Hi all, first let me say I'm way over my head here. Last time I spun wrenches, other than oil changes and plugs, was in 1971, CJ5, so to be working on a 1992 C4 is way out there. Wife's car (baby) so I have to be very careful not to screw anything up.
About the car; bought new, dealer maintained, garage kept till 2002, covered outside since then. All stock, only mods except an analog phone in the center console. Automatic. Don't know the milage off hand, but it hasn't been driven or run much the last few years. Bevie is afraid it will leave her stranded. The engine was running rough in '07 and the dealership said she had sick gas syndrome. Ran the car off and on to burn off the gas, and filled up with new. Added stabilizer just in case.
OK, winter of '08 wasn't run much, and in the Spring we found evidence of a mouse nest in the center console. Ran OK that Summer, but Spring of '09 after a lube and oil change at Goodyear, first time it was ever not done at the dealer, the AC was blowing hot air on the way home. Back to Goodyear. Replaced a temperature sensor and sent her on her way. Next day AC blowing hot again. Sensor replaced at no charge.
Running rougher and hard to start.. Getting worse over time. Gas gauge stuck on full. Gas gauge fixed itself. No start, or hard start. Runs rough, searching for idle, trying not to stall.
This Spring dead battery. Replaced 750 ah Die Hard from Sears. Running, but barely. Now the dash is full of 8's and after a few seconds after key on, cycles garbage numbers and letters, stable for a second, all 8's, security light flashes three times and it does it again. Running or just key on.
More symptoms to follow. Any thoughts so far?

 

OK, back with more. I know this is long winded, but I'm trying to give as much info as I can.
First question you are going to ask is if I pulled codes. No, can't. Tried with handheld and by shorting A/B then A/G. A/B no response on area above console. A/G less mess on the dash, no 8's, but nothing readable. Handheld will not pull codes from a different '92 so try again with a different unit. Damaged ALDA? A/G short changed dash, but did not give codes.
Your second question will be if I have a FSM. No not yet, but I am planning to order one later this evening.
Other things I have noticed:
1. Little things, ***** at top of headlight motors spin when you hook up the battery. Normal?
2. ASR light lit sometimes.
3. Green light above AC off button flashing, sometimes.
4. Secondary cooling fan comes on, sometimes, sometimes just key on.
There is more, but I will stop here and pick up later with what was done last Saturday.

 

1. Yep, it spins when you hook the battery up.

You need the FSM, I'll bet grounds will be the first thing to check
Then chewed wires

 

You've got a car that is not only running mechanically rough, but digitally or electronically rough too! The car has sat for extended periods and Goodyear installed a sensor and then it seemed to go south and get worse.

Until you get an FSM, here's what I'd do. I'd check the harnesses leading into the ECM, look for corrosion and loose fittings. I'd check all the other harness connectors in the engine compartment, while I was at it, being careful not to damage the connector or the wiring. Then I'd be in the interior, especially the center console and looking under the dash and seeing if the mice built a nest up there too.

If you're getting crazy numbers on the dash, to me, that's an indication that the chips outputting the data to the display are either getting bad data, putting out a bad display or the voltages required for those chips to run is way off.

 

Thanks guys.
FSM now ordered. I agree that the first place to look is at the grounds. The problems have been getting worse over time, and to me that says corrosion somewhere. I have done a visual under the dash, but found nothing with the covers on. Checked all the fuses to see if they were good and right amps. All OK.
I've started checking grounds from a diagram I found on one of the forums, but main suspect is the CCU ground near the oil filter. Anyone confirm that location? Also anyone confirm CCU is behind radio?
Coolant temp sensor was changed by Goodyear. Any idea where that is.
More later on work done Saturday last. Brothers-in-law came by to help out little Sister. Wayne is a computer guy and Don a Toyota mechanic.
I handed tools and asked lots of stupid questions.
Got to get ready for work.

 

The coolant temp sensor goes on the lower right portion of the waterpump housing. You can see where it goes in the pic.

It sounds like the rodents have wrecked havoc with your car's electrical system. It's likely going to take an awful lot of time and patience to nurse your car back to health. As you've discovered, one of the worst things you can do to any car is leave it out in the elements (even with a car cover). Bad joo-joo, mang!



Definitely get a FSM. You can find some good deals on Ebay and you'll need the complete, two-volume set for your '92. I was able to buy both manuals in very gently used condition for under $50 (shipping included.)

 

OOH! pictures, great. Thanks!!! That helps a lot. Both FSM books on the way. I need them yesterday, so I paid a bit more than $50. Guess that is Bev's Anniversary present. Every wife should have one.

 

You're gonna' love those FSM's, then. They're chocked full of illustrations. Well worth their weight in gold. They'll pay for themselves in no time.

 

I've had my FSM set for a little over 3 years, just guessing they have saved me over $5k in labor. I think I took it to the mechanic once since I've owned the 92.

 

Thanks guys, that is encouraging about the FSMs.

