89 sdv

I was on my way to pick up my check and I threw an ses light. I checked it when i stopped the car and got E26 and E62. Wwnt in to get my check, came out strarted the car and it just started revving like crazy so i shut it off right away. Tried to start it again and got the same thing. The battery was disconnected for about 20 minutes and I still had the same result. Called and figured out E26 was ISC related so I unbolted the ISC to get home just using the mechanical idle and that seemed to work ok for me.

Going to work and at work tonight I had trouble starting the car and kept enough pressure on the pedal to raise the idle so it would stay running and then I would let it go down to the mechanical idle which is 400-500rpm. During the time without the ISC connected the car was throwing E26 and the light would usually go off while slowing down or braking but back on again during acceleration which I assume would be normal with the ISC unbolted. I have done some reading here and came across the process for making the computer relearn the idle but is that my fix or is replacing the ISC going to be what I need to do? Would an ISC repair kit work instead of replacing the whole thing? Am I even looking at the right source with E62 showing up as well even though the E62 code doesn't show up with the ISC unbolted?

ISC Repair Kit Link - http://www.partsamerica.com/ProductDetail.aspx?mfrcode=NIE&mfrpartnumber=FE1405&parttype=487&ptset=A

:worship: I would reallyappreciate any help :worship: but until Saturday night I'll have someone else do my answering if anymore information is needed.

It MAY be your ISC, but it's possible that it's your TPS also. E26 sets if it detects the throttle switch closed (part of the ISC which happens when you let off the throttle), and the TPS is over 20 degrees. Basically the TPS is reporting how open the throttle is. If it's open more than 20 degrees, and that ISC switch is still closed, then one of them is malfunctioning. Either the ISC is bad (I never tried a rebuild kit, I'd just get a new one), or the TPS is...or the wiring to one of them is. Go into diagnostics, then press LO, then press HI. This should bring you to P.0.1, which is the throttle angle (calculated by the TPS). This should be steady, not jumping around, and it should increase as you press the pedal - direct relationship. If it doesn't, check the wiring to the TPS, or the TPS itself. If it behaves normally, replace the ISC.

E62 is the cruise vacuum solenoid. It means the solenoid is commanded off, but the feedback shows that it's on.

Tailfin has headed you in the right direction.

You need the FSM (Factory Service Manual) to properly calibrate (set) the TPS and ISC.

It is very likely that the TPS (throttle position sensor) has gone south, but on the other hand, the ISC stepper may be way off as well. The diagnostic procedure to set both at once is outlined in the FSM.

If both seem to test within tolerance and there is no binding of the throttle or cruise control cables, then I would start to suspect a vacuum leak.

On my 1991 Seville I had a crack on the vacuum port for the cruise control solenoid. Took me ages to find it, then put some super glue on the crack, let it sit over night. Worked fine after that.

Actually, I was just trying to get him to narrow it down first. If it is just the ISC, he won't need to calibrate the TPS.

The FSM procedure is not the easiest way to do that though, as I figured out when doing it to mine. That way tests the voltage and requires jumpering crap and I don't know where all that is lol... However, the diagnostic parameter - P.0.1, which I mentioned, tells the throttle angle. This value is calculated by the TPS, so you can use that and there's seldom a need to do all that electrical crap.

The simplest way is to retract the ISC by holding the throttle arm so it revs to 2000 or so...then push on the ISC plunger until it's all the way retracted...keep your finger or something between the throttle arm and the ISC plunger so it doesn't come back out, and unplug the ISC. This will lock it in the FULLY retracted position. If it isn't idling (warmed up) at 450 at that point, adjust the minimum air screw until it does. (the RPM can be viewed by pressing HI until you get to P.0.8)

With the ISC FULLY retracted (and only then), the TPS (P.0.1) should read 0, or as close as possible. If it is +/- 1 either way, it must be recalibrated. Unscrew the TPS torx screws and rotate it until it is. Then there is a learning procedure, which I always forget lol, by turning the key off twice while in diagnostics. That's all there is to the TPS.

Actually, I was just trying to get him to narrow it down first. If it is just the ISC, he won't need to calibrate the TPS.

The FSM procedure is not the easiest way to do that though, as I figured out when doing it to mine. That way tests the voltage and requires jumpering crap and I don't know where all that is lol... However, the diagnostic parameter - P.0.1, which I mentioned, tells the throttle angle. This value is calculated by the TPS, so you can use that and there's seldom a need to do all that electrical crap.

The simplest way is to retract the ISC by holding the throttle arm so it revs to 2000 or so...then push on the ISC plunger until it's all the way retracted...keep your finger or something between the throttle arm and the ISC plunger so it doesn't come back out, and unplug the ISC. This will lock it in the FULLY retracted position. If it isn't idling (warmed up) at 450 at that point, adjust the minimum air screw until it does. (the RPM can be viewed by pressing HI until you get to P.0.8)

With the ISC FULLY retracted (and only then), the TPS (P.0.1) should read 0, or as close as possible. If it is +/- 1 either way, it must be recalibrated. Unscrew the TPS torx screws and rotate it until it is. Then there is a learning procedure, which I always forget lol, by turning the key off twice while in diagnostics. That's all there is to the TPS.


