Hi people, I'm new to here.
I have a problem with my truck, a '90 s-15 with 4.3 TBI/700r4. When I would drive it the CEL would come on flashing and the motor would not run as good, less power, high idle, bad mpg, and the TQ wouldn't lock up, and the AC wouldn't cool. It would stay on any where from 10sec's to 10 miles then stop flashing and would drive normal again, but I would have to stop to get the idle to go back down. I pulled a 52 code.
Now it comes on just about every time I start the motor and stay on for any where from 2 to 20 miles of driving the go off again. then if I turn the truck off for 5-minutes or for a couple hours it will come back on again. but "usually" it won't come back on once it goes off. and now I pulled codes 52 & 42.
I pulled the ecm out and checked the contacts of the wiring & the prog, everything looked good, and nothing changed.
I drove it on a trip 300 miles each way and the light came on only when I would 1st start it and would not come on again.

I have been told it could be the ecm/prog going bad or the hall effect in the dist.
I do not know how or what to check. I don't want to buy a different ecm and it not fix it

Anyone have an idea what is it's problem, and how to check or fix it?

It's our only car right now, since our '93 s-10 Blazer quit, and I can't have it down, because of the wifes medical problems. and the closest auto store of any kind is 25 miles away.

Pat

 

Flashing CEL means your cat is suffering severe damage.

In my case I had to replace the spider injectors, it was leaking fuel into the exhaust system which was being ignited by the cat. I had to replace the cat too.

 

Sorry for the long time to reply.
If my cat is suffering severe damage, then why does the light go off. I drove it 300+ miles and it only came on for a minute or two at first, then never came on again? Then it did the same thing on the way back after I started it again.

I think it has to do with the dist. or ecu, but I don't know how or what to check to find out why it is doing it.

Pat

 

The light went out because the problem stopped. However the damage is done.

In my case it was due to a leaking spider injector assembly. I knew it was leaking, however I let it go, $300 was extremely tough to come by when your umnemployed, and the wife doesnt understand if it aint broken.

Since then I have replaced the spider injector assemble, and hte CAT. It got to the point the truck wouldnt run for crap, started out it wouldnt run wortha damn over 65, then 55, then 40mph. Mind you my flashing CEL never came on again, however the damage was done.

Pull the codes to find out where the problem lies. If it is the fuel injection system there wont be a code. The puter assumes it functions perfectely 100% of the time. No fuel, no run type of thing.

Eventually you may get a 02 code. Upstream sensor is different than downstream sensor or something along those lines.



Your call.

 

But with my problem, it runs great, it only runs poor when the light flashes, then it runs great again when it goes out, and it only comes on once each ti it runs, no matter how log it runs, but lately it's staying on longer. It started about a year ago, with a only couple of seconds, to now of some times a minute to 15-20 miles of it.
With your bad spider it ran bad all the time and was pumping/leaking the fuel wrong.

I did check the codes a few times. At first I got a 51 code, then later on, about 6months later about 2 months ago I got a 51 & a 42 code, and two days ago I pulled them again and only get a 51 code. Which says the prog or the ecu is going bad or bad ground, or weak power, which can also be the Hall Effect doing it also. I need to know how to check them so I know which is bad.

I don't believe it's my cat has anything to do with it.

Pat

 

A 1990 system does not check catalytic converter function. There is only one o2 sensor located upstream of the cat.

Flashing check engine light generally means stop driving and get service immediately. Code 51 indicates a problem with the MEM-CAL or PROM chip. If you can, look for a small cover on the ECM. Pull that cover off and look inside. There should be a chip in there. Make sure all contacts are ok, and that the chip has no burn marks. If you see nothing visually wrong with the ECM that can be corrected you'll probably have to replace the ECM.

You could probably get one from the junkyard, if you have one near you. Or if you know of someone with a 4.3 TBI anything, maybe you can get them to let you borrow an ECM just to test it out. A full size truck, S10 truck, Astro van. Make sure it is a TBI ecm

 

Ok, I have changed the ecm with another, when I took mine out, it looked good inside and out. The one I took out is a 1228062 (mine is a '90, 4.3 W/TBI, auto), the one I have in is a 1227747 which is from a Van with a 5.7 W/TBI, auto.

I put a ecm 1226867 from a '86 2.0 W/TBI, auto in and then changed it to the 1227747 It runs great, with either one, and no "check engine light" any more. but it acts like it has a bad TPS with both, but it didn't with the original ecm.
It does start hard at times (not always), like I need to pump the throttle to get it to catch and then it sounds like it is loaded up with gas, till it runs good, but it does not smoke like it's loaded up. It started doing that just before I changed the ecm's and still does.
I pulled codes again today and got a 4-4 & 5-1. I got the 5-1 before, but never the 4-4. I'm going to go and clear them, and see if they come back again!

Any idea's why I'm getting the 5-1 yet and why it runs like it has a bad TBS, mostly at take off?

Pat

 

I wouldn't run a PROM chip from a different engine. Programming is quite different between the applications you have listed.

44 - Oxygen sensor voltage was under 0.25 volts for 50 seconds of closed loop operation.
51 - PROM Error.

 

I was told it didn't matter what the engine size was. as long as it was TBI and an auto. I do not not know this, I was told it, and not from this forum.
I know that 51 means bad ecm or prom, but I was getting that from the oem ecm. but never got the 44.
Can I pull the chip out of the oem ecm and use that, or is the programming not in it? It was going to defalt mode all the time before, but ran good when it was not flashing the CEL. actualy it ran kinda good when it flashed, just no power.

Pat

 

The ECU itself can be swapped once the pinouts have been verified, but the PROM is different for each application. From what I have been able to find through google on the ECU part numbers, both of the ECU's themselves have the same pinouts.

I believe that both use the same PROM type (2732A) so you could try swapping the PROM from your 8062 ECU into the 7747. Hopefully the PROM wasn't the problem.

The 7747 is the ECU that many people swap to. Its a good ECU.