Fifty8bowty

This is a VIN code P car. When I'm driving along it's like you turn the key off and in a split second right back on again. Or sitting and idling the car will just quit, but will fire right up again. I do get a code 36 which I know can be the opti, but I replaced that about 3 years ago with an MSD unit. Not very many miles on it since. I checked the voltage to the opti and that checked out, but since this is intermittent that might not mean much. There are also other symptoms. The ABS/ASR and INFL RESTlights come on and go off occasionally although everything seems to be working normal. I also cannot pull the codes with a Tech 1 or code scanner, but it will work with the paperclip method. I cleaned the battery terminals and the 2 grounds to the frame right by the battery. I checked the flat copper wire ground near the oil filter and it is tight. I'm leaning toward replacing the ECM with so many odd things happening at once, but I thought I'd see if anyone here had some thoughts on it. Thanks!
Ty

c4_4ya

What codes are you getting? Jump A to G for all codes ; 1 is CCM 4 is ECM 9 is EBCM. If you jump A to B, it just flashes the ECM codes via the CEL. I had a fun time with mine doing crazy stuff, and had CCM code 41- turned out to be a shorted serial data line. Then when that was fixed, had an ECM code 41 which appears to have been a loose ICM connector.

Fifty8bowty

Thanks C4. I will try that first and post the results. Probably won't get to it until Saturday though. I appreciate your help.

Fifty8bowty

Hi C4,
I finally got a chance to pull those codes and here's what I got:
Mod 1: C12=no codes
Mod 4: H32= EGR problem
H36= dist problem (which I had before)
Mod 9: H62= high resistance pass key
H72=LCD circuit open or shorted to ground.
H83= this one through me as it's not listed in my Helms manual. Any ideas? I ran the codes twice so I'm pretty sure that's it.

I'm also wondering if any of these would cause the symptom I described in my initial post where the car kills at an idle or dies out momentarily at highway speeds. I will start whittling away at these issues.
Thanks!
Ty

c4_4ya

The only code I think would be suspect with your car dying after its already running is 36. I would clear all codes, and try to recreate the problem. If the car dies again, immediately pull the codes. It could also be that the connector(s) for the opti are getting loose and causing an intermittent stall, had this happen with my icm driver connector which made me think I kept frying ICMs.

Fifty8bowty

I agree. I did find the EGR problem. It turned out to be a cracked hose. I've been chasing the code 36 for a while. The opti is an MSD unit I put in about 3 years ago. I have probably driven this car less than 2k miles since. I will recheck all connections and see what I find. The MSD unit is hard wired so the first connection is about midway along the right side of the intake. Do you know any cheaper alternatives to the backprobing tools they recommend? Those things are so danged expensive, but they also recommend using the correct tool to avoid damaging the connectors. Thanks again! I really appreciate your help!

Ty

c4_4ya

Can't help you on the tool side; what are you trying to test for? Opti is the one electrical problem I haven't had with my 92 yet lol

Drew1Down

my FSM shows a code 36 to be a Data Strobe Circuit (open or shorted to ground) that have to do with the cluster display. Try the wiggle test around and under your dash

Fifty8bowty

Well I thought to trace this code 36 I may have to back probe and wiggle any connections involved. It could be the opti is faulty again but I need to check all the other options before I tackle that dog again. One other issue I need to address is the Tech 1 won't read from the DLC port. But I can get them by grounding the A terminal. FSM tells me it's a problem with the 800 circuit or possibly the ECM. I'll keep chasing the gremlins in this car.

Fifty8bowty

Drew, actually the code 36 was from the ECM module which is opti related. I think the code 36 you saw is from the CCM module. I'll probably still be wiggling wires, just in another area.

c4_4ya

Check for short to ground on the G plug on the aldl connector, it's the tan wire. Also check it for short to B+. Either of those conditions should trip CCM code 41, and the FSM documents the testing procedure. Could again be a loose connector.

Fifty8bowty

Will do. I have some wire tracing to do for sure. Thanks for all your help C4.

leesvet

Harness grounds.

C4 wire harness are famous for cracked insulation causing shorts, cross over shorting..The grounds on a plastic car are more important than the power source. See the ground bundle of 14 & 16ga wires on the block/bell housing.

Inside the cabin, the trunk from the thru connector is usually ok, its the branch lines that get broken or damaged because they lay on things and get abused with each repair. Its undersized wire so it breaks easily.

Fifty8bowty

Looks like I have my work cut out for me. Well, one wire at a time I will get it solved. Thanks for the tip.

