I know there are lots of engine educated members here. My 92 Vette with only 57k started to run very rough and eventually would not start , no alarms came into the alarm console

I took it to the local Chevy dealer, who replaced the fuel pump and o2 sensors and claimed there were no alarms present when they were diagnotic testing for the problem, however with the new equipment they are getting a ECM [Prom alarm in constantly and the car still does not run. The dealer needs a new one.

The kicker apparently this part is not in stock anywhere in the country and he tells me GM just signed a deal with a supplier today and it will be at least a month before the part is available. ( The car stays parked at the dealer for the summer looks like)

Looking for some expert opinions. seems C4 Corvettes should have parts available everywhere, but apparently not the case, as I asked if they had tried after market suppliers like Eklers, which they said they had and no luck!

Any comments about this from engine experts? Or Chevy / GM personel?

A new GM ! Ok

Thanks

 

92 ECMs are hard to find. So the dealer isn't jerking you around about that.

The dealer is almost the last place I would take a C4 for service. Are there any Corvette specialty shops near you instead?

"would not start" is vague. Can you tell us if the starter turned the motor? any more details?

Why did the dealer replace the o2 sensors and the fuel pump? Was he guessing? did he really think that a failed o2 sensor (which is totally ignored durring starting) would keep it from starting?

 

Thanks for the answer, the car would only turn over but not start, it was sporatic tha last 200 miles (3 weekends i used it) I actually drove it to the dealer and for 3 days it would not repeat the problem , but it finally did for them
I too suspect they were changing parts to fix the problem, especially since no alarms came in previously, they changed the fuel pump and o2 sensors and now they have the. ecm prom problem , I did ask them how they determined the problem is that and their response is, it may be teh ecm, but they first need the prom replaced to determnine that.

Las Vegas, has lots of garages, but finding a good one is hard.

 

Rotation, compression, fuel, air, and spark. Those are the things needed to get your engine started and running. It would be nice to actually diagnose what is missing instead of shotgun replacing parts. If the starter turns it over we can check off rotation. I would dismiss compression out of hand since it was running ok recently.

Fuel. Ok they replaced the fuel pump. Was there any actual test to show there was no fuel pressure or an incorrect flow rate? Those are easy tests. I wouldn't pay for the FP unless they could show me they actually did the tests. The O2 sensor is just stupid though since it is imposible to test without a running engine and cannot keep one from starting. With fuel comes the need for it to be sprayed in batches (92 is batch mode) and that means we should have looked at the injectors for ohms and spray pattern. We should have been able to disconnect them one at a time if they ohmed out low to see if they were bringing down the bank. We should have been able to check to see if there was wet gas on a spark plug too. We should aslo be able to tell if the injectors are getting a pulse to fire.

Air. If there is nothing blocking up the intake (which I doubt since it ran ok recently) then air can flow ok enough to start it. It must be metered by the MAP (92 is speed density only), the throttle and the idle air controller. There are tests for each of these too.

Spark. Is anyplug getting spark? That is an easy test too. It is also easy to put #1 at TDC compression stroke and add a timing mark to the crank pulley and test the timing of the spark.

So the dealer says you need a new computer. Maybe you do. Can the dealer back that up with an explination of what is missing, rotation, compression, fuel, air, or spark and explain why he knows the comp is the fault?

 

Thanks for the information sir, I am going over tomorrow to discuss these things.

 

I have noticed in the past that several members have noted that the 92-93 ECM is a hard to come by part in the U.S. It is probably due to numbers of vehicles sold, but this ECM is very available up here in Canada. I needed one for my 92 last summer and received it by overnight shipping. I was going to buy two, to have one on hand, but the dude at the service counter told me that his supplier presently had eight in stock! I don't know about cross-border shipping and all that, but with the present value of your dollar to ours, it would probably be doable for you guys in the U.S. I believe I paid somewhere around $225.00 Canadian at the time.

 

Thanks Arbee, I am told I need the ECM "Prom" data bus to the ECM itself. wonder if there are any of those in Canada?

 

The 92 ECM is THE holy grail of parts for this year car. A rebuild is your best bet on a time resolvance.

 

WHY is that? I mean a Corvette is not a Vega or a Cavalier, who have been desposed of many years ago, there are many 92s still active.

2. I am told I need the PROM ( which is also none existent,) before they can test to see if the ECM is the problem.

The dealership believes a new Prom will do the trick. but am told one is not availble yet????? Does anybody know where a PROM for a 92 can be found?

I own 5 GM products including a 05 SSR which I also believe will be difficult in getting parts.

No wonder GM is going the way of Studebaker. **** Poor imho!

 

Huh? it doesn't make sense they would want to change the PROM without changing the ECU. PROM's don't usually die, they are just memory.

If you really need one I'm sure someone like PCMforLess could burn you a stock PROM without a problem.

I have a hypertech for a 6spd somewhere, PM me if you want to arrange a loan.

 

Doesn't the Hypertech piggyback to the stock PROM? He will still need a PROM, won't he?

 

Don't know, haven't taken it out of my spare ECU, just opened the bottom and I see the Hypertech chip. If it does piggyback then I have both for a 6 spd. I know the PROMs are different for an automatic.