Need help from the guru's

BillC · 09-03-2009, 04:33 PM

Hi all, in a past thread I talked about my XR8 missing. the suggestion was to put new spark plug leads. I put MSD leads on but the car is still missing. i am running NGK iridium plugs that have been in for about 20,000 Ks prior to these symptoms. The symptons are:

Starts fine, drives fine. Good economy (well what you would expect from an XR8)

But after a drive for about 30 minutes the car will miss. When I say miss it loses power for two or three short bursts. Its like the car hic ups. It does not feel like the leads are breaking down because I have felt this before. It mainly does it at low revs. Doing a U turn for example but not all the time and not necessarily turning. Then it might not do it again for another 30 minutes.

One thing I noticed when I tried to change the throttle position sensor with my mates Au 6. I pulled it out and when I put it back on I positioned it incorrectly and it gave the same hic up almost every time you drive off from a full stop. When I positioned it correctly it stopped doing it at take off but it has that same hic up every 30 minutes or so.

I am thinking I may have a dead spot on the TPS.

Could this give me those hic ups at a certain rev point ?

I would like to find one and swap it for a day to see if that is the problem before I go and buy on. I am not convinced this is the problem. I wish I knew somebody else with an XR8. Au 6 cylinders look the same but they have a different plug.

I took it to the local mechanic and of course he could find nothing wrong with it. It did not do it for him.

Any help or ideas would be appreciated

RG · 09-03-2009, 04:42 PM

I'm going for a coil pack fault. They are a known issue that causes a miss and can be worsened by rising under bonnet temps.

gtfpv · 09-03-2009, 04:48 PM

definately coil pack , as RUSSELL . says . tell tale symptom is . only when it's warm .

BillC · 10-03-2009, 10:38 AM

Thanks guys, I have a spare one at home. I will give that a go.

RG · 10-03-2009, 10:52 AM

The ones the leads plug onto front and centre of the engine?

BillC · 10-03-2009, 11:29 AM

I bought a coil pack quite a while ago when I did a valve spring. Obviously I tried it and it didn't fix the problem. I have changed it before. I guess it will be try one and if it does not fix it I will try the other one. I hope this is the problem. You guys seem quite sure its the issue so its worth a try particularly as I have one sitting at home.

I will let you know how it goes.

**Stav** · 10-03-2009, 03:27 PM

Its the ngk plugs.

BillC · 10-03-2009, 05:03 PM

I will try the coil pack first. If its still doing it after that I will get some new spark plugs.

**Peuty** · 10-03-2009, 05:16 PM

When you say "the" coil pack, I hope you mean two coil packs?

**Stav** · 10-03-2009, 06:56 PM

Get bosch plugs...

RG · 10-03-2009, 07:13 PM

Quote:

Originally Posted by Stav

Get bosch plugs...

Why would you say that? I've only ever run NGK plugs in mine and I've never had a problem.

**Stav** · 10-03-2009, 09:34 PM

Because NGK dont make good quality ceramic insulators.They crack too easily.They suck.

RG · 10-03-2009, 09:41 PM

Quote:

Originally Posted by Stav

Because NGK dont make good quality ceramic insulators.They crack too easily.They suck.

Never had one crack on mine, not even going into no.5 cyl.

**Stav** · 10-03-2009, 10:00 PM

For a guy that wanted the best out of my car I removed and reinstalled plugs like no tommorow.I can say I never cracked 1 bosch plug but 90% of the ngks.

RG · 10-03-2009, 10:07 PM

Quote:

Originally Posted by Stav

For a guy that wanted the best out of my car I removed and reinstalled plugs like no tommorow.I can say I never cracked 1 bosch plug but 90% of the ngks.

Sorry Stav but I'm going to have to say in has to be either poor luck or bad technique.

I've used NGK plugs for years on both the AU and the EL and I have never once cracked a plug. I change them in the AU regularly and I did so with the EL too.

**Stav** · 10-03-2009, 10:17 PM

I have to say poor quality mate. When the chips are down ..quality counts.Also the iridiums produce a more powerful spark but not as fat as normal plugs so they tend to be great when fairly new but seem to misfire alot more than normal plugs as they age.

**Stav** · 10-03-2009, 10:18 PM

Ill video tape 6 ngks and post it here to prove my point. A slip of the spark plug remover shouldnt crack the insulator but ngks do.

BillC · 11-03-2009, 11:26 AM

Hi all, I know the 8 has 2 coild packs.

I swapped the left one last night and the problem is still there. i then swapped the right one and problem still there.

I honestly dont think is a misfiring problem though.

Its like the engin cuts out for a split second. like its not getting a signal to to fire the plugs. seems to only happen at low revs. I can get the car to do it most of the time now just by taking off real slow. As the car is slowly going up the rev range the engin cuts out for half a second then its fine. Sometimes it will doing in second gear. (cars an auto).

This fault is driving me nuts.

RG · 11-03-2009, 11:44 AM

If you have a fault in both, which is highly likely, then changing one at a time won't show it. These Motorcraft coil packs generally only last 80k before they start having faults.

Have you cleaned your MAF?

blueoval · 11-03-2009, 12:07 PM

Im gonna go out on a limb and say its the ecu.

I had what you had BillC on my EB XR8. Changed ecu's and the problem stopped. If you can get ya hands on an ecu to test it, do it.

BillC · 11-03-2009, 12:45 PM

I hope its not the ecu. $$$$$ I just went to the local mechanic and I have booked an appointment tomorrow. He will hook up his test gear and we will take it for a drive. Hopefully I can reproduce the symptons for him and this may point to the problem.

This may also be relevant, About when this problem started happening I had a squeek coming from the front of the motor. See a previous post. Anyway the mechanic said it turned out to be a dry shaft where the crank angle sensor is. I am not sure exactly as I have never seen it. Anyway he pulled it out and applied greese which fixed the squeek. Now I have the engin cutting out. I suspect this is related.

I just asked the mechanic if he moved the crank angle sensor and he said he didn't but said they may have gotten some greese in or on the sensor or even where the plug fits in. He was unsure why it is only a problem at low revs.

I will see how it goes tomorrow and let you know.

**Stav** · 11-03-2009, 08:38 PM

Check the ego sensors as well

BillC · 12-03-2009, 10:39 AM

The good news is that the car played up when I took it to the mechanic this morning. He hooked the diagnostic computer to the car and it showed a fault in the can angle sensor. He cleared it then we went for a drive and the fauld happened a couple of times and each time the cam angle sensor lost signal.

At least we are getting closer.

blueoval · 12-03-2009, 10:53 AM

Thats a positive diagnosis Bill. Keep onto it mate.

BillC · 12-03-2009, 05:17 PM

For those following the story so far. Replaced the Cam angle sensor. Diagnosis says no fault. $107 for the sensor and 30 minutes labour = $150 odd dollars.

Drove from the mechanic shop back to work (about 600 meters) so far so good.

I will let you know in a couple of days if this was the problem. Fingers crossed.

BOTTLEDUP · 12-03-2009, 05:46 PM

Good to hear that things are heading in the right direction. As I scrolled down and read the symptoms I was thinking cam/crank sensor fault, for it to cut everything like that.

Keep us updated!

BillC · 17-03-2009, 10:56 AM

Good news all round. Cam angle sensor fixed the problem and the car is running all sweet again. Its just like a bought one.

blueoval · 17-03-2009, 01:39 PM

Quote:

Originally Posted by BillC

Good news all round. Cam angle sensor fixed the problem and the car is running all sweet again. Its just like a bought one.

Good to hear Bill. Enjoy