Intermittent loss of power - help, please!
Discussion
Just recently my '98 Serp 500 has been giving a bit of trouble, randomly the engine will just stop firing and lose power, sometimes just for a split second, sometimes for a few seconds before recovering.
It can happen at any time I'm moving and it's like someone just turned off the ignition for a second or so.
I suspect it is electrical, as when it happens it is followed by the smell of unburned petrol.
I also suspect a loose connection (earth?) as it seems to happen more over rough road, particularly when hitting a 'jolt' in the road. But could it be the distributer or the coil? I'm a total numpty and am guessing I'm afraid.
Anyone had any similar symptoms and know the fix? Where would I find the main earthing points to check their security?
Any advice welcome before it gets worse - it is my daily driver so stuck without it.
Thanks in advance.
It can happen at any time I'm moving and it's like someone just turned off the ignition for a second or so.
I suspect it is electrical, as when it happens it is followed by the smell of unburned petrol.
I also suspect a loose connection (earth?) as it seems to happen more over rough road, particularly when hitting a 'jolt' in the road. But could it be the distributer or the coil? I'm a total numpty and am guessing I'm afraid.
Anyone had any similar symptoms and know the fix? Where would I find the main earthing points to check their security?
Any advice welcome before it gets worse - it is my daily driver so stuck without it.
Thanks in advance.
Check the positive electric connection on the fuel pump. Its very exposed to road dirt and wet. Can get very loose and rusty. Easier to check than the earths.
Main chassis earth is under offside wheel arch. Bright clean with emery and bolt tight. A difficult earth at front end of offside chassis rail, got at through front radiator opening on the Griff.
Smell of petrol may indicate a misfire. Check ignition leads in particular the HT lead to the coil from the dizzy.
Main chassis earth is under offside wheel arch. Bright clean with emery and bolt tight. A difficult earth at front end of offside chassis rail, got at through front radiator opening on the Griff.
Smell of petrol may indicate a misfire. Check ignition leads in particular the HT lead to the coil from the dizzy.
Edited by EGB on Tuesday 7th August 22:29
I had the same problem some years ago. Rather scarily it happened twice while trying to over take. 
At the time it was though likely to be a faulty Air Flow Meter. The car went into storage for unrelated reasons with the intention of getting the AFM replaced when it was back on the road.
When the time came I replaced the coil, dizzy cap, and HT leads as a matter of course. One of the HT leads had a chunk cut out of the insulation down to the wire. I suspect that was the problem, but there was also a hair line crack in the dizzy cap, and the I don't think the coil was in great condition. One or all of these issues could have caused the original problem, but after a year of the car being back on the road I've not (fingers crossed) had a repeat of the same loss of power that you described.
At the time it was though likely to be a faulty Air Flow Meter. The car went into storage for unrelated reasons with the intention of getting the AFM replaced when it was back on the road. When the time came I replaced the coil, dizzy cap, and HT leads as a matter of course. One of the HT leads had a chunk cut out of the insulation down to the wire. I suspect that was the problem, but there was also a hair line crack in the dizzy cap, and the I don't think the coil was in great condition. One or all of these issues could have caused the original problem, but after a year of the car being back on the road I've not (fingers crossed) had a repeat of the same loss of power that you described.
Edited by GJR on Tuesday 7th August 22:51
Ian,
I've still got something similar, which appears to be a bank shutting down, ie no power and chucking neat fuel out the back. If I switch off it is OK again but randomly happens which is very worrying as its alweays on your mind.
This was one of many issues I had. The others were iffy wires and it kept cutting out and eventually died which were cables hanging on near the coil area, which have been replaced so no cutting out just this random loss of a bank.
The bank loss is beleived to be where all the earths are spliced into one so follow the injectors back to find this and maybe the comnnections are furred up or worse. If you have some pics thant would also help me as I need to do this. I've got a node tester (thanks to Mark (blitzracing)) which I haven't used but since I've had it the runing has been fine - typical. If you want to borrow it I'm sure Mark would be OK with this. As you know we're in redditch so not a million miles away.
FFG
I've still got something similar, which appears to be a bank shutting down, ie no power and chucking neat fuel out the back. If I switch off it is OK again but randomly happens which is very worrying as its alweays on your mind.
This was one of many issues I had. The others were iffy wires and it kept cutting out and eventually died which were cables hanging on near the coil area, which have been replaced so no cutting out just this random loss of a bank.
The bank loss is beleived to be where all the earths are spliced into one so follow the injectors back to find this and maybe the comnnections are furred up or worse. If you have some pics thant would also help me as I need to do this. I've got a node tester (thanks to Mark (blitzracing)) which I haven't used but since I've had it the runing has been fine - typical. If you want to borrow it I'm sure Mark would be OK with this. As you know we're in redditch so not a million miles away.
FFG
At tickover stationary. Bonnet up. Try tickling the ignition leads including the dizzy to coil lead (king lead) with an insulated screw driver to try to reproduce the problem. Problem is typical of a missing poor connection king lead.
Rev enginer in a dark garage to check leads for arcing. Leave the door open for ventilation.
Rev enginer in a dark garage to check leads for arcing. Leave the door open for ventilation.
