Mystery misfire V8s
Discussion
Wonder if any of you can help, today being such a nice day I got the V8s out of the garage and gave it a good run. No mishaps and it ran perfectly. Left it on the drive, 3 hrs later set of in it only for it to start to misfire just down the road, i also noticed a strong smell of petrol. I pulled over lifted bonnet could see nothing wrong closed bonnet a started it back up, all ran fine.
Got to my destination, left it standing for 5 mins, set off home and same problem just after set off. Stopped again lifted bonnet see nothing worng, close bonnet re start and alls fine.
Latest work carried out was a fuel pump change at begining of week, and a spark plug change using NGK 7 ECS plugs but it ran fine afterwards with no probs at all.
This is the first time it has done this. Any clues or pointers anybody.
Thanks
Pete
Got to my destination, left it standing for 5 mins, set off home and same problem just after set off. Stopped again lifted bonnet see nothing worng, close bonnet re start and alls fine.
Latest work carried out was a fuel pump change at begining of week, and a spark plug change using NGK 7 ECS plugs but it ran fine afterwards with no probs at all.
This is the first time it has done this. Any clues or pointers anybody.
Thanks
Pete
Thanks for the reply Tinks, the leads are magnacor, plug extenders are all recent, coil changed, the distributor is good as it was overhauled at the back end of last year and should be ok though i will check it. I was thinking ingnition module maybe but not sure why turning the car off then back on again will clear it.
sparkypete said:
Latest work carried out was a fuel pump change at begining of week, and a spark plug change using NGK 7 ECS plugs but it ran fine afterwards with no probs at all.
Its got to be one of these... I presume the plug gaps are all OK and they are in tight and leads connected OK, but my money is on the fuel pump...why did you replace yours in the first place? if everything else was working OK and you changed this and see this new (?) problem, its got to be related...
K
Ketvin thanks for the reply.
I replaced the pump as the old one just stopped working, one minute the car was warming up in the garage, the next it died. There after the pump would not prime or make any noise. Checked all electrical conections and decided that the pump was dead. I had a spare 2nd hand pump which i fit, I then took it for a long run with no worries at all until now. My question, would the pump make it missfire and stutter, and if so why would it be fine after just switching off then on ??
I will be removing the plugs tonight to check these.
Maybe i should sort a new pump
Any further advice greatfully accepted.
I replaced the pump as the old one just stopped working, one minute the car was warming up in the garage, the next it died. There after the pump would not prime or make any noise. Checked all electrical conections and decided that the pump was dead. I had a spare 2nd hand pump which i fit, I then took it for a long run with no worries at all until now. My question, would the pump make it missfire and stutter, and if so why would it be fine after just switching off then on ??
I will be removing the plugs tonight to check these.
Maybe i should sort a new pump
Any further advice greatfully accepted.
This doesn't sound quite like a problem I had, but worth checking-
The underside of the hose from the AFM to the plenum had perished away (not visible from the top. Only when I floored it, asking the engine to suck a load of air in, it sucked air in that the AFM didn't know about causing a very lean mixture and a heavy misfire/jolt under load.
New hose solved the problem.
Grant
The underside of the hose from the AFM to the plenum had perished away (not visible from the top. Only when I floored it, asking the engine to suck a load of air in, it sucked air in that the AFM didn't know about causing a very lean mixture and a heavy misfire/jolt under load.
New hose solved the problem.
Grant
I'm not to sure about the set up on the V8 but it sounds as though it could be the engine temperature sensor either the sensor or wireing which is telling the ECU the engine is cold and overfueling. Switching off and re-starting is clearing the error, I would give the connections a quick check and clean. Just a thought.
Tony
Tony
Edited by merky300 on Monday 12th May 09:33
Edited by merky300 on Monday 12th May 09:34
merky300 said:
I'm not to sure about the set up on the V8 but it sounds as though it could be the engine temperature sensor either the sensor or wireing which is telling the ECU the engine is cold and overfueling. Switching off and re-starting is clearing the error, I would give the connections a quick check and clean. Just a thought.
