Gurus, hoping to get some technical guidance for a sick C4.

I'm trying to help out our club president with his 1994 LT1/A4 convertible with 68k miles. The car has been running great all summer. Just last week, the car started dying out on him, as he was driving. Pretty much as if someone had leaned over and shut the key off as the car was moving. **Edit**: The car does re-start after a few minutes of sitting. **Edit**

My initial thought was ignition control module. He replaced that but it continued to die out. We then thought perhaps the coil was flaky, so that was replaced yesterday, but after just 10 minutes of idling, it just shut off on its own again.

I took my fuel pressure guage over to his house yesterday morning, just to see how the fuel pressure situation was looking. He's pulling 45 psi at key-on, and holding a steady 40 psi at idle. Pressure also holds steady at 40 psi at engine shut-off. I'm thinking fuel pressure is likely ok.

He's not getting a SES light, but I haven't had an opportunity to scan it for any stored codes yet. According to his records, the Opti, plugs and wires were all replaced about three years ago.

I'm going to have him try the "dark garage" trick to see if he's seeing any sparks, but can anyone think of anything else we haven't considered?

Thanks much in advance!

Ron

Yea, codes are a must,Ron.
But an opti can act that way for a while without throwing one. This sounds like it happens frequently so there may be a code.

The dark garage thing is OK but bad wires usually just cause a miss.

Check the opti connections and the coil wire connections.

Check the F/P when it cuts off at idle.

Possible but doughtful - ECM ground.

Where did he get the replacement opti?

Also check the wiring to the ignition control module.

Matthew

Everything points to a bad ICM. That it runs and idles OK, but then shuts off like turning the key off sure sounds like an ICM. If it is missing and sputtering then I did not see that in your description. I would take the original ICM and the new one out and have them both tested.

I am with Matthew on this one... check the harnessing TO the ICM, too. Age, wear, oil deposits all conspire to mess up the harness...

Okay, a couple more clues here. Here's a snip from an e-mail the car's owner sent me last night...

"I hooked up the fuel pressure guage and we started the car. Pressure was good like when you were here. Shut off all lights and looked for sparks. I saw little flashes of light by the wires and coil but nothing really big. They would come and go, sort of like a lighting bugs but smaller flashes. I timed the start of the car and checked the temperature inside on the guage. The car shut off after 15 minutes and the temperature guage was 195 inside the car. The pressure guage was reading steady at 41 and when it shut off it went to 47 and then went down to 42 and stayed there."

So I think we can safely rule out a fuel system problem, at least up to the injectors. However, the "little flashes of light by the wires and coil" have me concerned. Could this possibly be a short somewhere that is causing the coil or ICM to overheat and temporarily fail?

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That's the #1 suspect area to check.

Matthew

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Yea, really.

There shouldn't be any flashes anywhere.
He needs to do this again and find out exactly where those flashes are and correct the problem.

The flashes are electricity going to ground. While this wouldn't kill the coil or wires, the ICM has electronics in it. The grounding (flashes) may have screwed up the new ICM, as mentioned, it needs to be tested.

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Actually, the original ICM was taken back to the parts store and tested out OK.

I think we're on to something here though.

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Yea, Ron.

No flashes anywhere, AND a spark can be a huge problem if there's a fuel leak.

Depending on age, I would say it is time for new wires.

Well relpaced the coil and the igition module. so thats fuel pump screen fuelpressure reg, coil ignition module. still dies out. whats left fuel filter and optispark. anybody. at wits end , thankyou.

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Before you do anything else, it's a must that you determine exactly where the flashes are coming from. You have to find out if they are coming from the coil wire, coil or ICM before you can do anything else.

Also a "must", you have to pull the codes, you can do it on the dash using just a paper clip.

I wouldn't spend any more money until you do the above.

How old are the plug wires? Miles on them?

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Bill, this guy is posting about a different car. He has a thread going about an 89 with an LT1, which has me confused.

not sure on the wire and plug miles. they were on the car when i bought it.after it died again the check engine light came on along with the batt light. and its a new battery. maybe alternater.clueless. gonna put OBD meter on it tomorrow. need a break before i throw something at it.

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OK, we'll get both squared away.

Italian1969 - Welcome aboard!