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back - It all began with a 'face off' with an XJR and when i booted the 'loud' pedal the car suddenly 'died' on me with the rev counter hitting zero and within a split second off the gas pedal the car suddenly sprang back into life. Normal driving, gave no problems at all, it was only when 'hard booting' the loud pedal. I took the car to Neil Garner Performance Engineering for Neil to personally test himself. The problem happened with Neil 'on hard test.' At first Neil himself was unsure what exactly was causing the problem and hadn't experienced this before. So going back to basics with certain tests, Neil diagnosed the problem within minutes - with what I believe to be was the ignition relay at the front of the engine had rusted. Fortuately a spare was in stock and the problem hasn't come back since. As said, I am not mechanically minded, but it does sound similar to my problem and if you need further advice, I advise you to give Neil a call - 01666 577449 (He knows my Griff well) Good luck and hope you get the problem sorted.
However, I experienced something similar to this, a couple of month's back - It all began with a 'face off' with an XJR and when i booted the 'loud' pedal the car suddenly 'died' on me with the rev counter hitting zero and within a split second off the gas pedal the car suddenly sprang back into life. Normal driving, gave no problems at all, it was only when 'hard booting' the loud pedal. I took the car to Neil Garner Performance Engineering for Neil to personally test himself. The problem happened with Neil 'on hard test.' At first Neil himself was unsure what exactly was causing the problem and hadn't experienced this before. So going back to basics with certain tests, Neil diagnosed the problem within minutes - with what I believe to be was the ignition relay at the front of the engine had rusted. Fortuately a spare was in stock and the problem hasn't come back since. As said, I am not mechanically minded, but it does sound similar to my problem and if you need further advice, I advise you to give Neil a call - 01666 577449 (He knows my Griff well) Good luck and hope you get the problem sorted.
[quote=marz92]Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
EGB said:
marz92 said:
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Having just looked up 'DAB 118' thanks to Google - You could well be right - Just not the expert when it comes to lifting up the bonnet! As said, perhaps for the owner with the query, if he speaks to Neil - He's the expert and no doubt help with the problem! Certainly not me!However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Edited by marz92 on Wednesday 8th August 23:11
EGB said:
marz92 said:
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Having just looked up 'DAB 118' thanks to Google - You could well be right - Just not the expert when it comes to lifting up the bonnet! As said, perhaps for the owner with the query, if he speaks to Neil - He's the expert and no doubt help with the problem! Certainly not me!However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Edited by marz92 on Wednesday 8th August 23:11
EGB said:
marz92 said:
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Having just looked up 'DAB 118' thanks to Google - You could well be right - Just not the expert when it comes to lifting up the bonnet! As said, perhaps for the owner with the query, if he speaks to Neil - He's the expert and no doubt help with the problem! Certainly not me!However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Edited by marz92 on Wednesday 8th August 23:11
EGB said:
marz92 said:
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Having just looked up 'DAB 118' thanks to Google - You could well be right - Just not the expert when it comes to lifting up the bonnet! As said, perhaps for the owner with the query, if he speaks to Neil - He's the expert and no doubt help with the problem! Certainly not me!However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Edited by marz92 on Wednesday 8th August 23:15
EGB said:
marz92 said:
Thought I would add my two penny worth - not that I am any good with mechanics....
However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Having just looked up 'DAB 118' thanks to Google - You could well be right - Just not the expert when it comes to lifting up the bonnet! As said, perhaps for the owner with the query, if he speaks to Neil - He's the expert and no doubt help with the problem! Certainly not me!However, I experienced something similar to this, a couple of month's back -
What was this rusty ignition relay ?? Did you mean the ignition module between the dizzy and the distributer? Thanks.
Edited by marz92 on Wednesday 8th August 23:15
Could be the back emf from the coil and RPM in-line dropping resistor problem, especially as it tends to occur when ramping up the revs. See here:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
It's the same LT circuit as the ignition amp, so I'd check both.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
It's the same LT circuit as the ignition amp, so I'd check both.
Fixed it!! Aren't I lucky!! I found the problem was a dodgy wire connection in the wiring loom near the ECU. All I had to do was re-crimp the connection and bingo, no more intermittent power loss.
Had already cleaned up the earths in the engine bay, but it made no difference. Was beginning to suspect an ignition amp but why would it fail intermittently? So I started the engine, and jiggled the ECU box and the engine died. That's when I spotted the dodgy wire.
Simple - thank goodness. I wish all issues were as simple to fix.
Over the weekend I drove about 500 miles all with the roof off; Herefordshire, to Coventry to Kent to Coventry to Herefordshire and it didn't miss beat, even when stuck in the jam approaching the Dartford tunnel. It sounded great going through that!!
The only issue I had was a hot start problem at a service station in Coventry on the way home. But it only took 5 minutes until it fired again.
Happy days.
Had already cleaned up the earths in the engine bay, but it made no difference. Was beginning to suspect an ignition amp but why would it fail intermittently? So I started the engine, and jiggled the ECU box and the engine died. That's when I spotted the dodgy wire.
Simple - thank goodness. I wish all issues were as simple to fix.
Over the weekend I drove about 500 miles all with the roof off; Herefordshire, to Coventry to Kent to Coventry to Herefordshire and it didn't miss beat, even when stuck in the jam approaching the Dartford tunnel. It sounded great going through that!!
The only issue I had was a hot start problem at a service station in Coventry on the way home. But it only took 5 minutes until it fired again.
Happy days.
FlipFlopGriff said:
Glad it was easy. Sounds like you had a lucky break.
FFG
Just my 2 Penrneth Paul. Is it the same bank falling off when it happens. My peneth suggestion is., something I would try. Sationary have the.engine at say 2000rpm. (brick on the pedal?) Jiggle all the electric cables by hand like the Red Baron, to see if the one bank drop off can be reproduced. Good luck mate. Goodwood now sorted. The choice better be b.......dy good!FFG
Edited by EGB on Tuesday 21st August 20:07
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