: Misfire and coils



jsjag
08-21-05, 09:05 PM
Just got a 95 De Ville with the NS engine. We were driving it from CA to PA and in North Platt, Nebraske (@1,000 miles or so into trip) a misfire started. MPG started going down.

Upon arriving in Ohio to visit my sister I decided to take a look at the problem. I saw that the owner had a new coil tower and wires replaced 4.5 years ago. Once it was dark out I decided to check out any arcing of the wires. Well I saw a light show on the left side of the coil tower. The next day I changed plug wires and again, the night time I looked and still had arching. My brother in law has no ohm meter and because the car is new I had no idea what the primary and secondary redings should be so today I took each coil to a parts store to get checked. Each coil was within spec.

Am I correct, the coils sit on top of an ECU? The invoice from the previous owner shows he spent $900 at the dealer for a new tower and plug wires. IS there a known problem with the ECU / coil tower going bad on these cars?

Today, Sunday, was the final day of our two weeks on the road, my son is sick with a 103 fever and no time to spend waiting for a mechanic (don't even know one in OH) and I will have to drive the final 700 mile leg with a misfire. The car started out the trip running sooooooo smooth,

JS

sts96
08-21-05, 11:25 PM
The coil can check ok and still have a carbon track or crackthat will short the HV, a replacement is easy to get at most parts houses.
sounds like help for your son is far more important. best wishes sts96

jsjag
08-22-05, 08:10 AM
Thanks for the reply. I'm back home and I'll go buy 4 today and replace them. The coils are only $20 each at Auto Zone. I hope I didn't do any damage to the engine. I doubt it because there weren't any back firing of the engine nor any check engine light. For many miles I thought I had bought bad gas outside Laramie WY. I needed gas, it was the only station and it was out on the range. You had to cross one of those in ground cattle gaurds to get to the station. Saw some interesting people at that station. :)

N0DIH
08-22-05, 02:15 PM
Looking at night is a good way to check for electricity going where it shouldn't.

When you ohm the coils, make sure they are at temp, not cold. The coils expand and contract, so you will get false readings.

Ranger
08-22-05, 03:27 PM
"Am I correct, the coils sit on top of the ECU?"

The coils sit on top of the ICM (ignition control module)

jsjag
08-22-05, 07:30 PM
"Am I correct, the coils sit on top of the ECU?"

The coils sit on top of the ICM (ignition control module)

AH...I used the wrong terminology. On my Jag the ign control mod is a bit more easily accessible.

I replaced all coils today but still have a misfire and it is probably still tracking on my wires. I talked with my Jag parts guy and he said it could very well be the wires I bought are not up to the task. A mechanic I know said the same thing. I removed the wires I bought and will return them.

I guess when you have 100,000 volts firing and wires firing on input and exhaust the wires take a beating. My Jag guy said that some of the Audi's and Mercedes are famous for eating wires.

I think I like the days of a rotor and one coil.

Ranger
08-22-05, 10:33 PM
I have heard other complain about aftermarket wires. When mine developed a misfire, right after the fuel rail (recall) replacement (a common phenomenon). I used OEM wires and solved the problem.

jsjag
08-23-05, 09:32 AM
Ouch!!!!! The dealer wants $198 for a set of wires for the 4.6. The dealer parts guy was a bit confused because wires for the 4.9 were only $70. I'm guessing that the non-NS engine isn't direct ignition coil stuff and has the good ole rotor.

There is a TSB out on the wire/plug/boot/arcing/carbon tracing problem. I guess GM's cure was a set of wires for $198. I'll get a set of Megnacor's before spending the dealers inflated price of $198.

My NAPA parts store has a set for $83. He said he has sold 3 sets this year and no problems were reported with the wire set.

When you say OEM did you mean the $198 set?

jsjag
08-23-05, 09:43 AM
I have heard other complain about aftermarket wires. When mine developed a misfire, right after the fuel rail (recall) replacement (a common phenomenon). I used OEM wires and solved the problem.

At the moment I'm not tooooo thrilled with the DeVille's quirk. Apparently carbon tracking/arcing/misfires was substantial enough to issue a TSB. I posted my thoughts about it on one of the other forums. Below is my current frustrated feeling about it:

On 8/15/05 we picked up a 95 De Ville Concours in CA and drove it to PA. It ran fine until we hit Nebraska and then a misfire started. New wires haven't fixed it and new coils didn't fix it.

I am in PA now and talked with one of my mechanics yesterday. He ran a TSB on the 95 De Ville Concours and almost 300 TSB's appeared. Stopped at the one discussing wires/plugs/carbon tracking and misfires. The TSB says to use spark plug AC-929 (ribless insulator). It also mentions wires (GM part of course). The TSB states, "The new AC 929 spark plug and boot design significantly reduces carbon tracking and reduces engine misfire." Reduces? How about eliminates???? The TSB also states, "The boots contain FHC grease as a lubricant. If silicone type lubricants are added to FHC coated boots, carbon tracking of spark plugs may occur." Well isn't that just ducky. Many of the wires you buy already have a small amount of silicone rubbed applied to the boots.


I guess I now see why the PO spent 0ver $900 at the dealer for wires and coils. UNREAL! Minor tune up items costing $900.

IMHO the wiring loom on this car is made for carbon tracking and or arcing. The wires to the rear plugs are longer than needed and create a 90 degree bend, the wires going to the front tubes lay on top the manifold tubes and are held down on the metal tubes by the plastic cover.

For the past 15 years I've driven Jags and never need to pay for dealer only items like plugs or wires. The after market parts from my parts guy in Idaho work very well, the local parts stores also work for my Jag parts.

$900 for wires and coils. Give me a physical break! The engineers went way out of their way on this car to cement dealer only maintenance. I'm not thrilled with the maintenance part of the car.


It is a nice car to ride in, has a lot of power but I'm not sure I want to own a car that I can't even do a plug/wire job without dealer assistance.

Ranger
08-23-05, 11:35 AM
Ouch!!!!! The dealer wants $198 for a set of wires for the 4.6. The dealer parts guy was a bit confused because wires for the 4.9 were only $70. I'm guessing that the non-NS engine isn't direct ignition coil stuff and has the good ole rotor.

There is a TSB out on the wire/plug/boot/arcing/carbon tracing problem. I guess GM's cure was a set of wires for $198. I'll get a set of Megnacor's before spending the dealers inflated price of $198.

My NAPA parts store has a set for $83. He said he has sold 3 sets this year and no problems were reported with the wire set.

When you say OEM did you mean the $198 set?
Yes, OEM, (Original Equipment Manufacture (A/C Delco)). NEVER pay dealers price. I think I paid about $120 at http://www.rockauto.com. You might also try http://www.gmpartsdirect.com.

eldorado1
08-23-05, 06:53 PM
Don't use partsdirect if you want the parts anytime this month. I've had good experiences with rockauto.