Question… I have been searching through wires under the dash and in engine compartment for any shorts or damage, so far haven’t found anything significant. I’m not sure what the likelihood is my ECM is faulty…But I happen to have a spare. It’s in my running ‘91. Would it be a bad idea to pull it, swap PROMs, and put it in this car as a test? I’m just hesitant to take the chance of damaging a known good one, but if I’m careful… Would it cause headaches with regard to losing any learned settings upon swapping it back again? Or anything else I’m not thinking of? ECM part numbers for 90 and 91 are the same, I confirmed.

 

good idea do it.

are the proms different btwn yrs?

 

You might try putting the suspect one in the good runner and see if you have the same symptoms in it. That way if there is a problem with the wiring/sensors in the 90 you won't be taking a chance with the known good one. I did much the same with my two 92's to verify that the ECM that I had rebuilt by SIA wasn't still having issues. I think the setting are all in the prom so that shouldn't be a problem.

 

Very good point - will try this today.

 

I have notice at car shows they are installing plug and run LS engines, easy fit and mate to the transmission.

 

This is an exact duplicate of post #4 in this thread. What’s the deal?

 

Just a quick update about electrical issues. After putting the questionable ECM into the running car, it exhibited the same issue, so confirmed the ECM (or possibly the prom) has issues. Ordered an ECM from O'Reilly (remanufactured Cardone 77-7727) and when it came, I plugged it all in and DEAD. It wasn't communicating with the CCM at all (no SES light). At first I didn't think it was likely I had a repeat bad ECM so I tested and re-tested all the power and ground lines, but all connections tested fine. Then I put the old one back in, and it went back to intermittent faults again (at least not completely dead). I noticed the prom chip was pretty hard to insert into the new ECM so there must be something wrong with that connector. Bad luck!

So I ordered another ECM from Amazon (fastest delivery option) and installed it for round two - this time it appears to work fine, SES light is on as expected. First turn of the key, the engine cranked but wouldn't fire. Next turn of the key, and NOTHING. Wouldn't even crank. But the ECM still seemed fine so I grounded A and B of the ALDL connector and it spit out a code 46 - VATS!!

To make a long story short, I could not see any obvious problems with the wiring under the dash, tried a few more times to start it, wiggled some wires, and eventually it fired right up. I am guessing this will continue to be an intermittent issue until I get to the root of it.

Anyway, I did manage to take the car for its first actual drive. Could tell very quickly that front shocks are shot (new ones now on order). Transmission seems to work ok. Engine runs fine mostly, but I did get some hesitation and missing when applying throttle. I am guessing this could be related to vacuum line disconnects - I need to go through and replace them all with fresh lines and connect those that I capped at the plenum. Continuous problem solving! Not that I expected perfection. But I'm a bit unsure exactly what to expect from a new engine in its first few miles. Should it run really well right away? I was able to connect it to TunerPro and watch the data flow a bit. It seemed everything was within normal parameters.

I am somewhat uncomfortable with operating temperature. On my short run with it, it crept up to 220 and I'm not sure if the fan came on - that was just as I started going at higher speed and air flow dropped temp back down to 210 or so. I know due to all the discussions about operating temperature that these cars run in the 200-230 range pretty frequently - that doesn't mean I like it, especially for a new engine! The A/C isn't working yet so I'm curious if I get it going what the temperature will settle on with the fan running. If it still doesn't run cooler I think I will focus on the radiator. The car had an aftermarket aluminum radiator put in at some point, but I'm not sure how long ago nor whether it was a decent quality one. I put a new 2-row Champion in my '91 last year and it has been running at a consistent 205 degrees ever since.

So I still have a large smattering of issues to chase down. Aside from the things already listed I need to install a catalytic converter (this car is currently straight piped so it won't pass inspection), change transmission pan gasket/filter (there's a small leak), brake pads, and possibly rotors. A true C$ project for sure. At least I got lucky with decent wheels and tires!

 

Regarding your operating temps, I'm thinking that given the temps you are seeing in the Tucson area that it isn't out of the norm. Have you checked to see if the rad isn't clogged up with debris? Was there any sludge in the cooling system when you took everything apart? Verifying that you are getting good air and coolant flow would be my 1st step before I'd start shelling out money for a new rad.
Is it possible that your VATS is the root of your intermittent no start problems? I'm not that well versed in that system but have seen on here where it has caused a lot of members all kinds of grief.
On the other hand, it seems you are making good progress and that 1st good shakedown cruise had to be a good feeling!

 

Agreed - great to have it on the road! Even better, it was so grimy that last night I had a hard time seeing out of it - so I dedicated this evening to giving it a good wash - first in at least 5 years! It looks SO much better.




With regard to the radiator, I haven’t taken the cover off to inspect more closely but it looks pretty clean from below. I flushed it with the hose before hooking it up to the new engine and other than some rust residue that washed out pretty quick it was pretty clean. I’m betting it was one of the last things done before the old engine bit the dust.

VATS…. I’m just going to pretend there’s no VATS problem for now and maybe something magical will cure it. It started fine today.

 

When you hooked everything up on the cooling front, these cars take a while to purge the air out. Unless you employed some tricks. I know u did an engine swap so perhaps u have not fully purged the air. As long as the overflow system is working properly, and there is fluid you have put in the overflow, then the system will purge the air out as pressure burps on heatup, then as it cools the vacuum will bring coolant back in to replace the void from the gas that left.

The leaves, twigs, plastic bags, that get in the rad shroud is astounding. Sometimes a good scrub with a long bristled brush on the condenser is enough to keep the temps down.