92 $stealth$

bladerunner13 · 09-15-2007, 04:46 PM

I copied this post from someone else and it describes my problem exactly, anybody know how to cure this!

my 6 cylinder Stealth mostly runs on 4 cylinders. (the middle 2 from coil pack dont spark) I have tried a new module 3 times. ( the little black thing under the coil pack) i think its actual name is a power transistor?? the first one worked for 2 months then started acting up again. and I tried a used coil pack from ebay, worked for one day. Every once in a while when I first start it, it runs on all 6, then goes to 4 again after about 2 - 3 miles, when it goes to 4, the check engine light goes on and the idle goes way down. took the ecu out and it looks clean

Thanks in advance

**qldit** · 09-15-2007, 08:09 PM

Good Morning bladerunner13, I am not familiar with that vehicle but from my general experience find that those kinds of problems can be caused by a faulty spark-plug lead.

What I suspect happens is that the developed high voltage seeks a path to complete it's circuit, and if any high resistive path exists (due to a defective lead or by having a lead disconnected for any reason) can reflect to the coil driving circuit and damage the driver or internally arc within the coil windings damaging them and then cause load problems for the driver circuit.

Transistors commonly operate perfectly when cold but begin breaking down when they get hot.
This used to be called a "walking wounded" problem where the integrity of the transistor is affected and it's switching ability lost when hot.
(It's molecular structure alters)

Some modules need to be mounted with heat transfer compound under them and this was another factor often contributing to these kinds of problems.

I actually prefer to obtain spare parts from Auto wrecking places because quite often the generic replacement items are not as reliable.

In your case I would suggest replacing the sparkplug leads and the sparkplugs (or at least checking plug gaps) and also obtaining a suitable spare part for the coilpak, confirm whether these should be mounted with heat transfer compound and work appropriately.

As a point of interest, never disconnect a sparkplug lead to do any tests. If you do need to do a spark test, mount another sparkplug conveniently on the engine, cable tied to a lift point or something like that, and connect the sparkpug lead to it before cranking etc. This ensures no problem can be caused.

In the old days it was OK to disconnect a spark lead and simply hold it near the engine to check spark, those days are gone!

Others will have different ideas.

Cheers, qldit.

bladerunner13 · 09-15-2007, 08:45 PM

Hi qldit, thanks for your reply. I appreciate it and the obvious knowledge you have. I'll change my plug leads, which is a pain on this engine as you have to take the manifold off to get at the back three. Can you recommend any particular brand? You mention the coil driving circuit, do you think I could have damaged the coil itself or some other part? There is a "transistor", I think, mounted to the coil pack mounting bracket, I suppose that could be damaged as well. I'm not very good with electrical parts so I better go buy a tester and do some learning.

Thanks again for your input.

**qldit** · 09-16-2007, 05:39 AM

Good Evening bladerunner13, under the circumstance where there has been a multiple repeated failure I would suspect there has been a possible internal problem in the coil pack that is affecting those drive modules.

These kinds of things can really be a domino effect where a problem spark plug lead possibly affects the coil pack internally and that then affects the drive circuit.

In view of the expense, reliability and downtime considerations I would be inclined to fix it with a "blanket fix" that is where you throw a blanket over all the components that could cause that problem and replace everything underneath! It saves a lot of time and effort in the long run and avoids the domino problem.

As mentioned I am not familiar with that particular vehicle, but that is how I treat those kinds of problems.

Spark plug leads should be periodically replaced as a routine every couple of years.

I can't suggest any particular items, usually we have a "roundel" at the auto supermarket where you select the leads by length one by one of different types.
Generally they are all soft plastic conductive material in the centres these days, but that material does deteriorate over time and flexing cycles.

Be careful to only disconnect one lead at a time if you decide to replace them, it is easy to forget which lead went where, a nice little drawing of "which is which" may help.

When and if you select leads like this choose carefully to ensure the best length matches are made, there is nothing worse than too longer leads flexing in space!

Gee, I am not impressed at having to take the manifold off there! That sounds like pretty poor engineering design.
Those kinds of things deter proper procedural maintenance and promote these kinds of problem scenarios.

Cheers, qldit.

bladerunner13 · 09-16-2007, 09:16 AM

Good morning, yep, I like the blanket fix idea. I already had the manifold off once to change the plugs and I should have did the wires at the same time, doh! That is a poor design as far as maintenance goes but I should be able to do it in an hour this time.

There are all kinds of wires including ceramic now, 8mm or 8.5 mm. I'll get the specs on them as I don't want to be changing wires too often.

Thanks for your help, much appreciated. Have a great day!

bladerunner13 · 09-17-2007, 07:12 PM

Well its not the plugs or the coils. Got me stumped. Time to find a buyer before I end up in the poor house! Got to perservere.

**qldit** · 09-17-2007, 07:48 PM

Good Morning bladerunner13, Are you getting spark to those two cylinders?

Cheers, qldit.

bladerunner13 · 09-17-2007, 07:56 PM

Evening,

If I do it doesn't last for long, new plug wires today. Could it be the crank sensor? They only cost $950 bucks in Canada.

**qldit** · 09-17-2007, 08:59 PM

G'day bladerunner13, generally the crank sensor only senses rotation I would be doubtful that will be your problem.

Can you possibly arrange to read any computer codes that may be present?

Cheers, qldit.

bladerunner13 · 09-17-2007, 09:05 PM

I'll see if I can find what the mechanic wrote down. I know the computer was telling him coils and something to do with the camshaft or crank sensor, something like that.

**qldit** · 09-17-2007, 09:47 PM

G'day, "camshaft" sounds interesting.

Cheers, qldit.

