AC compressor it doesn't seem to be coming on.

Gallagher005 · 04-12-2006, 02:14 PM

my idle for my 91 turbo is about 1,100 1,200 at cold start and i let the car idle for about 3-4 minutes before i drive and it drops to about 800-900 rpm.

Gairloch · 04-12-2006, 03:43 PM

^^ that's about what it should be. The warm idle range is 750-850 IIRC.

CTD20 · 04-17-2006, 12:32 AM

My 91 NA does something similar. After it sits for a few hours, you start it and the idle jumps up to ~2100rpm instantly, stays there a few seconds and falls to ~1500 rpm. All started after I cleaned the throttle body, unsure of the cause. I've checked the ISC motor and the TPS (both fine) and I don't wanna mess with the idle screw on the TB. I believe its a temp issue. The other day, it was 90 in Fontana and I went to start after it sat for 7 hours and the problem wasn't as bad. It didn't jump as high or stay very long.

I'm going to check the IAT and ECT sensors. I think the cold start injector might be firing a little too long when the thing is cold. I've heard bad ECT sensors can cause problems when the engine is dead cold and work fine the rest of the time. Depends on the thermistor setting (NTC/PTC). I'll keep you posted.

CyFi · 04-17-2006, 01:42 AM

ive got problems too, throttle plate is worn leaving a gap, and im pretty sure thats why its idleing at 1100 when warm. although when i press the ac button the idle doesnt change at all...

V6'er · 04-23-2006, 09:39 PM

Quote:

Originally Posted by CyFi

ive got problems too, throttle plate is worn leaving a gap, and im pretty sure thats why its idleing at 1100 when warm. although when i press the ac button the idle doesnt change at all...

Does your A/C work? If not, no idle change will happen.

Also, have you tried pinching that hose off with a pliers or vise grips? If the A/C Idle Up valve is leaking, that will make for a high idle.

CyFi · 04-26-2006, 04:37 AM

no my AC does not work, but which hose are you talking about i would like to try that.

V6'er · 04-26-2006, 07:29 PM

Well, no pics, but it mounts to the trunk firewall and has two hoses on it. One hose goes to the bottom of the ISC on the throttle body, the other goes to the intake.

02-14-2006, 11:48 PM	#1 (permalink)
Gairloch Dreaming of apexes Join Date: Aug 2005 Location: Minneapolis, MN Posts: 4,848 Thanks: 125 Thanked 258 Times in 228 Posts My Google Map iTrader Rating: (7/100% )	Adventures with high idle. I know there's a lot of people out there with idle issues similar to mine so I thought I'd document my process in troubleshooting my high idle here. I finished swapping a '91 5sfe into my '91 NA about three weeks ago and the only issue I have left to nail down is a high idle. The donor car was another '91 NA that is getting a v6 swap. The only real difference between the donor and my car is his has power steering and mine doesn't. I used the intake manifold and throttle body off of my engine because my idle used to be a perfect 750 where his used to bounce a bit and it was a little cleaner. My idle is now ~2100 cold and ~1500 warm. When the engine is cold it will sometimes bounce a little but otherwise it's stable. I've gone over the vacuum lines looking for cracked and misrouted lines but I haven't found any likely suspects. In the next couple of days I will be running the tests suggested in the BGB for testing and adjusting the TPS then if that doesn't do it I'm going to be pulling the throttle body to clean up the ISCV. Pictures of the process I take will follow.

02-15-2006, 04:02 AM	#2 (permalink)
PHOENIX Beams Owners Group Join Date: Mar 2005 Location: On Hiatus....... Posts: 7,914 Thanks: 84 Thanked 260 Times in 197 Posts Blog Entries: 1 My Google Map iTrader Rating: (46/100% )	a few things to take a look at.... Properly blead coolant lines intake manifold gasket (could be leaking air) as far as the TPS, i would start the car, let it run till its warm (1500rpms) and then pull the harness out of the TPS and see if the car changes rpms (technically, the rpms should go up). if it doesnt, i would change that out with your spare from the other engine. keep us updated! this sounds like it could be a great write-up __________________ - Dave Phoenix is finally back on the road with new suspension pieces, god she feels good!