More on what has been done and observations:
Prime suspects at this time;
Grounds
Short to ground draining battery (mouse)
CCU
ECM
VATS

Saturday before last I uncovered the car and tried to start, but battery was dead. Charged, and tried to start. Crank, but no start. Tried off and on during the day with growing frustration. No smell of gas that you would expect. Gave up and left it alone with full charge on battery. Finally got Bev to call her brother Don, the mechanic.

Last Saturday I uncovered the car, opened the hood and got everything ready before Don got there. Thought it wouldn't hurt to try to start it, but battery dead again. 5V in battery. Security light can't drain an almost new battery in a week. There has to be a drain on the battery; open relay or short to ground. Charging battery.

Don arrived a couple hours later and the battery was pretty good, enough to crank the engine, no start. Don suspected the ECM, so we started there, looking at each of the 4000 (OK, only looks like 4000) wires and checking the plugins. Nothing frayed or loose. Wayne, the computer savvy brother wanted a look inside. Disconnect battery, unbolt ECM, disconnect ECM. Opened her up, nothing visually wrong, no burnt smell. Removed and checked PROM visually. No corrosion all fine. Reassembled and reinstalled, hooked up battery, turned key on. Got hissing at the rail, and the secondary cooling fan came on. Both persisted for several minutes. Thumped on the ECM and both went off. Connector on ECM not snapped all the way in. Replugged.
Hummm, strange! Still cranks, won't start.

More later.

 

 

First, thanks to all who have read and especially to those who have responded.
Next, after reading about 60 hours of posts on this and other C4 forums in the last two weeks, I have learned a little. Mostly I have learned I was right thinking I was in over my head. This is like having a second job!
Update to The Usual Suspects VATS eliminated. Car starts. Coolant Temp. Sensor added. Goodyear actually changed it out twice right after the rough idle, popping exhaust started. 2008. That continued till this last bout started. Car is in "Limp Home Mode". (see further down)
Now back to the remainder of Saturday last.
Since we had been at at for 4 hours with not much headway we decided to break for lunch and regroup. Don's code reader was not working on the C4, but did work on his truck, No codes displayed by shorting ALDL, No FSM (ordered now). Lots of ideas, but mostly head scratching. Wayne was on his phone checking C4 forums and Googling like a mad man.
Don and I went back out and while he was checking voltages on the injectors and relays, I was doing key on/off at his direction. Tach goes to 1000.... Strange? Key off/on Tach at 700? humm... don't know. Any ideas?
Wayne comes out and says lets freeze the ECM. Why not? We had been throwing 15-20 amps at the battery for several hours and maybe there is enough bleed into the ECM to heat it up. Unhooked and unplugged and into the freezer for a half hour. Put ECM back in and hooked everything up. Key on, 888 on speedo, security light flash three times starts cycling garbage images same as before. But now there is a faint odor of gas in the engine compartment. Was none all day before this. Secondary cooling fan is off. Turned key, engine starts right up and idles fine. Either unplugging or freezing the ECM has reset it and allowed the car to start.
Car sits and idles real smooth no sputter or searching. Temp gauge is going up slowly, battery is charging, oil pressure and temp seem fine. Still idling temp going up normally.
Temp gets just beyond mid point, about where you expect the secondary fan to kick in, and the engine stops like you turned the key off. Now I know, cause it has happened before, that the engine will not restart till it cools down, about 15 minutes, and that is what happens.
Car is in "limp home mode" as I found out later after reading a post started by BIG K titled "Radiator fan on/Engine running rough" dated 12/13/2005. Answer and explanation by CFI-EFI. Very helpful information, thanks guys!
That ends Saturday's debacle.
Don came by Tuesday PM to take the ECM to a friends house. He has a 1992 C4 and said he was OK with Don plugging ours into his car to see how that went. More on that later. I started the engine while Don was here, and it ran fine up to mid point on the temp gauge. Then it shut off, as it did on Saturday last. No intervention by God.
I'm doing family stuff today and Don is working, but he is off tomorrow so we will get back to it with a different code reader. Codes would be a big help! FSMs on the way.
Not much we can do without codes. Need codes! Later.

 

Roger that. FSM's to the rescue! Keep us posted.

 

FSMs arrived last PM. Started looking over them at dinner, but quickly got a headache. Into book2 now since it is mostly electronics and I feel where the main problem(s) lie.

Re. the plug and play of my ECM in a different 1992 C4. Wednesday last
a. Started fine but idled at 1500 rpm thru full temperature range. No stall, sputter, or cutoff.
b. Analog oil & temp gauges OK, no data from digital display; temp or oil
c. Service ASR lit, same as on my car.
4. Secondary cooling fan on whole time.
f. Security light flash two times, random.

Don's scanner would not work on this car either with either ECM. Wrong software? Best guess.
Returned original ECM to friends car and all above disappeared.

What was the last year Corvette was produced without a computer?
May have to get me one of them!!

 

Returned original RCM to friends car and all above disappeared.What was the last year Corvette was produced without a computer?
May have to get me one of them!![/QUOTE]

1980 was the last year before the computer was put into the corvette.All 1981 GM cars to my knowledge had computers.Years ago I got a 1981 Chev. Malibu & removed the computer for some reason or another & the car still started & ran fine.Try that with a new car