Car won't idle after CEL and electrical burning smell

[jonnyp777]

My car has been running fine. Then this morning, after driving it for only a couple blocks from my house, the check engine light came on, and I smelt a kinda electrical burning smell coming from what i thought was the dash, and it may have been my eyes playing tricks on me, but it seemed like my interior got a little foggy. Then a few blocks later, i dropped below about 1000-750rpm, and my car died. So I started it back up again, drove, let off gas, and it died again. I parked it and took a quick glance under the hood (don't know what I expected to see), tried starting it again, and it won't hold an idle, and there is no CEL anymore. Seems to run fine when driving, just not when I let off. I was close to buying new plugs and wires for it because they have about a year and 8 to 9k miles on them, and i think they might have not been gapped right because my idle wasn't that great it seemed like. I have a stock 91 n/t with an injen intake and an ebay strut bar, and had all the belts replaced about 6 to 7k miles ago. I use 89 shell gas, which I've never had a problem with before. I tried looking around a little bit for answers, but am already late for work, so I'll have to look later, but I thought I'd just put my problem out there to get a headstart on some feedback. I'd really appreciate some help on this. Thank you.

PS: I'll be working all day today, so I won't be able to answer questions until tonight. Post what you can anyways with limited abbriviations because i'm not too familiar with a lot of them. And also, what type of spark plugs and wires would be best for a 91 stock n/t auto? with what gap? thanks.

 

[VETTE_50_TH]

If there is no CEL when you turn the key to on position, then you have a dead ecu. My car did that a while back, it would die, wait a little and the car would start, and die again later. If the smoke you saw could be the ecu burning up. Open up the right side of the console where the passengers feet would be to find the ecu. Open it up and smell it. If it smells like nasty fish , you have a dead ecu.

James

 

[jonnyp777]

Well then, I definately think I have a fried ECU. I will take it out this weekend to see for sure. I saw a thread in which case a ISC going out caused the ISC drivers to burn up. Could that have happened in my case? My idle was not that great, but that might have been to improper plug gaps. When I get a new ECU, should I unplug the ISC to see if the new ECU is fine, therefore concluding my problem?

 

[VETTE_50_TH]

I believe there is a way to find out if you ISC has gone bad, all it is, is a fuse. So if you can find the ampere or voltage rating for it, use a multimeter to check it. But, first find out if your CEL comes on. If it doesnt, no matter what you ecu is dead, or a fuse for the CEL is blown. But more than likely the ecu is fried. Hope that helps. Good luck finding an ecu.

James

 

[jonnyp777]

Well, I took out my ECU and it smells fried. Opened it up and found something burned up. I think it's a driver for the ISC because it looks like an ECU i saw in this thread. Here are a couple pictures of my ECU, but not as clear as the ones in that thread.

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Although, I tested the ISC, and all the coils or whatever read about 28 ohms. Isn't that what they are supposed to be at? But, it just seems like all the evidence points to that going out. Or is that not an ISC driver that's fried on my ECU? Just need to know so I can get it back on the road. And where's a good place to get an ECU? Thanks.

 

[VETTE_50_TH]

You coil should be much lower than 28 ohms. You isc looks good for the readings you got, but at this point, i would contact steve. Steve did my ecu, or i bought an ecu from him, he does great work. A lot of guys use him and not a single return i heard for dsmlink socketing. So he knows his stuff. Talk to him about whats happening and go from there.

James

 

[jonnyp777]

Can I have a full screen name for "Steve" please. Who am I supposed to know who that is? And just to keep this going for anyone else that can help, if it isn't the ISC, what the heck is going on? If it is, after I replace it, I saw in another thread that I have to "set the base idle speed if you put a new ISC in." So how do I do that? Is it in the manual, because I have that. And if you are going to help, try to be descriptive with no abbreviations, because I might get lost. And tell me what I need to do everything you describe. Thanks. I just really need to my car going again.

 

[VETTE_50_TH]

Alright, hopefully this will get you going. First, when you replace the ISC, which you dont need to do, reset the BISS back all the way down. That is located on the throttle body by the intake manifold. If you dont have one, MACH V sells them for 7 bucks. Anyway, reset that all the way down so when you ever had to replace the ISC, you know what that is. Basically, it controls the amount of incoming air when you are not on the throttle. Second off, you ecu is dead. You've pulled that out and looked at it. The "Steve" that i was referring to, his s/n is Steve. He is the dsm wiseman who does a lot of ecu fixes and socketing service for our cars. You can send away your ecu to him to take a look at it. Or see if he has one laying around. He is a very knowledgeable guy and nice to talk to. Here is a link to his business.

http://simon.chi.il.us/ECU/

Best thing to do, is to talk to him and see ehat he says. About you coil reading a high ohm, i would leave it alone for right now, and just replace the ecu first. And see how it runs, and go from there. Hope that helped.

James

 

[jonnyp777]

Thanks. So that's all i need to do to redo the idle speed? Just the BISS? I thought I saw somewhere about making sure the timing being 5 degress, putting the car in diagnostic mode, and grounding some stuff. What's that all about? Steve seemed to think that it wasn't the ISC's fault, but that a leaking capasitor caused the ISC driver to burn up. I don't know. Isn't my car probably due for a new ISC anyways? I heard should replace them every 75k miles. I just don't wanna take any chances of frying a new ECU right when I put it in, or somewhere soon down the road if the ISC is still good but decides to crap out. Uhhhhgggg. This sucks.

