1G 1990 Eclipse Help identifying part

[Matthew Mills]

Hello,
I have been trying to fix my car. It runs poorly, way too rich. On Board Diagnostic says everything is okay. I noticed that when I have the key on and the engine off I hear a strange clicking noise from a part just below the throttle body. Here is a picture of the part, I am pointing at it with my screwdriver... i cannot figure out what it is from my manual, and my automotive friend is stumped too. Any ideas?

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Here is a zoomed out picture so you can see where it is.

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Oh, its a 1990 Eclipse GSX

 

[luv2rallye]

I'm not as familiar with the 1990 but it looks like the Idle Air Control Motor. Are there 6 wires on it (blue, red, yellow, white, red, black)? It's normal for them to click for a few seconds when key is first turned on.

 

[steve]

That is the Idle Speed Control motor on a 90. The clicking you hear is when the ECU homes the position at power up.

Very clean 90. The ISC and Throttle Position Sensor are unique to that year. Make sure that the ECU has or gets it's capacitors changed. Same for the TCU if it's an Auto.

 

[Matthew Mills]

The sound it was making was like a broken relay. it kept clicking very rapidly and randomly. I took out the throttle body to get at the second bolt, which was stripped and frozen, I had to drill out the bolt head.
The intake side was pretty clean on the throttle body but the back side and the ISC was caked in carbon. I was considering replacing the ISC but I am having a really hard time finding an exact match online. Most ISCs have the wiring harness attached to the unit, where this one has a cable that goes to the harness connector. The spacing is really tight, I don't think the STANDARD MOTOR PRODUCTS AC146 part will fit - https://www.rockauto.com/en/moreinfo.php?pk=445933&cc=1205525&jsn=344

I am going to try to clean the old part and test it. Also clean the throttle body to clear off the carbon.

So what is the issue with the capacitors in the ECU? Is it a known failure? My on board diagnostics doesn't show any errors.

 

[steve]

Yes, it a known issue. First electrolytic capacitors have a finite lifetime which has expired at this point. Second was a defect.

The seals around the leads fail and allow the electrolyte to leak out. It's corrosive and eats away at the copper and solder.
The 90 ECUs also like to catch on fire from the input power filter capacitor drying out and shorting.

The 1990 cars are unique in many ways, as you noticed the throttle Body and it's parts are one example but the ECU, Ignition and Gauge Cluster are another. Finding a replacement 1990 ECU is challenging and it has to be a 1990 model or you run into issue with the Ignition and Gauge Cluster. So you don't want yours burning up or rotting out. Replacing the 3 capacitors in it will avoid that problem if they haven't leaked yet or finding out they have and addressing it before the ECU acts up is cheaper than replacement.

There are three different types of ISC's, the 90, the 91+ and the late model black plastic version. The first two had a bad habit of the internal coils shorting and that would blow the drivers inside the ECU. I don't remember how common it was with the original 1990 version but the 91+ version was a common problem and swapping to the black plastic version seems to solve the problem.

Someone posted not too long ago that the modified a new ISC to fit a 90 TB. They aren't directly interchangable and require mechanical and electrical modifications.

 

[Dsm panda]

Thats me who did the 91 isc on a 90 and pull your ecu and check as steve said caps cause issues. My isc caused my ecu to fry the caps and isc driver. If you need any help let me know i can explain anything with the 91 isc you may need help with my cars running real nice after the guys at ecmtuning and a new isc.

 

[pauleyman]

Thats me who did the 91 isc on a 90 and pull your ecu and check as steve said caps cause issues. My isc caused my ecu to fry the caps and isc driver. If you need any help let me know i can explain anything with the 91 isc you may need help with my cars running real nice after the guys at ecmtuning and a new isc.

What about switching to a 91 up throttle body? Wouldn't that be easier?

I'm gonna jinx myself but in 26 years of ownership I've only ever had to replace one isc and it was on my original 90 when they were easily available way back when.

I know about the function but not about the swaps.

 

[AWD-Tony]

The intake side was pretty clean on the throttle body but the back side and the ISC was caked in carbon.

A leak from EGR might be causing the carbon build up. Use an impact screw driver or small vice grips when removing screws on the throttle body, and make sure it's the correct size. Those screws strip very easily.

http://www.ecmtuning.com/wiki/ecurepairhome

 

[Dsm panda]

If you do the tb you need a 91 fuel rail as well the 91 tb will hit on a 90 fr. and its easy to modify just had to oblong the holes so it fit then just exstend the harness and swap two wires. Imo if you just need the isc its cheaper and simpler. Not to mention you can now run the more reliable black isc.

 

[Matthew Mills]

Thanks for the advice! I cleaned the throttle body and the ISC. I tested the ohms and the coils are fine. I energized the coils and heard the click as expected but i didn't see any movement. Though if its a stepper motor it would need to be tested by the controller.

I took out the ECU and the caps looked clean, no leaks. I will still replace them. Just to confirm its the three caps circled in this picture. https://imgur.com/a/lRazB and not the ceramic cap slightly to the right of the other caps.

