Hey guys--

So my 85 CDV is pretty much in top running condition, except for this lumpy idle that I can't sem to fix!:rant2: I've set the min air to be about 400-450 rpm (somewhere around there...idle is kinda lumpy down that low with no closed throttle connection), the TPS reads a perfect 0.50V at the min air setting, and I tried my best to "eyeball" the ISC gap at about 0.15"--didn't have a set of calipers or an accurate ruler, but for some reason, the ISC is hunting all over the place after about 4 seconds of idling nicely after startup in park, and hunts in drive. I'm also getting code E30 (ISC Circuit problem). Car starts nicely, but just won't idle properly.

Has anyone else had this problem? How sensitive are these engines to proper ISC gap? I installed a new ISC motor too. I really didn't turn the plunger in very far on the new ISC to obtain the proper gap--did this seem to be the case for anyone else?

Also, if someone could help me with the vacuum hose info I need that'd be great too! :)

The ISC circuit is built inside the ISC motor assembly. An improper gap will not set this code. The circuit can be checked.

There are four wiring ports that run into the ISC (a,b,c and d). With the D grounded and a 12v positive applied to the C fully retract the plunger of the ISC. Check the A and B with an ohm meter. Now do the oppisite with the C and D ports. This time fully extending the motor. Test the same with and ohm meter. If it does not test the circuit is at fault and the whole assembly should be replaced. A manual will be a better referance to what I am talking about.

Hi--

Thanks...however, as I said, I did replace the old ISC with a brand new one. I looked at the trouble code diagnosis diagram in the FSM, and in following it (my closed throttle switch is working properly) it appears that the code can be set if "after commanding the ISC motor to retract for 15 seconds, the actual RPM remained more than 150 and the throttle angle remained greater than 2.5 degrees " or if "after commanding the ISC motor to extend for 15 seconds, the actual RPM remained more than 150 below that specified and the throttle angle remanied less than 9 degrees." Causes are listed as: 1) misadjsted TPS, 2) misadjusted ISC motor, 3) defective ISC motor, 4) defective throttle switch (mine is OK), 4) defective throttle switch, 5) defect in wiring, 6) an ECM that is unable to process the signal.


I don't think my TPS is binding...it set just fine at 0.5V at min air and the voltage moved smoothly as I increased the throttle.

Any more ideas?

One thing I did notice in observing parameter P.0.1 when the ISC was moving is that the throttle angle never went over 4 degrees even as the motor was revving up considerably as the computer tried to test the maximum extension (I'm guessing it hit around 1400rpms or so). Does this seem right?

Something is off in the adjustment process. The minimum idle should be 525RPMs. I would retract the motor all the way following the manual. Start the car. It should be at 525RPMs. If it is not keep turning the ISC screw tell it is. The gap should be 0.06mm for those years (I believe). I would then do the maximum idle set. You should get a reading of 1.05-1.10v at the TPS with the ISC full extended. Loosen or tighten the screw either way to achieve this. A couple of times I have did this procedure the idle screw was touching the throttle lever during min set when I did the max I then had to back it down to achieve the voltage. Without any measuring devices to check the gap this is the only way to do it. Since you will have to have the key on to check this make sure that the key stays off for 15-20 seconds before trying to start it. It may rev really high the first start. Mine took two complete drive cycles to fully adjust itself properly. The max idle should be 1200RPMs when properly adjusted. If the car is at max idle at 1400RPMs that would be 200 greater then the 150RPMs alotted by the computer.

I read in your other post that you were having some vaccum diagram problems. I am not sure if this would have an effect but I doubt it. I am going to the junkyard tomorrow. There are two the same years as yours. I will take a picture and post them for you provided they are still there and visible.

Thank you so much! I really appreciate you taking the time to get some pictures of the vacuum hoses, as the diagram under the hood is really confusing when they're missing! I couldn't find any 85's in junkyards by me.

I'll first reset the min air a bit higher (it's around 400 rpms now), and then I'll go through and do as you suggested for the min/max extension voltages. Thanks!

One other question--

Do you mean the RPMs should be 525 at min air (i.e. with the ISC not touching the throttle plunger), or at idle with the ISC touching the throttle plunger?

Right now, my TPS voltage is set at 0.5V at min air and 400 rpms (with the ISC not touching the throttle). I simply removed the ISC motor to achieve the setting so the throttle plunger would rest on the throttle stop screw. Is this correct?

Regardless of whether it is touching or not it should idle at 525rpms. Then do the max idle. For some reason some of the ISC motors I have gotten are not seated completely or something when they are new.

I tried at the junkyard. I got a picture and then the batteries died on my camera. I came home to find a blurry, crappy picture. I will do something about it today (thursday).

24839

See what I mean.

I will try to take another picture. This time I will draw the break down too. If the picture remains crappy I will make it myself in the paint program on my computer. I actually have did this a couple times. I have quite a little collection on my computer of vaccum and belt stickers.

Thanks! If you can just take a picture of the hoses, that would be great!

Hi AllCads--

If there's any way that you could pull the ECM and BCM from that 85 car and send it to me, I'd be more than willing to send you a money order for your troubles. Mine are getting flaky (especially the BCM).

I can do that next week (wednesday or thursday off days). I got tided up today and could not get back to the junkyard today. The weekends I can not really do anything but work. I will talk to the guy next week. It should be semi cheap. Have to figure out shipping though.

There are actually two of them at the junkyard. One has high mileage (175K). The other one was rear ended and lower miles (105K). I will take it out of the wrecked one as I know why it is there.