09-15-2007, 04:46 PM	#1 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	92 $stealth$ I copied this post from someone else and it describes my problem exactly, anybody know how to cure this! my 6 cylinder Stealth mostly runs on 4 cylinders. (the middle 2 from coil pack dont spark) I have tried a new module 3 times. ( the little black thing under the coil pack) i think its actual name is a power transistor?? the first one worked for 2 months then started acting up again. and I tried a used coil pack from ebay, worked for one day. Every once in a while when I first start it, it runs on all 6, then goes to 4 again after about 2 - 3 miles, when it goes to 4, the check engine light goes on and the idle goes way down. took the ecu out and it looks clean Thanks in advance

09-15-2007, 08:09 PM	#2 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 92 $stealth$ Good Morning bladerunner13, I am not familiar with that vehicle but from my general experience find that those kinds of problems can be caused by a faulty spark-plug lead. What I suspect happens is that the developed high voltage seeks a path to complete it's circuit, and if any high resistive path exists (due to a defective lead or by having a lead disconnected for any reason) can reflect to the coil driving circuit and damage the driver or internally arc within the coil windings damaging them and then cause load problems for the driver circuit. Transistors commonly operate perfectly when cold but begin breaking down when they get hot. This used to be called a "walking wounded" problem where the integrity of the transistor is affected and it's switching ability lost when hot. (It's molecular structure alters) Some modules need to be mounted with heat transfer compound under them and this was another factor often contributing to these kinds of problems. I actually prefer to obtain spare parts from Auto wrecking places because quite often the generic replacement items are not as reliable. In your case I would suggest replacing the sparkplug leads and the sparkplugs (or at least checking plug gaps) and also obtaining a suitable spare part for the coilpak, confirm whether these should be mounted with heat transfer compound and work appropriately. As a point of interest, never disconnect a sparkplug lead to do any tests. If you do need to do a spark test, mount another sparkplug conveniently on the engine, cable tied to a lift point or something like that, and connect the sparkpug lead to it before cranking etc. This ensures no problem can be caused. In the old days it was OK to disconnect a spark lead and simply hold it near the engine to check spark, those days are gone! Others will have different ideas. Cheers, qldit.

09-15-2007, 08:45 PM	#3 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	Re: 92 $stealth$ Hi qldit, thanks for your reply. I appreciate it and the obvious knowledge you have. I'll change my plug leads, which is a pain on this engine as you have to take the manifold off to get at the back three. Can you recommend any particular brand? You mention the coil driving circuit, do you think I could have damaged the coil itself or some other part? There is a "transistor", I think, mounted to the coil pack mounting bracket, I suppose that could be damaged as well. I'm not very good with electrical parts so I better go buy a tester and do some learning. Thanks again for your input.

09-16-2007, 05:39 AM	#4 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 92 $stealth$ Good Evening bladerunner13, under the circumstance where there has been a multiple repeated failure I would suspect there has been a possible internal problem in the coil pack that is affecting those drive modules. These kinds of things can really be a domino effect where a problem spark plug lead possibly affects the coil pack internally and that then affects the drive circuit. In view of the expense, reliability and downtime considerations I would be inclined to fix it with a "blanket fix" that is where you throw a blanket over all the components that could cause that problem and replace everything underneath! It saves a lot of time and effort in the long run and avoids the domino problem. As mentioned I am not familiar with that particular vehicle, but that is how I treat those kinds of problems. Spark plug leads should be periodically replaced as a routine every couple of years. I can't suggest any particular items, usually we have a "roundel" at the auto supermarket where you select the leads by length one by one of different types. Generally they are all soft plastic conductive material in the centres these days, but that material does deteriorate over time and flexing cycles. Be careful to only disconnect one lead at a time if you decide to replace them, it is easy to forget which lead went where, a nice little drawing of "which is which" may help. When and if you select leads like this choose carefully to ensure the best length matches are made, there is nothing worse than too longer leads flexing in space! Gee, I am not impressed at having to take the manifold off there! That sounds like pretty poor engineering design. Those kinds of things deter proper procedural maintenance and promote these kinds of problem scenarios. Cheers, qldit. Last edited by qldit; 09-16-2007 at 05:44 AM.

09-16-2007, 09:16 AM	#5 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	Re: 92 $stealth$ Good morning, yep, I like the blanket fix idea. I already had the manifold off once to change the plugs and I should have did the wires at the same time, doh! That is a poor design as far as maintenance goes but I should be able to do it in an hour this time. There are all kinds of wires including ceramic now, 8mm or 8.5 mm. I'll get the specs on them as I don't want to be changing wires too often. Thanks for your help, much appreciated. Have a great day!

09-17-2007, 07:12 PM	#6 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	Re: 92 $stealth$ Well its not the plugs or the coils. Got me stumped. Time to find a buyer before I end up in the poor house! Got to perservere.

09-17-2007, 07:48 PM	#7 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 92 $stealth$ Good Morning bladerunner13, Are you getting spark to those two cylinders? Cheers, qldit.

09-17-2007, 07:56 PM	#8 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	Re: 92 $stealth$ Evening, If I do it doesn't last for long, new plug wires today. Could it be the crank sensor? They only cost $950 bucks in Canada.

09-17-2007, 08:59 PM	#9 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 92 $stealth$ G'day bladerunner13, generally the crank sensor only senses rotation I would be doubtful that will be your problem. Can you possibly arrange to read any computer codes that may be present? Cheers, qldit.

09-17-2007, 09:05 PM	#10 (permalink)
bladerunner13 Registered User Join Date: Sep 2007 Posts: 6 OS: xp	Re: 92 $stealth$ I'll see if I can find what the mechanic wrote down. I know the computer was telling him coils and something to do with the camshaft or crank sensor, something like that.

09-17-2007, 09:47 PM	#11 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 92 $stealth$ G'day, "camshaft" sounds interesting. Cheers, qldit.