JM95

I had similar issues with my 95 LT-1 Coupe. First, I found that the threads on the battery terminals wire stripped to the point that I could create the engine drop out by tapping the connector. Repaired by using longer stainless steel bolt on both terminals. With the onset of warm weather the drop out reappeared. I replaced the Ignition Module (ICM) above the coil. After trying several BW I installed a genuine A C Delco and no more problems. You might try a replacemnt wire harness from connector on passenger side of intake to the Optispark. Available from EFI Connectors, Erie , PA. Failure in this harness or the Weather-Tite terminal will generate an error 36. I am assuming the engine achieves closed loop witout a problem, NO MISS at change over open loop to closed loop. This happens in the 145 to 160 temperature range and is generally in the O2 sensor, EGR circuit or small vacum leak on my car (had leaking check valves in air bypass loop).

leesvet

Start where everyone else finds problems...at the bundle around/near the oil filter. On the block or a bellhousing bolt.

Thats 5 critical ground wires. Next, those wires enter the harness trunk on the firewall right behind/under the wiper motor. This IS a very fragile area of the harness. If you want to dive in, do so at your own risk. I say that knowing whats in there and the fact that there WILL be something worthy of repair,...
The harness splices shown on the FSM drawings are cheesey at best. A simple crimp on with some black tape. Thats it. As these wires age the exposed wire gets brittle and corroded. It breaks. Without good ground paths the ECM is blind and will use the cal-paks to substitute for the missing or out of spec data. High resistence (dirty connection)in a circuit often means radical swings in engine operation...or just a misfire.

This collection of grounds that all enter the harness trunk line are all these cheap simple splices. Once you get into the harness and peel back the sleeve, you will see what I mean. Mine was so rotten that I had a misfire that could not be pinned to anything...I eventually found the rotten wire splices and chopped out most of the driver side injection harness and soldered in new wire at the harness. Problem solved. I realized how serious the problem was when I saw that the misfire would move from one cyl to another...that side only. It was getting "cross-over" signals from the broken insulation.
The other side never had an issue and the wire is like it came from a different car. Good shape.
If you look and see some insulation starting to crack and split or peel off the wire, then its time to dig deeper.
I don't think you have a jumper post (only certain yr models) behind the battery where all the "always hot" wires originate and go to fusable links...but DO trace the origins of these HOT ALWAYS circuits and make sure the contacts are clean.

When something like a computer managed system depends on things like reference voltage (low voltage signals) and variable resistence, the wire matters !
Every connection matters, every inch. Like she said...

Because the resistence values change over the years with dirty connections and corroded wire, That makes pushing a delicate signal thru very important to the performance of the engine. In the case of unexplained misfiring or poor performance you have to go thru and clean and tighten all these connections to be sure they are transmitting the signals to the ECM to and from sensors that the car requires.


Dirty connections come down to a loss of control and management of the engine. Its a hassle but the results can be dramatic. I've suffered misfiring that came as quickly as it went as I discovered a dirty connection somewhere. I recently had this happen when I got in a hurry and stacked several hot wires on the jumper pole without cleaning..bolted them in dirty and even wet with oil...The car misfired and pinged like The timing was 30 degrees advanced.
Went back and used a small wire wheel in the dremmel to clean and shine all the connection tabs and the post, bolted it up and the problem was GONE...all from the jumper post and power wires being dirty. The more complicated these cars get, the easier it is to muck up the operation....

TIP:
whenever you pull a plug off or apart, after cleaning with the wire brush or whatever means, I apply some silicone grease to the plug and seals to keep water and dirt out. So far this has provided yrs of sealed plug-ins.
Good luck..you'll figer it out.

Fifty8bowty

The ICM is another thing I thought of but I will check all my wiring first. It achieves closed loop without anything noticeable happening. When it has killed at idle or cutout at highway speed, it has happened when both cold or warmed up.

Fifty8bowty

Thanks for the tips Lee. I do need to located that bundle on the bellhousing, among the other connections. I will be on the lookout for any marginal looking wires too. Is there a good way to clean the connectors that plug together without damaging them? Like spray tuner cleaner or mechanically cleaning them? I have been using my Dremel too. It is really slick for cleaning those hard to get at bolt on grounds. When you use silicone to seal a plug I assume you need to be careful not to get it in the wire contact area? What about using di-electric grease? Thanks Again for all your help.

c4_4ya

Have you noticed whether it happens over rough patches/bumps? If so I would really suspect loose connectors or grounds.

Fifty8bowty

No actually just sitting at a stoplight it will kill, or running down the highway on a smooth road it will shutdown for just a second and then pick right back up again. It never dies completely at highway speed, only for a second or two.