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94 Seville
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Discussion Starter #1
The Northstar in my 94 Seville (175k miles) has been almost flawless over the last 100k miles. There'd been no sign of any problem before starting her up last night. She immediately began missing randomly on all cylinders; reminding me of a vacuum leak in a carburated engine. As I forged home, she continued missing and idling very rough. I had to keep my foot on the gas to keep her running at idle. A handfull of times the idle surged up to 2500 (without my help), afterwhich she'd run good for 15-20 seconds. Part way home the dash LED display displayed, "Traction Control Disabled". The missing and roughness got worse the more I drove. By the time I got her home, it was difficult to keep her running.

This morning I started her up (problem persists) and got the following CURRENT codes out of her: P023 and A047. From the list of codes on this site, my P023 code looks interesting. The description of that code on this web site says, "Electronic Spark Timing (EST) Signal problem [EGR]".
After lunch I'm going out to look for vacuum leaks. Any ideas or input would be greatly appreciated.
 

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White Diamond '03 DHS (with DTS floor shift)
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Have you cleaned the EGR and rodded out the "mouse holes" in the intake?
 

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94 Seville
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Discussion Starter #4
Ranger, I've located and removed the EGR. Nothing jumps out at me as looking like it needs to be cleaned. The piston in the valve moves freely and the other hole in the valve (a hair broader than the one with the piston), though coated with exhaust soot is open. Both holes in the intake are open as well and don't seem to have any more than a thin build up of exhaust soot. What kind of cleaning procedure should I do? Or does she sound clean enough?

Also, if anyone has any idea of what voltages and currents are applied to the valve, I have access to a variety of power supplies to test the valve and can test it at work tomorrow.

Thanks, Jeff
 

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White Diamond '03 DHS (with DTS floor shift)
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Everything sounds good. I have never had a '93/'94 but my understanding is when you remove the intake cover there are "mouse holes" that need to be rodded out. That seems to be the clog point . Do a search for "mouse holes". You should come up with a lot of reading.
 

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Your ignition module is bad, or related wiring or connectors aren't connecting properly.

I'd get some "electronic contact cleaner" from a parts store, remove the connectors, and spray them down good... let everything dry, and reinstall the connectors. See if that doesn't fix it (probably won't, but it wouldn't hurt to try).

After that, I'd replace the ignition module with one from a junkyard ($40).
 

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85 Eldo Biarritz
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Yeah, this sounds more like Ignition Mod. Related than EGR. Unless EGR was stuck full open.
If "mouse holes" were plugged up, then exhaust gasses would have problem getting to the intake chamber (even with the EGR valve open). That would not make the car want to stall. It is overabundance of exhaust gasses in the intake which make the engine want to stall.

Well, this could also be related to an electrical EGR problem (keeping the EGR valve open). Too bad that the codes are so vague.

Peteski
 

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I don't know who added the "[EGR]" to the end of the text there, but the code is for an EST error. The computer is trying to control the timing, but the ICM is not listening. This could be due to a break in a wire, or a bad ICM. Since you say it's barely running and it happened suddenly, I'm putting money on the ICM.
 

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94 Seville
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Discussion Starter #9
Thanks for the input guys.

Just to make sure that I understand exactly which part you're talking about; it's the four coils mounted on the rear valve cover that the plug wires run to. Is that correct?
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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The ICM is the part that the four coil packs plug into. The plug wires are connected to the packs and the packs are connected to the ICM. You have the correct location.

The fuel filter is located just under the car, behind the back driver's side door, before the rear wheel well.
 

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jss said:
Thanks for the input guys.

Just to make sure that I understand exactly which part you're talking about; it's the four coils mounted on the rear valve cover that the plug wires run to. Is that correct?
that's correct. The coils each have 2 bolts holding them on to the ICM, in case you need to move them over to the new one. Order is important to keep the numbers painted on them correct.

The ICM has 4 plugs on it, I believe. Try removing and spraying those with the electrical contact cleaner/wiggling them around/etc. Make sure they're dry before plugging them back in. Maybe a bit of grime is giving you some contact problems, but more than likely the module is bad.
 

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2000 Dev, 94 FW (crushed), 96 FW Limo (sold), 95 SLS (sold)
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I've read many similar posts and the cause is generally coil packs. Be sure to post findings when repaired. Good Luck.
 

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94 Seville
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Discussion Starter #15
Guys, I've finally freed up some time to run down another ignition module. I rounded up enough neighbors to push her up into the garage and I replaced the ignition module. It made no difference. Problems are identical to what they were with the previous ignition module.

If anyone has any other ideas, I'd like to hear them.

Thanks, Jeff
 

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The code description says "Electronic Spark Timing signal problem." Could this be a crank or cam position sensor issue? ewill3rd, do you have any thoughts on this one?
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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Your code P023 was set because the PCM did not detect any ignition pulses. When this happened, the PCM disabled the egr solenoid and disabled spark timing control. Instead, the engine will start and run on base timing.

I would check all the wiring to and around the ICM, like Eldorado1 said.

By the way, A047 is low refrigerant in your a/c system.
 

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ugh... I wrote this huge post, and then I closed the window. :banghead:

Lets try this again.

Code P023 will set under either of the two following conditions:
1) 4x reference pulses are being recieved by the PCM and the bypass line is low, and the PCM detects pulses on the ignition control line. This could be caused by the bypass line shorted to voltage, or a faulty ignition control module.

2) 4x reference pulses are being received by the PCM and the bypass line is high, and the PCM does not detect a signal on the ignition control line. This could be caused by an open or a shorted to ground ignition control line or bypass line open or shorted to gruond.

Both of these lines lead to the "big" connector on the ICM, next to the "5/2" ignition coil. Start checking for corrosion, melted wires, etc...
 

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94 Seville
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Discussion Starter #19
Gentlemen,

A thanks all around for the input. I can tell you that all connectors on the ignition module are clean. I've just gotten home from work and we're loading up the kids and presents and "off to grandma's house we go". When we get back Monday, I'll start at the ICM and work my way back as far as possible unpluging and cleaning connectors.

If anyone knows of an on-line wiring diagram for the 94 Seville's ignition, I should be able to probe and test shorts and opens as you've suggested.

I hope you all have a very Merry Christmas.

Thanks again, Jeff
 
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