 

[steve]

Actually I gave you some possible reasons why you might measure all the windings good and still fry the driver.

Since I didn't measure the ISC myself I wouldn't say it wasn't at fault or not. They are the most likely cause but there are other ways and that's what we talked about. One of the ISC signals runs under C106 between the 12v and ground going to the capacitor. When the capacitor leaks there is a chance that the electrolyte will short the ISC signal to one or both. If it shorts to 12v that will blow the IC105 driver. Shorting to ground causes the ISC to malfunction but doesn't damage the ECU.

As you can see my user name is the simple yet confusing:

Steve

 

[jonnyp777]

Ah, thanks Steve. It's easier to understand written out. I get it now. Are there other tests for the ISC to make sure it's not going out though? I just don't want to have to go through this again in like 5-15k miles ya know? If I did end up getting a new one, I heard the new ones measure at like 40ohms, not 28, and that they are fine to use on regular ECUs. Is that true? Thanks. I'm gonna call around to some wrecking yards tomorrow to check for an ECU. Thanks again.

 

[luv2rallye]

My 99 Mitsu factory manual specs ISC coils at 28-33 ohms @ 68F.

 

[jonnyp777]

Here's the page where I read about the 40ohms thing. Read the paragraph right before the pictures. Is yours all black like that one?

 

[steve]

You coil should be much lower than 28 ohms.

You sure you didn't forget the n't on shouldn't?

My 99 Mitsu factory manual specs ISC coils at 28-33 ohms @ 68F.

That's what my manuals show for the original style ISCs.

If I did end up getting a new one, I heard the new ones measure at like 40ohms, not 28, and that they are fine to use on regular ECUs. Is that true?

That is my understanding from what the guys at DSMISC tell me.

 

[VETTE_50_TH]

My bad, haha. Gotta love those little things you miss, live turbo, vs. non turbo. Not that big of a difference at all. Glad you found "Steve".

James

 

[luv2rallye]

Ah ha! I fell for the n/t trap also. Thanks Steve.
My 99 Mitsu factory manual specs:
Turbo: ISC coils at 28-33 ohms @ 68F.
Non-turbo: ISC coils at 38-52 ohms @ 68F.

 

[steve]

No, it wasn't a N/T vs Turbo thing but a should vs shouldn't spelling thing that changed the meaning.

On a 1G the ISC is identical between the 2.0L non-turbo and 2.0L turbo car.
The 1.8L ISC is different, measuring 5 to 35 ohms @ 68F and has a different pinout.

 

[jonnyp777]

Well, I finally got an ecu. It should be coming in tomorrow or thursday. Can't wait to put it in and drive my car again. Still kinda debating on getting a new ISC or not. What was you guys do in my situation? I've heard of some other tests you can do to test the ISC. Could someone step by step help me with that if possible. If I don't get a new ISC, I'm going to be getting some new plugs and wires. What are some good brands for those with my set up (or lack of)? What is the proper gap? Thanks for all the help and help to come.

 

[steve]

The recommended spark plug is BPR6ES-11 for the 1.8L and 2.0L NT engine with a gap of 0.039 to 0.043 in. They should be torqued to about 15-18 ft lbs.

Remember that all the original capacitors used for C106 and C108 will leak so if the replacement hasn't had then replaced do so right away. I would leave the ISC unplugged until you know for sure it wasn't the cause.

Steve

 

[jonnyp777]

I bought it at Kragen. I'm sure it's a remanufactured one, so should it have newer capasitors on in? It does come with a one year warrenty though. So I just need the basic NGK plugs. Are the BPR6EIX-11 plugs like for turbos or something, or could I use them on mine? Or would I not gain much? I'm just tired of having bad city mpg. And I'll probably get some NGK wires too. What do you think? Thanks.

 

[steve]

Are the BPR6EIX-11 plugs like for turbos or something, or could I use them on mine?

Those are the more expensive NGK Iridium IX plugs.
You might gain some MPG but their big advantage is not having to change the plugs for 30 to 60k.

 

[jonnyp777]

Hmm, I might go with those then. How do you re-gap them? From what I've heard I don't think it's that hard, but I've also heard about different ways of doing it. They come .044, so I'd still want them between .039 and .043 right? And, what will happen if I leave the ISC unplugged? CEL? Bad idle all the time or just on cold start up? And, since the ISC is shorted out, will it show a CEL code if I do connect it without starting the car? Or, if it is bad, will it cause any current to flow to it, therefor not being able to have to much current to fry the ECU again? Sorry for all the questions, I just want to run as best as I can. Thanks.

 

[jonnyp777]

Well, I got the new (re-manufactured) ECU in, the new ISC in, did the above BISS thing, and wouldn't you know it, my car is running again. Wooo freakin' hooo! 320 bucks poorer, but oh well. And I also found out my intake was sitting on my a/c line and had been wearing it down. Good thing I found that (although in the only place I could think to put it now, it kinda hits the hood I think so I'll have to put some foam there or something). I also took the intake silencer out while I had the intake out to let the INJEN pur a little nicer. Thanks for all the help. Guess I won't be needing a Honda right now, but I still might put my car up for trades on craigslist to see what I can get for it because I really miss driving a 5 speed. Later homies.