I've had my Delteq for a little over a year now and about every thousnad miles or so it eats one of the plugs on the drivers side of the engine. I don't know which one. I change all four and it goes away. I've got AS&M headers and I'm using some of the stock plug wire terminal end protectors to avoid burnt wires. I haven't burnt any wires but I was never too impressed with the wires supplied by Delteq and have been consittering changing them.

The miss starts out only under hard acceleration but eventually ends up missing contunously. I change the plugs on the drivers side and it's fine for a thousand miles or so. I was running NGK TR55 plugs but switched to TR5. I think the TR55 plugs lasted longer. I've got the Delteq under radiator mount kit.

Any Ideas are appreciated. This is starting to get anoying.

On the plus side, I can change the drivers side plugs in about 8 minutes.

 

I believe this is what you're looking for http://web.camaross.com/forums/showt...ngk+spark+plug
Seems the higher output of the ignition system kills the plugs

 

Now I'm real confused.

I don't think I'm having a problem with bad plugs. The same one goes bad each time. I've inspected the removed plugs and never found a carbon trail or other obvious damage. I'm not even positive the Delteq has anything to do with this. I've had it on the car nearly as long as I've had the car on the road.

 

I have had a similar problem but it was with the plug comming loose in the head, not saying this is your problem but maybe next time before replacing see if you can wiggle the plugs before removing. When mine would do it the plug was still more than finger tight(as much finger as you can get on them) but would sort of rock back and forth if that makes any sence.

 

Check the fitting of the coil packs on the bracket. Mine came loose and Deltec sent a new plate with better threads for the coil mounts. Made a difference. I was getting an occasional miss and it was a loose coil. Also, put some dilectric grease on the terminals for the coils. It helps, especially if there is water. I don't trust the radiator mount due to vibration and filthy environment and put mine on top of my intake manifold.

 

Have you ever measured the internal resistance of the plug
(or all 4 plugs) to see if it was "different" than a healthy plug?

The description is a bit confusing:

 

None of the plugs are loose.

I'll have to check the coils.

I'm just assuming it's the same plug. Over the last year I've changed the plugs on the drivers side about 4 times. Each time I do it's cures it for a while. I've only chnaged the passenger side plugs once when I changed from TR55s to TR5s. I'll have to change plugs one at a time and see if I can figure out which one is missing.

 

Do any of them look fouled? I assume not since you didn't say so. Why don't you do one of a few things to find out which one is not firing. I like to let the engine cool down then start it up and immediately check the primary temps to find the one that is missing. But if you don't have an infrared thermometer you can do it a few other ways. You can pull the plug wire or the injector clip off and see which cylinder doesn't change the way the engine is running when it is removed.

I find it odd that the one that is bad is not fouled. Perhaps a compression test while the engine is hot would be appropriate. If there is one that is fouled, it could be a leaky injector or a bad valve causing compression to drop and not fire correctly. It could be an injector that is restricted causing a lean misfire and the plug then could look white not fouled.

If compression is good, move the injector from the cylinder with the bad plug and see if the plug problem follows the injector.

 

Problem is the miss only happens under load. Initailly it will take a heavy load. Like putting it in 6th at 50mph and flooring it. After a hundred miles or so the car will barely pull it's self in 5th without missing. It dosn't miss at idle though so I can't pull injector plugs or use a temp sensor to find it. Also, because I've got a Delteq and two cylinders share the same coil, one bad plug causes two cylinders to miss. Guess I'll have to replace one plug at a time to find it.

A compression check is a PITA but a good idea.

 

Explain to me why one bad plug causes 2 cylinders to miss????? don't you have that backwards, you mean 1 bad coil causes 2 plugs to miss?

That explains a lot. You are using the wasted spark type coils and if I remember correctly, the driver for those is a module under the coils. If that is the case, they suck donkey water. Those modules go bad all the time causing crappy running. Might be something to consider. Try swapping one at a time from side to side. You could also try heating them up individually with a hair dryer to see if any of them crap out when you get just too hot to touch comfortable with the bare hand.

Where the hell did I get the phrase Donkey water from

 

Exact thing my 3.8 was doing. Replaced the coils and all is good.

 

In a "waste spark" system, the secondary current path is a series circuit that is made up of the coil secondary and both spark plugs and the spark plug wires to those spark plugs.

The current in a series circuit is the same throughout the entire series circuit. If any component (like one spark plug) in that series circuit becomes defective in a way that limits the current in that series circuit, it affects all the components (including the other spark plug) in that series circuit.

If spark plug A and spark plug B are two spark plugs in series in a "waste spark" system and spark plug A opens up in a way to prevent current flow through it and the current has no path around spark plug A (because the gap is too large), spark plug B will not fire either.

Tom Piper

 

I've got a few spare coils lying around. Good idea.

 

Oooooo I stand (or sit) corrected. You are very right. I love it, that is very VERY interesting. I have never bothered to look at the V6 portion of the shop manual. In there is vague information about what you speaking about with regard to waste spark ignition. Well I dug it out last night and went back to the 3.4L from 94 and sure enough, when you check one spark plug for spark, your supposed to short the companion plug wire to ground. This makes sure you aren't seeing the effect of a bad companion plug and incorrectly assume the one you're looking at is bad.

My hat's off to you sir Thanks for that information.

Dave

 

I have a Delteq system too, and I have never had a problem -- but, I don't put that many miles on it.

However, thinking about this problem, here is the only thing I can think of that could be related to the Delteq:
The coils for the Northstar coil pak are somewhat potent.
So, if you are using resistor plugs, maybe the current created by the Northstar coils is enough to heat the resistors in the plugs and eventually cause them to fail.
A good way to find out would be to use resistor plug wires without the resistor plugs -- I don't suggest running non-resistor plug wires with non-resistor plugs.
It would be interesting to know if the Northstar engine uses resistor plugs, or if the plugs are some kind of heavy duty resistance plug.

Please keep us informed.

Tom Piper