My car is an '86 with a '90 engine setup. I have an intermittent problem where the engine will buck and stall with the check engine light on. I checked the codes today and it is setting 43. I also noticed that when this code is active that the radiator cooling fan will run with the key on, engine off. This does not happen if the code is not active and the car is running normally. When the check engine light is off the car runs great! Any ideas what could be causing this?

 

code 43 is a electronic spark control circuit (ESC) code. I think the knock sensor is in that circuit. It could be a number of things, either its sensing a lot of spark knock or its a shorted or open circuit.

 

Where is the knock sensor and how do I check it?

 

Also, if the engine is acting up the check engine light will blink randomly with the key on, engine off. I guess it's somehow related. Could a loose/bad PROM cause this?

 

OK I checked everything I could find in that circuit and everything looks ok. As a last dicth effort I pulled the ECM down to check the PROM. PROM was tight. I removed it and replaced it with another PROM that came with the car. The car ran great! I brought it home, changed back to the PROM that was originally in the car. It also ran great... I tried wiggle testing all the wires at the ECM with the engine idling, no check engine light, no stalling. I tried tapping the ecm with the handle of my 1/4 drive ratchet. The car sputters and the engine light comes on. Does this mean bad ECM? Anything else I could check? How much are they new/rebuilt? Any ideas where to find one?

 

Must be a loose connection in the ECM

90 setup means its a 730 SD

Find any GM car with the 730 ECM and swap your MEMCAL over. Easy ones are the 90-92 Fbody V6's as noone wants them

 

Like a junk yard part? How can I tell a 730 SD ECM from other types? Are the connectors the same? I assume the MEMCAL is the rectangle that clips in under the removable cover in the ECM? Sorry to ask so many questions but this is my first experience with ECM's in cars.

 

Yes, junkyards are full of good parts for quite a bit cheaper

730 is the last 3 digits of the ECM service number which should be stuck on the outside of the unit

Yes, the whole snap in piece is the MEMCAL. Inside the MEMCAL is the PROM. Its easier to swap the whole unit and since yours works fine, theres no reason not to

 

Well now I'm confused, I was poking around on the boards and reading up about my problem when I noticed that the 730 ECMs did not look like mine. I went out and checked my ECM (defintiely rebuilt) and the number on it is 7-7165. I guess it's a 165 ECM because the car definitely has a MAF sensor. The car is an '86 and the guy who sold it to me said that he swapped the setup from a '90 into it. Did they make MAF setups in '90? or was I deceived?

 

Either he lied or you have a 90 engine controlled by an 86 harness/ECM

 

Well... at least I figured it out before I went searching through the junkyard! Are these ECMs available on the 6 cyl cars also or are they more difficult to find?

 

165 ECMs are common

I dont remember disassembling any older V6's but the ECM may match up like the newer 730's. I really dont know

I do know that the majority of the ECMs sold on this site are 165's