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high idle and reving
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pushkick
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PostPosted: Sat Nov 11, 2017 10:49 am    Post subject: high idle and reving Reply with quote

my 1990 vanagon 2.1 seems to have and new issue the idle seems to run a little high(1500) when it is cold and revs to about 2000-3000 rpm and then back to normal it keeps bouncing back and forth when it has been running for awhile.
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syncro2x
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PostPosted: Sat Nov 11, 2017 9:18 pm    Post subject: Re: high idle and reving Reply with quote

I had that problem on two different vans. Both time it was idle stabilizer control unit.
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pushkick
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PostPosted: Sun Nov 12, 2017 5:53 pm    Post subject: Re: high idle and reving Reply with quote

thanks for the input i was thinking it was throttle body switch that was out of adjustment but your comment seems more likely.
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syncro2x
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PostPosted: Sun Nov 12, 2017 7:51 pm    Post subject: Re: high idle and reving Reply with quote

I have had throttle body issues too. My idle just got high like 1500 or 1800 and didn't drop often, no surging up and down. Not an expert just personal experience. You might be able to find a used stabilizer control unit on here.
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syncro2x
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PostPosted: Sun Nov 12, 2017 7:57 pm    Post subject: Re: high idle and reving Reply with quote

See Van Cafe has rebuilt idle stabilized control units for 2.1 for $189. Surprised no one else has offered an opinion as screwy idles are a common vanagon problem.
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pushkick
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PostPosted: Thu Jan 11, 2018 4:48 pm    Post subject: Re: high idle and reving Reply with quote

i still have the problem and i got a new idle stabilizer controller. so now i was wondering if anyone has measured the input signals on the isc? or knows if there is a thread that has the signal levels.
here is what i measured running @ idle

wire
color_______ voltage _______ function

blk/y_______ 13.7 v ___________ power
Gy_________ 300mV _________ temp sensor
G __________ 6.6 v __________ distributor signal
WH/y ______ 57mV ___________ power steering sw
R/bl ________ 170mV _________ throttle position sw
R/blk _______ 1.5mV _________ ? bently says power
y _________ 2.29 v ___________ icv
wh ________.36v _____________icv

blk/y____ is not in bently , but definately power when ign on
Gy______ temp sensor signal seems correct
G ______ distributor signal seems correct freq is 300-350HZ
Wh/y____ power steering sw this seems correct while at idle
R/bl______ throttle position sw this seems wrong at idle
R/blk ____ bently say this is power seems wrong volts(may need to check)

any help is appreciated
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Last edited by pushkick on Mon Jan 22, 2018 3:40 pm; edited 1 time in total
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DigiMatrix
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PostPosted: Thu Jan 11, 2018 8:54 pm    Post subject: Re: high idle and reving Reply with quote

Do you have a copy of the PRO training manual? It has a whole section on checking the Idle Stabilization system (Page 30 - 33). Can be found here:
http://cabby-info.com/Files/DigifantProTrainingManual.pdf
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pushkick
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PostPosted: Mon Jan 22, 2018 3:30 pm    Post subject: Re: high idle and reving Reply with quote

DigiMatrix wrote:
Do you have a copy of the PRO training manual? It has a whole section on checking the Idle Stabilization system (Page 30 - 33). Can be found here:
http://cabby-info.com/Files/DigifantProTrainingManual.pdf


no i didnt have a copy thanks
i put a new idle stabilizer module in and the same problem still exist (high idle) checked for vacuum leaks and intake leaks and i could not find any.

this is the sequence of events when engine first heats up idle seems to be ok 900-1100 rpm. but after driving for awhile the idle goes up to 2000-2500 rpm. if i put in gear ( i have an automatic) the idle goes back to 900-1000rpm. any ideas on a trouble shooting solution?
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pushkick
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PostPosted: Wed Mar 07, 2018 8:19 pm    Post subject: Re: high idle and reving Reply with quote

using the digifant pro manual i checked the current going to isv and it is only 150 -210ma and fluctuating. the manual says it should be 450ma. following the trouble shooting in the manual the tps seems to be working correctly on idle but no high end continuity on tps. dont know what to do next
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pushkick
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PostPosted: Mon Mar 12, 2018 3:20 am    Post subject: Re: high idle and reving Reply with quote