Are you a friend of screaming_conure? If so, are we talking about your car?

If not, please start a new thread and give us some more detail about your car. Trying to debug 2 cars at once is really hard... messages get crossed real easy.

well today is teardown day for my 96 vette. need to replace rotor and cap. its the only thing left to replace to keep it from dying out. replaced everything else. going to test the alternater while i have the belt off. im thinking i should get plugs and wires then all will be replaced. if this dont keep it from dying out i will have to have an accident and file an insurance claim. any input.

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Yep, I think we've been "cross-threaded" here.

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Welcome to the site. As Andy mentioned earlier, you really need to start a new thread. Include all the information on your car and the problem. This way we don't get confused trying to help two different people with different problems on the same message thread.

Matthew

An update on my guy's '94...

Stopped by his house yesterday in hopes of scanning for any stored codes. I have an Auto X-Ray OBD1 reader/scanner, and an Actron Pocket-Scan OBDII. As it turns out, I wasn't able to scan ANYTHING. I had forgotten that '94 was the year GM put a 16-pin interface on an OBDI system. My OBDI scanner didn't have the proper interface, and the Actron OBDII reader couldn't communicate with the ECM. Argh!

Will the paperclip trick work on a '94? I wasn't sure, so I didn't pursue it yesterday.

Also, the car's owner is off in search of a new Opti-to-coil wire. He removed it, and said it looked okay, but he decided to try replacing it just the same. If that still doesn't correct it, he's going to defer to his mechanic in hopes of trying to find out the source of the underhood light show.

On a 94-96 you can check the codes with a paper clip as follows:

You short pin "12" to pin "4" and turn the ignition switch to "On" without starting the engine.

The speedometer will display any codes using the same protocol as the 1990-1993 model but there are some changes in the designation for the modules plus additional modules are added:

Module "1" is still the CCM module.

Module "4" is now called the PCM module (Powertrain Control Module) because automatic transmission computer control was added to Engine Control Module in 1994.

Module 7 (on the 1996 model only) is the RTD module. (This is the Real Time Dampening module which replaced the Selective Ride Control module in 1996).

Module 9 is the ABS/ASR module number from 1994 through 1996.
Finally, Module "A", the DERM (Dynamic Energy Control Module --- (the air bag control module) will be requested to show any codes.

Just like the 1990-1993 display, you read the codes on the speedometer (big) and read the module number on the trip odometer (small).

A series of dashed lines for instance “ - - -“ indicates no more stored codes for that module.

A code showing as “C12” for the CCM module (module #1) means no codes are stored. So C12 is a good thing to see.

Again, you can cause the codes to repeat by turning the ignition off for five seconds and then back on.

Turn the ignition off and remove the short to restore normal operation.

To clear the codes,

1. With ignition "off" ground terminal #12 of the DLC (use bent paper clip to connect pin 4 to pin 12)

2. Turn ignition "on".

3. Press trip/odo button on the DIC until 1.7 appears in the trip
monitor area of the instrument cluster.

4. Press eng/met button on the DIC & hold until "---" appears in the
speedometer area of the cluster, this will clear CCM DTC'S.


To clear PCM/ECM codes do the following:


1. Press the trip reset button on the DIC until the desired system is displayed. In this case it will be 4.0.

2. Press trip/odo button on the DIC until the desired diagnostic mode(4.7) is displayed on the trip monitor area of the cluster.

3. Press & hold the eng/met button on the DIC until "---" is
displayed in the speedometer area of the cluster, this will clear PCM codes.


To clear ABS/ASR codes do the following:

Same as above but you’re looking for “9.7” on the trip odo

1994-1995: Diagnostic Trouble Codes
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.

I can't seem to copy & paste the pic of the connector but looking straignt at it, the pins are:

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16
Jump 4 & 12.

Thanks Bill! I'll pass this along to the car's owner, but I have a feeling he will be taking it in to have it checked out.

Ron

Another quick update...

The car's owner replaced the coil-to-Opti wire the other day. The car started and ran, but died again. However, he claimed that it ran much longer before it died. Before, temp would get to about 195 degrees when it would die, almost without fail. This time, the car idled a bit longer and got hotter before it died.

