Z's r Best

My 86 IROC is stock.

I haven't driven it much the last couple of months or so due to all the snow/sand/chemicals on the roads (yes, even here in VA). All that mess and a cold morning issue.

Twice in the last couple of months I've gone out in the morning to start it up and drive to work (clear of road mess but well below freezing). It starts up fine but then begins to idle poorly and die. The check engine light comes on and on at first but then stays on even if the engine is sitting there idling. When it idles it won't take the pedal without stalling on me, even sitting there in park. I come home in the afternoon when the temps are in the mid to upper 40's and it fires up, no check engine light and no codes (except a 12) and runs just fine.

I think I've got some water in the gas tank or gas lines that is freezing up and restricting the flow of gas.

I could be wrong but since it isn't showing a code (I checked it yesterday morning when it wouldn't stay running and the check engine light was on while running and it still didn't show a code when I stuck the jumper on it and turned the key on - except that 12).

I did notice that the fan came on and ran when the jumper was in place and I don't remember it doing that before. Is my memory faulty or does the fan run with the "code reader" stuck into the ALDL terminal?

Think I'm going to get a couple bottle of that gas line water remover stuff and see if that helps it. Anyone have experience with that stuff working, or not working?

Thanks.

Viprklr

iTrader: (5)

yes to both

305sbc

iTrader: (3)

Hook up a laptop to datalog and see what's happening.
If you can find nothing wrong it may just be a loose ground or PROM pin connection. Is it a factory soldered-in PROM or has it been changed?

Z's r Best

Well, took it for a little trip yesterday, some stop and go and some interstate (about 25 miles) and it ran like a top.

Went outside a few minutes ago and it started up fine, suddenly the check engine light comes on and it dies. Sometimes it starts up, sometimes it doesn't. The check engine light will get bright, then dim, then bright again while its just sitting there with the key on (whether it is running or not).

I put the little code reader on it and can't even get a code 12 this morning. Nothing. The check engine light is one but no blinking, just steady (other than the bright, dim, bright thing).

I did notice that this morning the engine cooling fan is coming on when the key comes on even though the engine is about 45 F right now. The computer doesn't turn the fans on in an '86, right? Either the fan switch in the passenger side head or the pressure switch/sensor for the AC, right?

I've been driving that thing for years with no computer/electrical issues but now its bit me. I've heard a lot of folks complain that the TPI's were bad to have electrical issues but mine never has until now.

Oh well. Oh, no changes to anything. I've never even looked at the computer/chip.

305sbc

iTrader: (3)

It sounds to me like the ECM is losing connection to either power or ground.
Start looking for loose connections at your starter (check fusable links), around your battery, and behind the cylinder heads.
Make sure your ECM harness is engaged fully and not corroded.

Have you noticed any other electrical (headlights or interior light) dimming as well?

Z's r Best

Went back outside about 430 PM (warmest part of the day) to replace a couple of light bulbs (back up and front left park light). Put the key in and turned it to "on". The cooling fan came on and then shut off after 3 or 4 seconds. No way the fan should have come on when its only 55 F outside and the engine should have been about the same temp. Couldn't resist checking for codes again. Got a repeating code 12 only. Pulled the "code reader" out, hit the key and it lit right up. Idled fine, no check engine light.

I'll have to get the ohm meter out some morning when its cold. Whatever is going on seems to just be when its around freezing or lower. Once the engine is warmed up to 40/45 F it starts, idles and runs fine.

Thanks for the replies.

Z's r Best

I've got a couple of questions.

1. As far as I know the computer does not control the engine cooling fan, correct? It's either the temperature sensor/switch in the passenger side head or the pressure switch in the AC system if I remember correctly.

The reason I ask is the cooling fan is coming on when the key is turned on even though its only 40 F outside. The engine isn't hot but the fan runs with the key on.

2. Are the computers for an 88 Formula 305 TPI and an 86 IROC 305 TPI the same? Are the wires in the plugs/harnesses the same or do some of the wires in the plug have to be moved to a different place in the plug?

Asking this question because sometimes I can get a code 12 when I check the computer and sometimes the check engine light will not blink, just gets dim, then bright, then dim again.

I started to try to work on it today but those wind gust shut the door on me a couple of times and I thought it was going to rip the hood off so I figured I'd try it again tomorrow.

305sbc

iTrader: (3)

1. 86 Irocz TPI - The ECM does have control of cooling fan operation. It also has two other fan switches, but those aren't your problem. If you unhook power to your ECM, then turn your key forward again, you shouldn't see the fan come on.

2. Look on the outside of the ECM. They should both be 165 series computers, and interchangeable, though the CALPACKs would be different.

Your ECM is having issues. See my last post.

Z's r Best

Going out to look it over some more in a few minutes.

Everything else electrical seems okay. The only dimmin of lights are see is the check engine light which gets bright, then dim whenever I have the key on/engine off with the "code reader" plugged in. It either gives me a code 12 (everything okay) or the light gets bright/dim (but no pattern to that).

Not much wind now so I'm going to go check it out some more.

You know how this stuff goes. Yesterday I started it up, ran like a top, turned it around to put me and the engine in the sunlight and shut it off. Quit because of the high winds, started it up, ran great, turned it around and put it back in the carport and shut it off. For grins and chuckles I hit the key to start it up and it started the dying out crap again.

Thanks for the ideas/advice so far. Back in awhile.

86T/A_Ram_Air

it really sounds like you have an ECM issue...especially since somtimes you have a problem getting a code 12 which should always be present. i would check all the wireing for the ecm, if that checks out its most likely your ecm as before mentioned by 305sbc

TheNewStyle

I'm going to agree with most of the other guys, it sounds like ECU issues. At first I thought it was moisture in the lines but that can be solved with a couple of tanks of good gas and dry gas. You may look for cracked plug wires/harness wires or connectors. Because its sounding like you have minor issues with moisture that is developing overnight and evaporating during the day. Just my

supersquirrel

I have to agree with NewStyle it sounds like you have a moisture issue. Do you park your car outside or does it go into a garage?

Z's r Best

Well, my son pulled the computer out of the red IROC last week and put it in the black IROC. I've had it down the road and back twice (maybe 10 miles total) and its running like a top.

I'd forgotten how much FUN it is.

Oh, both are 86 IROCs with 305 TPIs, only difference is the rear end gearing and since '86's still had the mechanical speedometer I hope it won't be an issue (but then I'm not a computer expert so we'll just have to wait and see).