Ignition

[WOO5IE]

Hi,
I am trying to chase a long standing issue of the car being very hesitant when hot, Car is great except when getting hot after a time in slow moving traffic.

Tonight I checked the car in the dark to see if I could see any HT leakage. I have recently installed a new Bosch coil

The only spark I could see was where the low tension wires connect to the coil. i could also hear a crack of arcing as well.
The main problem is that the engine/power Seems very hesitant when the car is very warm and was apparent on the old coil as well

I did change most of the ignition components last year but all at once . Coil,leads,dizzy cap ,ignition module rotor arm. This didn't seem to clear the problem so I changed them all back to the original components.

This doesn't pose much of a problem to me as I don't often drive in heavy traffic and only low miles per annum.

So the main question is should I be able to see any sparking at the top of the coil.I suspect not

Thanks

Trev

[bobfather]

A couple of thoughts:

It could be running rich, that would show itself more as engine temperature increases

The ECU temperature sender could be faulty, showing an artificially low temperature. That would cause rich running at high engine temperatures

[TV8]

if you have a meter, I would check the resistance of all the plug extenders. Also, an infra red temp reader on the same place on each exhaust manifold will tell you if one or more cylinders are hotter/cooler than the others.

[WOO5IE]

Hi Guys,

Thanks for the suggestions, I have already recently changed the ecu temp sensor .
There have been a few posts on here recently re plug extender failures and their unreliability and not being able to get decent replacements.

I don't think it is a mixture issue as the car doesn't run hot unless in very slow moving or not moving traffic , it has also very recently Passed the MOT and emission tests. I was going to order some of the heat shrouds so that I can eliminate the extenders which you can get quite cheaply . I took the car out today and got caught in a short jam and the car started playing up. It Felt like a HT leakage problem hence the check in the dark. I will probably order some heat shrouds anyway but when I saw the Sparks at the top of the coil I thought that I would ask here if you thought that was normal. It is on the low tension connectors so I don't think it is right.
I will try the temp reader on each cylinder over the next few days and I have cleaned the low tension connectors and I will put the original coil back on

Trev

[freddytin]

The spark appears to be taking the path of least resistance, which in this case is the connection on the coil.

Personally I would ensure the nose of the coil is free from dirt , like new .
Secondly look for high resistance on the leads, particularly end connectors are corrosion free and firmly home .
The plug gaps should not have excessive gaps and mixture shouldn't be super lean.

And no, the coil should not be tracking out .

Edit to add..The problem of tracking ignition systems is always going to be worsened with a hot engine due to resistance increasing as the mixture gets leaner.
Sorry for the disjointed post, having problems with coordination

Edited by freddytin on Thursday 12th November 23:12

[QBee]

Driving down to London last Sunday (A1all the way) I commented to my passenger that I suspected I had a misfire. Nothing major, just felt slightly off. Cold morning, so temp gauge was at 65 as usual.
In the London, traffic built up, temp gauge moved smartly up to 90, car felt like a bag of nails, and was popping and banging the moment I changed gear or took my foot off the gas, impressing the lads on the pavement. Yup, I had a misfire.

Parked, went into the car show, having dropped my EBay digital laser thermometer onto the driver's seat ready for our return.

On our return we fired up the engine and started testing temps. Pretty soon spotted the number 6 exhaust was 150 degrees cooler, switched off, removed the extender, switched on, all fine.......but still got a misfire. Number 3 turned out to be the culprit. Removed extender, car now running on all 8.

My extenders were replaced in March. That's six that have now failed. I have purchased a used set of extenders off another Chim owner, and a set of thermal socks off a Scottish rambling club . When they all arrive I will see which I prefer.

[Dr Mike Oxgreen]

Ditch the extenders, QBee - you know it makes sense!

Same to the OP.

[WOO5IE]

Dr Mike Oxgreen said:

Ditch the extenders, QBee - you know it makes sense!

Same to the OP.

Hi Doc, have now ordered some heat socks but will removing the extenders that maybe resistive cause any issues.Spark or interference?

Thanks all for your replies

Trev

[QBee]

WOO5IE said:

Hi Doc, have now ordered some heat socks but will removing the extenders that maybe resistive cause any issues.Spark or interference?

Thanks all for your replies

Trev

Possibly, suck and see.
If it does, simply swap your plugs for a nice new set with an R in the product description, eg NGK BPR6ES, or NGK BPR6EIX, or there is an NGK BPR7ES or similar plug, I am sure.

[blitzracing]

Just a bit of theory on the HT voltages- the peak voltage at the output of the coil will depend on the total resistance seen between the coil and ground via the spark plug gap. Basically the coil voltage will continue to rise until it finds a path to ground - but no more than about 30kv as this is the peak the coil can kick out. The resistance of the path will constantly change as the rotor arm rotates and puts the voltage down different HT leads. Its perfectly possible that say 7 leads / extenders / plug caps are fine, but then when one is open circuit the HT voltage will rise much higher than normal on the bad line, so the now elevated coil output will short to the nearest ground- ie the LT side of the coil.

[Dr Mike Oxgreen]

WOO5IE said:

Hi Doc, have now ordered some heat socks but will removing the extenders that maybe resistive cause any issues.Spark or interference?

When I got rid of my extenders, that was before I got the resistive NGK BPR6EIX plugs - I was running B7ECS. The engine ran beautifully, although I've no idea if it was creating interference. There was, however, probably enough resistance in the Lucas HT leads I had previously fitted.

[WOO5IE]

Thanks Blitz and Doc,

The HT theory sounds exactly what is happening but the proof in the pudding will be when I remove the extenders.
I just had another drive and checked when the car was very hot and I could see and hear the HT arcing to the low tension connectors on the coil.

The leads are suppressed Magnacors so may well not need resistive plugs.

I did check the temps of each cylinder just by the exhaust manifold of each cylinder but was a bit inconclusive as there was not a definite temp difference but as the arming is intermittent this may not be the best way to determine what extender it or two is faulty.

Remove the lot I think is the best policy

Thanks all again. I will update when extenders removed and heat sleeves fitted

Trev

Edited by WOO5IE on Friday 13th November 16:40