tttjump

What are signs that an ECM may be goign bad? 1987 corvette with 160k miles. ECM appears to be original.
I have an extra ECM from an 88 with a hypertech chip.
Can I swap and 88 ECM into and 87?
Can I swap the chip from an 87 ECM into and 88 ECM?

The 88 is the back up ECM, so they above questions are just in case I have to swap to make it home scenario.

The 87 ECM appears to be stock. service number 1227165 ABTF
867771 M612115164
The chip in the 87 numbers on it, 16035006 8620
along with a sticker that say Delco ABTF 0735

The 88 ECM is a remanufactured one. With an AC Delco sticker
GM # 88999194
ACD # 88999194
LC21 4907 06041
GR. 3. 670 CG ECSM

Hypertech chip pn is 158332

3D-Aircrew

Code 41 generated lead me to think either bad ECM or PROM. It turned out to be the PROM but I replaced the ECM first before settleing for another aftermarket hypertech prom since the stock ones weren't available.

What I was getting was a bad miss with the CEL setting the code at first intermittentaly then all the time.

onedef92

It varies. Typically the car will start and run, but stalls or seems to not idle right.

If so, is the check engine light illuminated, on intermittently, or all the time?

If so, what are the MIL diagnosis codes? Try pulling ECM and looking and smelling for burns. Have your ECM tested to be sure it is functioning properly. If the ECM is bad, have it repaired or replaced with known remand or new unit.

If ECM is OK, then follow the error codes it gives, and check the appropriate malfunction (i.e.: check engine light coded you had bad oxygen sensor, try unplugging it and restarting car to see if any change in running or the MIL.

If no change, try putting a known good used unit in, or buy new unit.

Have ECM scanned in car by authorized tech with proper scan tools specific to application (only after installing or verifying you have a good ECM). Most manufactures have specific tools to there equipment even though there are many scan tools that can do basic diagnosis. This scan should show what elements are giving you the problems.

There are some ways to check error codes without scan tool. Refer to your owner's manual for specific applications.

tttjump

I get the code 32 and 42 about twice a month and a no start about once a month.

I wait about 30 minutes and the car will start.

I will look into it more when the SES light flashes again.

3D-Aircrew

Don't use the wrong part number ECM. I'm not sure what bad it could do but it can't be good. Also your hypertech chip is for:
1988 Corvette 350 Tpi Auto W/Od Thermomaster. (Ca emmisions)
The OD is only for the shift indicator on the dash and the thermomaster turns the fans on at a cooler temp. I wouldn't use it either unless hypertech said so.

What symptoms are you getting?

Some things you can try first before buying new ecm or prom is to check grounds, unplug and reseat your PROM, unplug and reseat the two connectors on the ECM.

3D-Aircrew

32 has to do with the EGR and I don't think it's related to your code41 which is a cylinder select error.... which in my case ended up being a bad prom.

I couldn't even find a used prom for an 86 ... that why I had to plop down 2 bills for a hypertech.

tttjump

Other than the code 32 and 42 The car runs fine, just passed smog.
I get a no start about once a month, wait 30 minutes and car starts and run fines.

Normally the SES light will flash in the morning upon initially starting the car. The next restart the light goes off.

I clear the codes and wait for the light to flash again. Which is about two weeks. It is always the same two codes or just the code 32. Never the code 42 by itself.

3D-Aircrew

That's funny that the codes are linked like that...code 32 can be complicated but the 41 is not that bad...I believe the FSM is the same for your 87:

http://members.shaw.ca/corvette86/Code%2041.pdf

http://members.shaw.ca/corvette86/Code%2032.pdf

(Courtesy of Agent86)

MBDiagMan

Will it allow you to draw codes?

tttjump

I listed code 41 by mistake. I just checked my notes and it is code 32 an 42.
I justed started the car and the SES light came on. code 32 is stored.
Code 42 is not stored this time around.

3D-Aircrew

http://members.shaw.ca/corvette86/Code%2042.pdf

rick lambert

I really doubt it's your ECM. Most times when the ECM is heading south it'll run pig rich. But you may want to check and clean the connections.

An as far as the 32 goes, sounds like the EGR switch. Ceap fix, and 95% of the time when 32 is thrown...that's what it is.

BTW, I don't know anyone who can check the ECM, but if you know someone with a scanner you could check the whole system. I use a laptop, and Craig Moates connection. Forget the program, but it was a free download. Cheap investment, used laptop and connection around $200.

cousinit99

Hey Rick, I know this thread is practically ancient, but since you seem to know what a bad ECM behaves like, how does this sound?