what should the resistance reading for the idle stabilizer valve?
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pushkick
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PostPosted: Sun Mar 18, 2018 5:20 pm    Post subject: Re: high idle and reving Reply with quote

i got an answer from rmw and they tested a unit they had and it was 4.1 ohms.
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pushkick
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PostPosted: Sun Apr 01, 2018 5:43 pm    Post subject: Re: high idle and reving Reply with quote

i have replaced the hose from breather tower (crankcase ventilation) and the breather tower( hose was loose and worn and breather tower was clogged). but i still get high rpms when engine has run at 2000-3000 rpms for awhile (or 40 -60 mph). i checked isv , cleaned and tested with 12volts . it seems to snap open/close per tencent's post on operational testing of isv. engine seems to idle better and run more smoothly. but i still get issue with high idle and bouncing sometimes. i have replaced isc and cleaned/checked connectors and grounds and signals at isc. i am going to recheck signals at isc with: key off; key on; at idle; and 2000-3000 rpm. the current to isv was 150-210ma. but that was before i did all this work. i guess i will have to retest to see if it is now 450ma. if current is ok i am going to check the throttle body. engine idles fine when cold and starts ok. i havent found any leaks in air intake system . i may pull out my oscilloscope and look at signal to isv i assume it is a 12 volt squarewave from the distributor frequency signal (around 800-900 hz) that is on when in idle, ac on , power steering sw on, and on start up.
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blackglasspirate
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PostPosted: Mon Apr 02, 2018 8:29 am    Post subject: Re: high idle and reving Reply with quote

Last time I had something like this it was the ICU, but you said you've already swapped that. Have you done the wiring/electrical tests in the protraining manual? There's a table with quite a few of them that you can do from the ECU harness that will test the AFM, O2, TPS, etc.

Might be a good idea to get a baseline of those at least.

Also, have you tested the power steering switch? Maybe the wiring or switch itself is bad?
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pushkick
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PostPosted: Tue Apr 03, 2018 3:38 pm    Post subject: Re: high idle and reving Reply with quote

ok thanks everyone for the suggestions. i think i have fixed the issue with high idle and bouncing rpm's . it seems that the afm exit was bent a little and allowed unmeasured air into the rubber boot. i must have dropped or something never noticed that before. the hose from the crankcase tower was loose on both ends and was allowing air to get into the rubber boot at the afm to throttle body. i also disconnected the power steering switch and that seemed to eliminate the bouncing rpms. i used a vom and i was not seeing any fluctuation in input to isc module so i just eliminated it by disconnecting the switch and for now the bouncing has stopped and the idle is steady. again thanks for all the input.
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pushkick
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PostPosted: Thu Apr 05, 2018 6:15 pm    Post subject: Re: high idle and reving Reply with quote

this is really starting to suck!@#* it ran ok for a short trip after the items i mentioned above were corrected. then the next day it was back to high idle but no bouncing. i ordered a new a steering pump switch and disconnected the wires to the steering pump switch. idles fine and runs fine until run at 2500 to 3000 rpm for at least 10-15 mins.

i replaced throttle body gasket, temp sensor, and cleaned throttle body, disconnected a/c switch wire from isc. will see if this corrects issue. i also cleaned and lubed the isv. i noticed when i was cleaning throttle body there were small groves where the butterfly moves. this maybe the problem. i will have to see if the new temp sensor and throttle body gasket fix the problem. although i know when i disconnect the isv the engine works fine at idle and when at 2000-3000 rpm. so at this point it could be the temp sensor or the isv , isc(which i have replaced with a know good unit). the tps seems to work ok and every time. the tps cam seemed to look in good condition and works the micrswitch every time. i havent tried the cigar method as of this post but if the last things dont correct the issue i will probably test for leaks.
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i see said the blind man to his deaf dog
i am going to quit smoking and drinking and die a healthy man. gotta laugh
there is no deed to the planet earth
1990 vw automatic camper


Last edited by pushkick on Sun Apr 08, 2018 1:06 pm; edited 3 times in total
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Mark Lewalski
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PostPosted: Sun Apr 08, 2018 10:51 am    Post subject: Re: high idle and reving Reply with quote

Please keep us up to date on this problem.

I seem to have the same issues with mine and the next step I'm taking is looking for intake leaks... doing a Samba search for that now.