He let it sit for a few minutes and it restarted with no problems. This time, however, he let the car sit for about 30 minutes and it DID NOT DIE OUT. Temp went well into the 220-230 degree range. He even blipped the throttle a number of times during this period and the car continued to run. I was on the phone with him during most of this time and I could hear the car idling in the background. Sounded good. I was urging him to take it out and drive it, but he was short on time.

Haven't talked to him since, but I'm planning to head over to his house again today after work to do a resistance reading on his injectors and to try the paperclip trick to check for codes (thanks again Bill!).

I'm thinking we MAY have found the issue.

I'll update again later.

Ron

Well, back to the drawing board.

Stopped by the car owner's house yesterday after work. I did the paperclip trick and got a "C12" for module 1, meaning no codes. Module 4 had an H44, and module 9 had an H71 if memory serves correct. I don't think either of those historical codes pertain to the issue.

I also did injector resistance readings. Results as follows (cylinder number -resistance reading):

COLD = 1 -13.6, 2 -14.2, 3 -13.6, 4 -14.3, 5 -13.6, 6 -14.5, 7 -13.6, 8 -15.0

HOT = 1 -13.2, 2 -13.7, 3 -13.0, 4 -13.2, 5 -12.9, 6 -13.1, 7 -12.9, 8 -13.1

The car sat and idled for about 30 minutes, with a few blips of the throttle thrown in, to get the injectors hot. However, after 30 minutes it died out on its own, and we couldn't get it restarted (just cranked and cranked, but never fired). So, we just went ahead and took the hot readings. I noticed a couple of times when we blipped the throttle that the engine stumbled a bit when it was coming back down to idle. I also thought it was kind of strange that the resistance readings went DOWN or stayed the same on the hot injectors. I thought they would have gone up. He's still running the original Multecs. Even though they're old, I have serious doubts that the problem is injector related.

Anyway, the car's owner is taking it in to his mechanic Monday afternoon (assuming that it starts again for him). I really thought we had it with the new coil wire. I felt bad that I couldn't help get it sorted out.

I don't think it's the injectors.

The ohm readings going down makes sense, the slightly higher wire temps will have less resistance.

Remember, when checking injectors with an ohm meter, all you are checking is the coils, not the injector performance.
But this isn't his problem.

Did you clear the codes?

The H44 is may not be the problem BUT does need to be addressed. Both oxy sensors need to be replaced.

Tell the mechanic about the sensors. Note when the oxy sensor produces little or no voltage the ECM throws a code 44 AND kicks everything into "Open Loop".

Hey BillH. the H44 came from module 4 which is the Power Control Module. Would that make a difference? Does that still pertain to the O2 sensors?

And yes, I did clear the codes.

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Yea, Ron. I don't have the 94 FSM but I believe module 4 just had a name change because some auto trans things were added. It's basically like the 92-93 plus tha additions. So, DTC 44 in module 4 is the left oxy sensor, lean.

Just to put a period on this one, it turns out that it was in fact the Optispark. The car's owner took it to his mechanic and he was able to determine that it was the Opti that was failing. Not sure exactly how he did that, but a new MSD is in place and the car is running just fine now.

As a matter of fact, the car was driven 380 miles round-trip to Funfest at Effingham this past weekend without a single issue.

Great.

I luv my MSD, it has 15k on it now.

I am curious... did the mechanic change the opti AND the wires?

This does not sound like an opti failure. If it was, I would expect codes as it lost the ability to maintain either timing or fuel.

I think the smoking gun was the sparking off the coil wire. It is not uncommon for the wire the chaff on the waterpump and kill things...

For some reason, I feel that the mechanic saw an opportunity and ran with it. New wires, $50.00; new MSD opti, $500.00; installation profit, priceless.

Hey Andy,

All the mechanic did was change the Opti. The plug wires were replaced about three years ago by a different mechanic. However, the car's owner did replace just the coil wire himself during the time he and I were troubleshooting the problem. Changing the coil wire alone didn't fix the issue.

I don't know this mechanic myself, but he's been doing business with the car's owner for many years and they know each other well. I'd hate to think he would take advantage of a situation like this. I believe he only charged the car's owner $300.00 in labor to replace the Opti, which I think is a real fair price, and also let the owner source the part himself.

Good to have a resolution and good to know the car is running well now!