Not running on all 8.

[Tri2Tri]

This has been bugging me since I have got the car back on the road over the last few weeks. The engine sounds like it is only running on 7 cylinders and not the full 8. The exhaust is smelly so there is a fueling issue somewhere. Plugs/leads have been checked and all are firing fine but it just dont sound quite right. It has been mentioned that the cam may be on its way out causing this but is there anything else I could check out before going down the road of cam change? As the car was in a right state when I salvaged it, I would imagine it has never had a cam change. 4.0 1996 serp engine.

[jojackson4]

Try a proven disy cap and roter arm
The new ones are st

[phillpot]

Pull plug lead off one at a time with engine running, see which one has no effect?


Laser temperature reader on header pipes, one should be a lot cooler if not firing?

[blitzracing]

On old trick is to run the engine, then get a cable tie and press it on each exhaust header so it melts- or more to the point its unlikely to melt on a header of the cylinder thats not firing so you can see the difference.

[Tri2Tri]

Thats the wierd thing as all ehaust outlets are running the same temperature, it does not look like the same cylinder on each cycle if that makes sense? I did use new after market dizzy cap and rotor so first up I will change these out for the original stuff then see how it runs then. All other ignition items are new,,,leads/plugs/coil/alternator. Ignition amp is still original item though. Once running over 3k revs the engine it pulls well. This is more noticable at idle or low revs.

[jojackson4]

Ing timing ?
Advance / retard

[Trevor450]

Mine had an intermittent misfire last year. It was the plug extenders.

[Tri2Tri]

I removed the rusty plug extenders once I changed out the leads/plugs. I bought some fire/heat proof plug socks instead and binned the extenders which work a treat. Right then, original fitment dizzy cap and rotor to be purchased then timming checked. I will report back once done.

[AV8]

Could also be the coil beginning to pack in.

[Tri2Tri]

I must admit I went for shiny blingy items as i had just cleaned up the engine bay so the new coil was a cheaper shiny lucas item. I will start by the dizzy cap and rotor first then go for a timming check up after that a bosche coil if i'm still getting the problem. Could the ignition amp be an issue here? I have had a look around the regular on line shops for dizzy caps and rotors which should I get? There are some offering the OE blue caps are these the correct item. Cheers all.

[jamienshelly]

It may be worth while removing the plug extenders and fire it up (not for long) as they can cause intermittent misfires, misfires under load or just running like a bag of crap. if its ok without then get a new set or the heatproof socks that have been mentioned. I would expect coil problems at higher revs as with the amp unit. Good luck and please post your findings for us all to remember to check in the future...
Jamie

[ButtonIt]

Exactly the same as mine. Removed the extenders and they run beautifully. Put them back on and it runs like a three legged dog.

[Tri2Tri]

It was me that posted the removal of the extenders and fitted heat resistant socks at the time of my refurb. It did run well for a while. Not so good now around town at lower revs and really sounds like its not firing on all cylinders but the temperature check at the exhaust headers show all running at the same temperature plus all leads are sparking. I have just changed out the coolant temp sensor but this has made no difference. Pointers for the best cap and rotor or linky to website would be good. Once I have those changed out and timming checked I will get back.

[ButtonIt]

I bought a whole ignition kit (coil, dizzy, rotor, leads from Racetech and those bits were fine (or seem to be at the moment). I got the extenders from somewhere else, can't remember where although it was supposedly a TVR specialist. I don't know what to do next.

[Tyre Tread]

Tri2Tri said:

It was me that posted the removal of the extenders and fitted heat resistant socks at the time of my refurb. It did run well for a while. Not so good now around town at lower revs and really sounds like its not firing on all cylinders ...

Do you think that there may be a correlation between no plug extenders and your misfire? Maybe the leads might be breaking down due to heat transfer despite the 'socks'?

[ButtonIt]

I've just dropped my Chim in with Topcats Racing near Aylesbury, hopefully they can sort my poor little motor out. I drove it there with no extenders, but the leads were only millimetres away from the manifold and it started running lumpy about a third of the way there.

[Tri2Tri]

Ok just an update.
New lucas dizzy cap and rotor arrive and replaced as a matter of course. Problem still there.
Next I checked to see if the vacuum advance was holding vacuum....Nope its not. Ordered a new vacuum advance waiting for delivery and we will see what happens when thats swapped out.
Timimg checked and that all seemed ok.
Bought a lead from Blitz for rovergauge....Interesting as i have not a clue what im looking at but the lambda sensors dont seem right running at -100%. Once I have changed out the vacuum advance I will check with rovergauge and post findings. No fault codes logged though.
I have been informed that the problem seems to be a lean burn misfire.....it is using a lot of fuel.

Edited by Tri2Tri on Thursday 22 May 15:45

[yknot]

See my thread here;

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Had a misfire/misfuel problem for ages without any fault codes being registered and tried all the things you are looking at dizzy/rotor/plugs/leads etc, etc. without any change. The problem with mine was an intermittent fault so was a right b....r to track down!!!

Eventually the ECU registered the fault codes (17 and 19) and the culprit revealed!!

Just a thought??

[blitzracing]

If both lambdas are running at 100% it could be a chronic misfire on both banks- a misfire reads as a lean mixture- so you would see 100% adding fuel trim, plus the plugs are likely to be sooty. If its affecting both banks- its really down to coil, coil supply, king lead, amp or trigger in the dizzy. Anything in the dizzy cap / rotor / plug leads is unlikely to affect both banks in the same way. A failed Vacuum advance wont make it misfire- just use more fuel. What plug leads are you running?

[Tri2Tri]

Plug leads were new a few hundred miles ago, they were standard Bosche. Once I fit the vacuum advance I will rig up the rovergauge and get a couple of screen shots posted before the weekend hopefully.