Engine stutters at constant speed

[ButtonIt]

Weird problem with my 400.

My little car had been sitting for a while doing nothing (about 8 weeks). The battery is new, only 6 months old, but was flat. I jumped it from my daily drive and set away for the weekend. I did well over 300 miles over about 5 days before it developed this strange fault.

When holding the car at a steady cruise the engine would stutter and lose power. If I floor it everywhere at full tilt it's fine, seems only to be when trying to cruise, and this happens at any speed.

Not entirely sure what's going on, any ideas would be grateful. I've got this weekend to get it fixed proper as I need it desperately. My BMW got nicked on Monday and I don't have a courtesy car on my policy.

Many thanks,
Chris

[s p a c e m a n]

Spark. Leads, plugs, dizzy etc. Sounds exactly like what my one does when one of the leads has popped off, I drove all the way to silverstone with 2 loose ones last week

[marks3drtaz]

Disconnect the earth lead for 30 secs then reconnect all should be fine, mine does this if I jump start.

Mark

[JFReturns]

s p a c e m a n said:

Spark. Leads, plugs, dizzy etc. Sounds exactly like what my one does when one of the leads has popped off, I drove all the way to silverstone with 2 loose ones last week

This, and give the stepper motor a clean for good measure.

[ButtonIt]

The infamous Number 8!! Plug extender had twisted round and burnt the lead on the manifold. Looking for new lead and extenders now, but fixed it temporarily for the time being. tHanks chaps

[hot metal]

ButtonIt said:

The infamous Number 8!! Plug extender had twisted round and burnt the lead on the manifold. Looking for new lead and extenders now, but fixed it temporarily for the time being. tHanks chaps

Same happened to me the other day, although it was my fault, must have moved it when I was checking the manifold bolts. The blew straight off the dizzy.

[ButtonIt]

Well, it seems that wasn't the only culprit!!

120 mile journey to Portsmouth this morning. Did the first 60 miles (mixture of country roads, A roads and M25) with no problem. Got onto the A3 and all of a sudden, no power. Lasted about 5 seconds and then *bang* it picked up again. It did this several times. I pulled over and let the engine idle, it hunted and nearly conked out a couple times and then just died. Started again first time and was fine for another 10 mile, but then lost power again. No warning lights or anything, just started slowing down. I put the clutch down to try to rev it and nothing. Dropped a gear and tried to power the engine back into life, but just continued slowing down. Then all of a sudden it picked up again.

Weird.

I'm now thinking fuel pump? Something like that?

[hot metal]

I had a coil problem like this on my Griff, it would die but start again almost straight away, a few seconds. It would only do it now & then.

[ButtonIt]

OK, so new coil worth a try? It's not a bad shout since mine is ancient.... fit that at same time as new rotor arm, dizzy, leads and extenders.

[s p a c e m a n]

When you dropped the clutch did it die completely or keep stuttering along? If it was still firing in any way I would look towards fuel starvation, whenever I've had a coil die it has been all or nothing.

• Thats aslong as your rotor, dizzy etc are all ok.

Edited by s p a c e m a n on Tuesday 20th August 10:09

[ButtonIt]

It was dying, nothing going on at all and would've stopped completely had I not brought the clutch out again.

[s p a c e m a n]

Yeah, agree with above then. If it would cut completely then still spark, coil, king lead, dizzy, rotor.

[cureton]

Do you say the stuttering at cruise has gone, its now more like a loss in power? Check the cable connector on the speed sensor at the diff.

[ButtonIt]

Yeah, cruise stuttering has gone since I moved number 8 plug extender away from my exhaust pipe

What does the speed sensor have to do with the running of the engine? Just curious...

[ButtonIt]

BLOODY NUMBER 8!!

It's all coming back to this... plug extender was loose. Not proper loose, but just a bit loose and obviously not allowing the spark. I found out on the side of the M27 this morning. Not the easiest thing to do, them buggers are hot!!

Anyway, new set being delivered today. Just got to drive the 120 miles back to my house tomorrow to fit them Got a whole ignition kit from Racetech as well, coil, upgraded leads, dizzy cap and rotor. Plug extenders were cheaper from ACT.

Edited by ButtonIt on Wednesday 21st August 08:32