The shortcut you suggest is okay if you know what the problem is.
I stand by the factory procedures.
The FSM procedure is VERY CLEARLY WRITTEN.
Once the ISC and TPS are properly calibrated, there is no guess work.

I don't recall a using jumper. I believe the jumper is part of the electrical test to ensure a good harness signal. But that is from memory and not the FSM procedure.

Actually, I was just trying to get him to narrow it down first. If it is just the ISC, he won't need to calibrate the TPS.

The FSM procedure is not the easiest way to do that though, as I figured out when doing it to mine. That way tests the voltage and requires jumpering crap and I don't know where all that is lol... However, the diagnostic parameter - P.0.1, which I mentioned, tells the throttle angle. This value is calculated by the TPS, so you can use that and there's seldom a need to do all that electrical crap.

The simplest way is to retract the ISC by holding the throttle arm so it revs to 2000 or so...then push on the ISC plunger until it's all the way retracted...keep your finger or something between the throttle arm and the ISC plunger so it doesn't come back out, and unplug the ISC. This will lock it in the FULLY retracted position. If it isn't idling (warmed up) at 450 at that point, adjust the minimum air screw until it does. (the RPM can be viewed by pressing HI until you get to P.0.8)

With the ISC FULLY retracted (and only then), the TPS (P.0.1) should read 0, or as close as possible. If it is +/- 1 either way, it must be recalibrated. Unscrew the TPS torx screws and rotate it until it is. Then there is a learning procedure, which I always forget lol, by turning the key off twice while in diagnostics. That's all there is to the TPS.

Would I need to have the ISC bolted back up during the retracting process?
I'm pretty worried about having the engine racing like that when I start it up.
I checked the P.0.1 in the ISC's disconnected state and it read -.6 so I assume i dont need to recalibrate.

Would I need to have the ISC bolted back up during the retracting process?
I'm pretty worried about having the engine racing like that when I start it up.
I checked the P.0.1 in the ISC's disconnected state and it read -.6 so I assume i dont need to recalibrate.
-0.6 is okay. Is not worth adjusment. How's your minimum air screw? Do you get 450-500 RPM (engine is hot) when throttle lever rests on it (ISC plunger retracted so that there is a 0.030" gap between th elatter and the throttle lever)?

Well I went ahead and hooked it up and was reading 3.7-4.1

Tried reading RPM in P.0.8 but it was just showing 25. Without the ISC in place I was getting consistant readings of .2 and -.2 for P.0.1. The minimum air screw would be the end of the plunger itself, right? Well that was out quite a ways as it has been since I got the car 2 years ago and turning it in slowed the idle some but then that snapped the plastic on the bottom of the plunger off. How far will this retract anyway? It acts like a clicking pen that wont seem to stay in.

Tried reading RPM in P.0.8 but it was just showing 25. Without the ISC in place I was getting consistant readings of .2 and -.2 for P.0.1. The minimum air screw would be the end of the plunger itself, right? Well that was out quite a ways as it has been since I got the car 2 years ago and turning it in slowed the idle some but then that snapped the plastic on the bottom of the plunger off. How far will this retract anyway? It acts like a clicking pen that wont seem to stay in.
NO! The minimum air screw is on the TB. It is a ctually the stopper for the throttle lever (and hence the TB plates) when the ISC plunger is retracted completely. Pay attention to posts. Make a search for "ISC" idle speed, throttle body, high idle etc. There is a lot of info on the subject.

Yeah, your TPS sounds fine then. With the ISC on and controlling the idle, 3.x or whatever is fine, because the throttle is open about that much because the ISC is holding it there for a proper idle speed...without it, or with it fully retracted, the RPM should be 450 (or 45 since P.0.8 is the speed/10). You say it said 25???...In that case, it sounds like you need to clean the throttle body, or something needs obvious adjustment... I don't even understand how the engine was running at 250....

P.0.8 is spark advance. P.1.2 is the rpm. Wasnt able to check the rpm. checked the fsm for that.

Is it? Sorry about that, I didn't realize they changed that in 1990...

My bad. It's actually P.1.1. for RPM and P.1.2 is MPH. That must have been changed in the TBI to MPFI change. Anyways, I picked up the $3 junkyard ISC motor and got the car running right again. I post back tonight if that has problems as well.

Also P.0.1 was reading between .5 and .9 so would it be a good idea to recalibrate the TPS because it doesnt sound to hard to do.

My bad. It's actually P.1.1. for RPM and P.1.2 is MPH. That must have been changed in the TBI to MPFI change. Anyways, I picked up the $3 junkyard ISC motor and got the car running right again. I post back tonight if that has problems as well.

Also P.0.1 was reading between .5 and .9 so would it be a good idea to recalibrate the TPS because it doesnt sound to hard to do.
My advice would be leaving TPS alone.