Thanks,
Mark
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pushkick
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PostPosted: Wed Apr 11, 2018 6:53 pm    Post subject: Re: high idle and reving Reply with quote

well after replacing the throttle body gasket, new temp sensor, cleaned isv and lubed, new isc, new throttle linkage spring (kick down spring ), new power steering sw (this seemed to stop the bouncing rpm's @ idle) and now i have disconnected the ps sw and the a/c clutch inputs to the isc. i am going to check isv for air flow when it is shut off because when i disconnect the isv the engine runs fine and dosent idle high. it takes a little longer crank on starter to get running when isv is disconnected and i have to push the gas pedal down but it seems to start ok. and run ok also i cleaned the throttle body and throttle butterfly it was gummed up and dirty but now it seems the engine idle adjust on throttle body is almost a 1/4 -1/2 turn from complete clockwise rotation. use to be 1/2- 3/4 turn from full cw rotation to get correct idle speed. i havent tried to pinch the isv hose to see how the engine runs with that or that hose off and put a piece tape on the end of hose. again this seems to only happen when the engine has been run at 2000-3000 rpms for at least 10-15 mins. then the idle goes up. if i let the engine idle for 30 mins after starting the it never goes above 1000 rpm.

this is the problem with closed loop systems that are a mixture of air and electrical and have no band limits/feedbacks on the input variables and output results/variables. basically an open loop system with no feedback.
very difficult to trouble shoot. every component has to be checked for correct operation and function in process and if it is an intermittent failure it can be almost impossible. at least with all software you can trap intermittent errors. enough for today tomorrow is another day and hopefully a resolution to this issue.
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Marshj
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PostPosted: Wed Apr 11, 2018 7:39 pm    Post subject: Re: high idle and reving Reply with quote

I also spent 8 hours plus chasing idle issues and got it resolved after many similar checks to you. My idle issue was on cold startup but similar symptoms. 1800 constant idle with IC Unit connected. I narrowed it down to IC Unit or an input that was off. With the Idle Control Unit unplugged it idled fine. This allowed me to determine one of the 14 ( I don’t have Bentley in front of me ) inputs was causing the error. I then traced those down and look for something that could give bad feedback. I tracked down a bad rpm input from the dash and simulantiousy soaked the ICU connecter ( the female receiver block ) in vinegar and washed with soap and water then blew it dry with compressed air. The goal here was to combat corrosion and I got clean looking copper from the female connectors. What do you know, the input issue was solved. Not sure if it was the behind the dash panel work ( just the top plastic housing and wiring related to ICU inputs ) or the cleaning of the connector block. But this solved the idle issue after days of frustration and slowing progress on other restoration projects.
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PostPosted: Wed Apr 11, 2018 8:00 pm    Post subject: Re: high idle and reving Reply with quote

Marshj wrote:
I also spent 8 hours plus chasing idle issues and got it resolved after many similar checks to you. My idle issue was on cold startup but similar symptoms. 1800 constant idle with IC Unit connected. I narrowed it down to IC Unit or an input that was off. With the Idle Control Unit unplugged it idled fine. This allowed me to determine one of the 14 ( I don’t have Bentley in front of me ) inputs was causing the error. I then traced those down and look for something that could give bad feedback. I tracked down a bad rpm input from the dash and simulantiousy soaked the ICU connecter ( the female receiver block ) in vinegar and washed with soap and water then blew it dry with compressed air. The goal here was to combat corrosion and I got clean looking copper from the female connectors. What do you know, the input issue was solved. Not sure if it was the behind the dash panel work ( just the top plastic housing and wiring related to ICU inputs ) or the cleaning of the connector block. But this solved the idle issue after days of frustration and slowing progress on other restoration projects.


i dont think the tach input from dash goes to the isc/icu i think the diz output goes to the isc/icu as a pulse width modulated (pwm) signal. i didnt mention that i cleaned the isc/icu connector to the isc/icu with electronic cleaner and checked the signals with a fluke.

i have looked at the isc/icu internally and it is just some opamps and some current drivers (transitors) with some logic gates that activate with the different devices (a/c, ps sw,tps,etc)

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pushkick
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PostPosted: Thu Apr 12, 2018 2:28 pm    Post subject: Re: high idle and reving Reply with quote

couldnt get xls file to display
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Last edited by pushkick on Thu Apr 12, 2018 3:45 pm; edited 1 time in total
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