Tony
That's where I would start too, then an air leak.Tony
Right
checked fuel and engine temp sensors from the ECU, all results are as expected, same goes for the injectors again all check out back at the ECU so the wiring and connections are good, I will need to run it up to temp then check again to see of any of them are breaking down due to heat.
I have also checked the dis cap and rotor arm, leads and extenders which appear good, though only chenged them last Autumn.
Dizzy advance mech is working and the weights appear to be free.
As i said I have recently had to change the petrol pump last Tuesday for a spare 2nd hand one i had due to failure of the old one, not sure if this could have any bearing on the problem, so i have ordered a new Bosch one to be sure.
Any ideas greatfully received.
Pete
checked fuel and engine temp sensors from the ECU, all results are as expected, same goes for the injectors again all check out back at the ECU so the wiring and connections are good, I will need to run it up to temp then check again to see of any of them are breaking down due to heat.
I have also checked the dis cap and rotor arm, leads and extenders which appear good, though only chenged them last Autumn.
Dizzy advance mech is working and the weights appear to be free.
As i said I have recently had to change the petrol pump last Tuesday for a spare 2nd hand one i had due to failure of the old one, not sure if this could have any bearing on the problem, so i have ordered a new Bosch one to be sure.
Any ideas greatfully received.
Pete
Gents,
Had this on my V8S, - when I had her!
I swapped the ignition amp on the side of the dissy and this seemed to sort the problem.
The amp does get extremely hot, attached as it is to the dissy on the pre-serp engines.
My thoughts were - misfire - obvious pong of unburnt fuel - leave to cool - problem seemed to go. So, must be something on the ignition side....hence my gut feel for the ignition amp.
They are not v. expensive - about £26 - for an intermotor pattern part. But if you can get an original Lucas.
Nick
Had this on my V8S, - when I had her!
I swapped the ignition amp on the side of the dissy and this seemed to sort the problem.
The amp does get extremely hot, attached as it is to the dissy on the pre-serp engines.
My thoughts were - misfire - obvious pong of unburnt fuel - leave to cool - problem seemed to go. So, must be something on the ignition side....hence my gut feel for the ignition amp.
They are not v. expensive - about £26 - for an intermotor pattern part. But if you can get an original Lucas.
Nick
Cant beat this place for help and advice can you 
Chris the cam was changed approx 25000 miles ago for a fast road type, the mileage is approx 57000 at the mo.
I thought it could be the amp, however the fault dissapears as soon as the ignition is switched of and then back on, no need to allow it to cool, it then runs smooth even though the engine heat is still hot, may be worth getting the module checked out.
If it continues i will book it in somewhere, however there is a shortage of engine diagnostic garages round here who i could trust with it.
Many thanks
pete
Chris the cam was changed approx 25000 miles ago for a fast road type, the mileage is approx 57000 at the mo.
I thought it could be the amp, however the fault dissapears as soon as the ignition is switched of and then back on, no need to allow it to cool, it then runs smooth even though the engine heat is still hot, may be worth getting the module checked out.
If it continues i will book it in somewhere, however there is a shortage of engine diagnostic garages round here who i could trust with it.
Many thanks
pete
Well I have replaced the petrol pump for a new one as the problem only started when i replaced the original knacked pump for a 2nd hand one i had.
I have also altered the timing to approx 12 BTDC from 8 BTDC, this does seem to have made a marked difference to its running with no obvious pinking.
All seemed great on the test run so I will have to see how it behaves.
Many thanks for you suggestions, I will keep you informed and no doubt I will be back if the problem insists.
Pete
I have also altered the timing to approx 12 BTDC from 8 BTDC, this does seem to have made a marked difference to its running with no obvious pinking.
All seemed great on the test run so I will have to see how it behaves.
Many thanks for you suggestions, I will keep you informed and no doubt I will be back if the problem insists.
Pete
Gassing Station | S Series | Top of Page | What's New | My Stuff