Switching on headlights causes rpms to drop dramatically.
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cheekychimp 
Director of Housing and Urban Development, and carbon/kevlar balls
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posted 01/02/12 10:54 PM   
Quoting stevep:
You make still have an ISC but it doesn't sound like it's working.
What the idle speed in the ECU set to? If it's not 950-1k then you have to have driven the ISC out of range (all the way closed) before the idle rises. The ISC won't do squat until the RPMs drop below the programmed idle.
Have you checked that the IPS is working? The ECU has to know that the throttle is closed before it will manage the idle.
I find missing throttle body ground straps on >50% of the car I see and on a DSM or GVR4 there used to ground the IPS so it can work.
Steve,
Thanks for taking the time to look at this, your input is very much appreciated but I get a bit confused by the different terminology that gets used. I'll try to go through this based upon my understanding of what you are asking.
As far as I know, the ECU has only been flashed for 560cc injectors and that wouldn't necessitate a higher idle so I am assuming it was set for stock but I don't know and I'm not sure how I can verify this without a chip reader.
The ISC could be an issue. No-one seems to know why but I purchased two brand new ISCs from the States and they would not work in my JDM throttle body. They were too short and would not close at all. I had a constant 1500 rpm idle. I went back to the JDM ISC and got idle back into the 700-1000 rpm range but it is a 2nd hand ISC and it may be worth investing in a new one. I can order one when I next go to the dealer. If the ISC isn't the problem it will be worth having a spare anyway.
What is the IPS Steve? Is that what I see some people refer to as the throttle closed switch? If so this could be an issue. I have an aftermarket S90 throttle body. The entire idle control assembly with the FIAV and ISC bolts on but I have a feeling that I no longer have a throttle closed switch. Will the ECU really not activate the TPS without this and is there anyway around this if not? If it is as simple as that, I guess I'm going to have to fabricate a bracket and switch assembly. Obviously without the throttle closed switch my throttle body itself is not grounded. If my ISC isn't being activated I doubt that will make any difference, but is the throttle closed switch the only item on the throttle body that requires a ground and could my solution be as simple as re-grounding the whole throttle body assembly?
It would help dramatically if you or anyone could explain any of the above. The car is so nice to drive at every other speed , I'd be willing to do whatever is required to sort out this issue.
Quoting fuel:
when you put the steering on full lock does the ECU attempt to bump up the idle speed or do revs drop also?
I haven't noticed any issues on full lock (I'll have to check), but I do have issues I noticed with the A/C turned on. That hadn't been an issue before because it was cold here so I had the A/C switched off. I'm thinking that my ISC isn't working as Steve suggested and that this throttle closed switch could be the culprit. I assumed my ISC was fine because despite blocking off my FIAV, I still got a higher idle when the engine was cold. Is that function of the ISC activated under a different circuit (coolant sensor)? If so it would make sense that my issue is simply that the ECU is not getting told that my throttle is closed and that it needs to activate the ISC.
But if that is the case wouldn't I stall every time ... or not necessarily?
EDIT: Confirmed! No throttle closed switch. Working on a fix for that!
Getting old sucks ... but it sure beats the alternative !!!
Edited by cheekychimp (01/02/12 11:45 PM)
Posts: 7333 | From: East Sussex, U.K. | Member Since: 04/19/04 | IP: (118.141.71.108) | 
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toybreaker
it's peace of mind at 100 mph plus
1990/2000
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posted 01/05/12 12:04 AM
Quoting grocery_getter:
So you physically do not have an idle switch? Easy. Use a 2G DSM tps instead of a 1G TPS. The 2G TPS is 4 wires instead of 3, the 4th wire is for idle switch. Done.
Think he runs the 90 style t-body, and the 2g tps won;t bolt to that. 
the bitterness of low quality remains long after the temporary joy of a low price has faded
Posts: 3541 | From: Never Summer Ranch, Colorado | Member Since: 04/30/06 | IP: (208.54.38.143) |
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stevep
Fixes ECUs
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posted 01/05/12 02:33 AM
Quoting cheekychimp:
As far as I know, the ECU has only been flashed for 560cc injectors and that wouldn't necessitate a higher idle so I am assuming it was set for stock but I don't know and I'm not sure how I can verify this without a chip reader.
Is the chip labeled in any way? Who made it, Jeff?
Quoting cheekychimp:
The ISC could be an issue. No-one seems to know why but I purchased two brand new ISCs from the States and they would not work in my JDM throttle body. They were too short and would not close at all. I had a constant 1500 rpm idle. I went back to the JDM ISC and got idle back into the 700-1000 rpm range but it is a 2nd hand ISC and it may be worth investing in a new one. I can order one when I next go to the dealer. If the ISC isn't the problem it will be worth having a spare anyway.