Looks like converting to a 91 throttle body is a good option. Has anyone tried a throttle body extension? An extra inch of clearance may be all thats needed.

I took off the EGR and its caked with carbon as well. Almost all of my vacuum lines are old and cracking. Any advice on where to get some hose for replacements?
Also the EGR has three vacuum lines and one electrical line, is that because the EGR is the valve and the solenoid together in one unit?

 

[motomattx]

No, its because you have a California emission model that has a thermocouple probe in the egr valve so that the ecu can monitor the flow of the egr valve. Your looking in the wrong places for an overly rich condition.

 

[AWD-Tony]

Thanks for the advice! I cleaned the throttle body and the ISC. I tested the ohms and the coils are fine. I energized the coils and heard the click as expected but i didn't see any movement. Though if its a stepper motor it would need to be tested by the controller.

I took out the ECU and the caps looked clean, no leaks. I will still replace them. Just to confirm its the three caps circled in this picture. https://imgur.com/a/lRazB and not the ceramic cap slightly to the right of the other caps.

Looks like converting to a 91 throttle body is a good option. Has anyone tried a throttle body extension? An extra inch of clearance may be all thats needed.

I took off the EGR and its caked with carbon as well. Almost all of my vacuum lines are old and cracking. Any advice on where to get some hose for replacements?
Also the EGR has three vacuum lines and one electrical line, is that because the EGR is the valve and the solenoid together in one unit?

Caps look fine and check the other side where they're soldered. Yes it's those 3. Also inspect those long black parts to the right. 1??? of those is your ISC driver. Did you replace the seals in the throttle body since you had it off?
Place your thumb lightly on the ISC and feel if it moves.
Bring the hoses to any auto parts store, they should have them.

 

[Dsm panda]

When my isc driver was out the isc just made a click insted of move inn and out like it should. I looked at it, it looked ok but the experts at ecmtuning tested it and found it to be bad. But my caps leaked as well.

 

[Matthew Mills]

OK. I took out the EGR, cleaned it, did a vacuum test and it holds a vacuum. Tested the flow with the vacuum off and on and its working properly.

I will definitely replace the gaskets on the throttle body, ISC, etc. and hoses.

The solder side of the ECU looks pristine, no weak solders, no shorts. So to confirm I need a 50v 22 micro farad cap, a 16v 100 micro farad cap, the big one I cannot figure out what the volts and farads are.
Here is a closeup https://imgur.com/a/3Wau8
Taking a look at this closeup it does appear that one of the smaller caps has leaked.

Pressing on the ISC with my thumb it wiggles barely 1/16". I will see if I can get it tested someplace. I went to my local race car place and they said they could order the original part for $540. I think I would rather get the plastic one and do some cutting and wiring before paying that much.

I am kinda stumped. I will put it back together if the ISC tests okay, but I don't think I found the issue. What else would causes too much fuel? I have checked the ECU, ISC, FPR, EGR, sparkplugs, etc. Could a vacuum leak somewhere cause this? *sigh*

 

[AWD-Tony]

Looks pretty bad. I'd send that in to ecmtuning and have them inspect it. I sent mine in thinking the caps were leaking but it ended up not needing repair. They're an honest company and service is top notch. Get the ecu back and recheck

 

[Dsm panda]

Yeah mine looked like that send it in youd be amazed how goofy a car can act when its brain isnt working correctly.

 

[AWD-Tony]

haha absolutely

 

[Matthew Mills]

Okay, Update Time.
I happen to be handy at electronics (I would not recommend doing it yourself unless you have worked on de-soldering, repairing electronic circuits. Electrical work only will not cut it.) so I took out the bad capacitors, cleaned up the electrolyte with flux and a heat gun, then some rubbing alcohol and a swab. Fortunately the other components did not get damaged so it was easy to clean. Took the old caps to my local Fry's and got replacements. Soldered the new ones in place and be sure to get the polarity correct. Also there are a few through-board solder points that you need to make sure still have connectivity near the capacitor holes. I put it back into the case and installed it.

Since I had the throttle body out checking the other things I cleaned them all up and got rid of as much carbon as possible. I kept the original Idle Air Control Motor since the coils tested fine. I didn't like the look of some of the vacuum lines so I replaced most of them, so of them are a pain to get to but it looks nice. I also had to change the coolant lines to the throttle body, not sure if that is just a California smog thing but they looked a little bloated in some places. I put the rest of the hoses in place and plugged the battery back it.

It started up after the fuel got into the lines and its running nice and smooth. I gave it a quick ride around the block and its running well at high and low speeds. Looks like the ECU was the culprit. I may have spent a lot of time taking things apart but I cleaned up a lot of the intake system, vacuum lines, spark plugs, etc. I think it will pay off in the long run.

Thanks for your help, i would not have considered the ECU without it! BRAVO!

 

[AWD-Tony]

Good job! Glad she's running good now

 

[Dsm panda]

Glad we could help!