04-11-2006, 05:44 PM	#4 (permalink)
Gairloch Dreaming of apexes Join Date: Aug 2005 Location: Minneapolis, MN Posts: 4,848 Thanks: 125 Thanked 258 Times in 228 Posts My Google Map iTrader Rating: (7/100% )	This issue is such a hydra that putting together a write up for it is going ot be a challenge. I think what I'm goin gto end up doing is dumping all the steps I take here then trying to organize it after the fact. With that in mind ... I've been struggling with an idle at ~1500 rpm since I swapped the 5sfe in it. I started going through the BGB trouble shooting steps last weekend and didn't really find anything until I got to checking out the AC system. (I'll note the specifc steps when I clean this all up, with pictures!) By closing down the idle screw in the AC VSV I was able to get the idle down to 1000. I still don't think I've found the actual problem, I think I've found ways to compensate for a bigger issue. I've got the AC VSV and the idle speed control screw in the throttle body drilled all the way down. I've also got the butterfly opener set all the way to the minimum trying to make sure I've got as good a seal as possible. I'm wondering if "as good as possible" just isn't good enough and that is the source of my issues. I might have to get creative with some RTV or something to test it. Is the throttle opener supposed to hold vacuum or is it supposed to be able to bleed out? I don't know if it's related or not yet, but when I hit the button to turn on the AC compressor it doesn't seem to be coming on. __________________ "Inside the car, the world beyond the driver's immediate horizon ceases to exist. Alone with the solitude of his desire, survival sense numbed by the speed, he's outrun the mediocrity of the outside world, slipped the shackles it tries to clamp on us all. He is running free, chased only by a fear of failure, for failure is to risk ejection into the real world." ~Mark Hughes

04-17-2006, 12:32 AM	#7 (permalink)
CTD20 Cornerworker Join Date: Mar 2006 Location: Simi Valley, CA Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Similar issue - 91 5s My 91 NA does something similar. After it sits for a few hours, you start it and the idle jumps up to ~2100rpm instantly, stays there a few seconds and falls to ~1500 rpm. All started after I cleaned the throttle body, unsure of the cause. I've checked the ISC motor and the TPS (both fine) and I don't wanna mess with the idle screw on the TB. I believe its a temp issue. The other day, it was 90 in Fontana and I went to start after it sat for 7 hours and the problem wasn't as bad. It didn't jump as high or stay very long. I'm going to check the IAT and ECT sensors. I think the cold start injector might be firing a little too long when the thing is cold. I've heard bad ECT sensors can cause problems when the engine is dead cold and work fine the rest of the time. Depends on the thermistor setting (NTC/PTC). I'll keep you posted.

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02-15-2006, 07:38 AM	#3 (permalink)
NDRCONSTRCTION No Skills Join Date: Nov 2005 Location: Asheville, NC Posts: 35 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	I've got the same problem with mine. It's a 92 turbo that has a jdm swap in it and it idles at about the same rpm.

04-12-2006, 02:14 PM	#5 (permalink)
Gallagher005 Watermelon Smasher Join Date: Mar 2006 Location: Arizona Posts: 573 Thanks: 10 Thanked 4 Times in 4 Posts My Google Map iTrader Rating: (1/100% )	my idle for my 91 turbo is about 1,100 1,200 at cold start and i let the car idle for about 3-4 minutes before i drive and it drops to about 800-900 rpm.

04-12-2006, 03:43 PM	#6 (permalink)
Gairloch Dreaming of apexes Join Date: Aug 2005 Location: Minneapolis, MN Posts: 4,848 Thanks: 125 Thanked 258 Times in 228 Posts My Google Map iTrader Rating: (7/100% )	^^ that's about what it should be. The warm idle range is 750-850 IIRC.

04-17-2006, 01:42 AM	#8 (permalink)
CyFi Shoulda put a ring on it Join Date: Oct 2005 Location: Phoenix Posts: 1,398 Thanks: 12 Thanked 38 Times in 35 Posts iTrader Rating: (11/100% )	ive got problems too, throttle plate is worn leaving a gap, and im pretty sure thats why its idleing at 1100 when warm. although when i press the ac button the idle doesnt change at all...

04-26-2006, 04:37 AM	#10 (permalink)
CyFi Shoulda put a ring on it Join Date: Oct 2005 Location: Phoenix Posts: 1,398 Thanks: 12 Thanked 38 Times in 35 Posts iTrader Rating: (11/100% )	no my AC does not work, but which hose are you talking about i would like to try that.

04-26-2006, 07:29 PM	#11 (permalink)
V6'er All Torque, All the Time Join Date: Apr 2005 Location: Charlotte, NC Posts: 872 Thanks: 0 Thanked 26 Times in 19 Posts iTrader Rating: (1/100% )	Well, no pics, but it mounts to the trunk firewall and has two hoses on it. One hose goes to the bottom of the ISC on the throttle body, the other goes to the intake.