Can't help much here but if your comments in other threads on your harness having the pins incorrectly swapped and your comment about not having an IPS It's hard to conclude there really was a problem with the ISC. How are you attaching the new style ISC to the car harness? I got and continue to get the impression your car is early style so it would have the early ISC with a pigtail. I ask because I've seen people just follow wire colors making adapters and that's winds up connecting some of the coils reverse polarity so it steps in the wrong direction.
Quoting cheekychimp:
What is the IPS Steve? Is that what I see some people refer to as the throttle closed switch? If so this could be an issue. I have an aftermarket S90 throttle body. The entire idle control assembly with the FIAV and ISC bolts on but I have a feeling that I no longer have a throttle closed switch.
Noted below that your missing the Idle Position Switch = throttle closed switch.
Quoting cheekychimp:
Will the ECU really not activate the TPS without this and is there anyway around this if not? If it is as simple as that, I guess I'm going to have to fabricate a bracket and switch assembly. Obviously without the throttle closed switch my throttle body itself is not grounded. If my ISC isn't being activated I doubt that will make any difference, but is the throttle closed switch the only item on the throttle body that requires a ground and could my solution be as simple as re-grounding the whole throttle body assembly?
Correct, if the ECU doesn't see the signal get grounded by the IPS it doesn't know that the throttle is closed or that it should manage the idle. Yes, the IPS is the only thing on the intake manifold that uses the ground. As suggested below, if you can use a 2G TPS then use it and follow a modified 2G TPS adjustment procedure to get the switch to close when the throttle is closed and open when the throttle is opened slightly. Keep in mind this signal is one of the two that swaps around between 90 and 91. If you have a 90 stype ECU it should runs to pin 6 and if you have a 91+ style to pin 14.
Posts: 412 | From: St. Charles, IL USA | Member Since: 10/23/04 | IP: (24.13.253.79) |
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cheekychimp
Director of Housing and Urban Development, and carbon/kevlar balls
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posted 01/05/12 03:22 AM
Quoting stevep:
As suggested below, if you can use a 2G TPS then use it and follow a modified 2G TPS adjustment procedure to get the switch to close when the throttle is closed and open when the throttle is opened slightly. Keep in mind this signal is one of the two that swaps around between 90 and 91. If you have a 90 type ECU it should runs to pin 6 and if you have a 91+ style to pin 14.
Oh how could I be so stupid!
You have no idea how much I wish I had realized the significance of those two pins before now. The things you have said together with what Phil has told me in the JDM ECU thread are really starting to make a huge amount of sense now.
When I had idle issues initially and intended replacing the ISC I also thought with the car being a 1990, I would need pigtails to install a new one. I even had a member cut me a spare pigtail off a 1990 harness and send it to me. I was really surprised when we came to actually replace the ISC to find that the harness actually plugged straight into the ISC. Now it makes complete sense because Phil has been suggesting that only pre-facelift 88-89 JDM cars match the USDM 1990 DSM wiring whilst both my 1990 JDM cars are probably identical in configuration to the USDM 91 GVR4s.
Having been blindsided by the Fluidampr Pulley timing mark being off which I thought was the real reason my other car ran like crap, I think I have been creating my own problems with that car all along without realizing it because I swapped pins 6 and 14 when I clearly didn't need to.
Still good news if that is the issue. It should be an easy fix at the end of the day, I can run an EVO III/ 2G TPS in this car to fix the idle and I should be able to swap my wires back and hopefully get Link running in the other car now.
Getting old sucks ... but it sure beats the alternative !!!
Edited by cheekychimp (01/05/12 03:27 AM)
Posts: 7333 | From: East Sussex, U.K. | Member Since: 04/19/04 | IP: (116.48.253.81) |
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cheekychimp
Director of Housing and Urban Development, and carbon/kevlar balls
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posted 01/19/12 01:57 PM
Quoting fuel:
when you put the steering on full lock does the ECU attempt to bump up the idle speed or do revs drop also?
Mate, what were you thinking about here? I originally thought you were simply trying to establish if any extra draw on power made the rpms drop. Since I established rpms do drop on full lock however and since my problems occur mainly at low speed, I am now wondering if the power steering sensor is buggered as well. I don't think it's the only issue but it could be exacerbating things. I haven't located an EVO TPS to wire in yet, but as an experiment we unplugged the throttle closed switch on Ken's car and couldn't get his car to do what mine does, so whilst I don't discount what has been said, I also think there is a problem causing my idle to drop significantly so that it requires the ISC to intervene. It certainly seems that in general if things are set up well, the idle remains steady enough that the ISC just isn't needed.
Getting old sucks ... but it sure beats the alternative !!!
Posts: 7333 | From: East Sussex, U.K. | Member Since: 04/19/04 | IP: (118.141.65.201) |
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