I have to pump the gas (as if it were carb'ed) just to get it to start anymore. If I crank it without my foot on the gas, 1 in every 6 or 7 cylinders will fire, giving you the indication that it's trying to start, but basically, the thing just does not want to start without the throttle plate open. Once and a while, it will start right up, but not often, and when it does, it's totally random.

When I finally do get it started, it idles by itself, but misses once every 2 or 3 seconds. Then, as soon as I press on the gas, it doesn't rev up, it stumbles hard, but the slower and lighter I step on the gas, the less it stumbles. If I press on the gas sharply to about 25% throttle, it will most definitely choke itself out and die. It behaves this same way when the TPS is unplugged, but even so, the TPS is brand new and verified operational via scan tool (key on voltage and throttle angle response).

Here's a quick video that shows what it takes just to start it, and what pressing on the gas to about 10% and 20% does:





It actually started somewhat easier that time. Usually, it only fires one in every 6 or 7 cylinders to start out with..

I have an Innovate MTX-L as you can see, so at idle, I can tell it maintains a somewhat consistent AFR, but every time I press on the gas, it goes "pig rich" like you mentioned Rick. The whole fuel system is practically brand new. New plugs, wires, pump, filter, injectors, regulator.. Pressure is 47 PSI with the vacuum line disconnected, injectors test good for resistance, and the prom tune accounts for the 30Lbs/hr SVOs. Also, I have reverted to a known good prom tune from a year and a half ago (when no issues were present).

I've now been through 3 different optisparks. It's not an optispark issue, or a wiring issue. But there are bad voltages present in the high-res opti circuit (purple w/white wire). The voltage in that circuit is not consistent and above 4 volts, it's variable and jumps around anywhere from 0.9v to 2.0v. I have cleaned all the block, chassis, and bell housing grounds, and I ran 4 new leads directly from the green ECM connector to the optispark pigtail on the side of the intake. It's not a wiring issue.

And get this, when I pull the Airbag fuse (yes, the airbag fuse) the jumpiness in the hi-res opti circuit goes away. With that fuse pulled, the hi-res voltage is approximately the same as the low-res voltage (optispark connected, key on).

What say you? Anyone besides Rick is more than welcome to chime in, too. His comment just leads me to believe that he's had some experience in this particular area, that's all..

mixalive

I had similar symptoms recently. It started out as an intermittent issue but progressed to all the time. Turned out my MSD coil had cracked. I installed my old factory coil and problem solved. It had cracked around the base of where the connector connects to. Worth a try..

cousinit99

Thanks for the suggestion, mix..

guno89

My damn car would not idle properly it constantly stalled. I replaced the IAC it ran great for 2 weeks problem started again. Swapped out the ECM after going through the flowcharts and help form the forum. The car has been running like a champ for about a year now.

cousinit99

Did you live in an area that rains a lot, or has high humidity when you first started having those problems? Did you ever find out why your ECM went bad?

tunedport85inject

hi guys i want enter this thread since a friend of mine (he has an 88') is having a lot of troubles with his ECM.It's an intermittent issue when it happen he lost completely electronic advance.At first i was thinking about a bad ESC module.To ceck it we changed his ESC with mine with no luck.After a lot of cecking we realized it was a bad contact between eprom and ECM connector.forcing his hypertech back and forth.When he has full contact the car runs great with full ESC functionality.Since this contact between eprom and ECM was poor and erratic he decided to order a remanifactured one and now he has the same issue,it seems like he has burned his new ECM so i'm now thinking about a short somewhere that fried the ECM,but again i know there is a fuse to protect ECM...any ideas is apreciated since now he is afraid to put a new one and fry it again...thanks guys

mixalive

I had my ECM rebuilt a couple of years ago. I just wanted to share its symptoms. I noticed my car would die at idle sometime. Then one day the car would not rev beyond 2500RPM with both fans on all the time and the A/C would not blow cold. I seem to remember also having a SES light on. I assume I was in a "limp mode". So I sent the ECM out to a company for rebuild. When I reinstalled the ECM, all issues had been corrected.
I would like to note that the company I used went out of business and my lifetime warranty was crap.

Cliff Harris

When my ECM went bad I would be driving down the street and the engine would just cut off like the key had been turned off. A few seconds later it would start running again.

There are two numbers for the 1227165 ECMs because there is a modification that is done (they put a new number sticker on it after the modification). I have one with an added white wire. From what I could tell by tracing out the circuit, it appears to be related to the MAP sensor, which only applies to '89 Corvettes with this ECM.