Running like a pig
Discussion
I wonder if someone can help me diagnose a problem.
Ths car starts up fine and runs well at first. After running for a while I occasionally find that there is a "limit" to the revs ~ it's like I've hit a ceiling. If I push the clutch in I can rev as high as I like but as soon as I let the clutch out it splutters again. I find that if I stop the engine and start up again the problem goes. The engine only has to be turned off momentarily.
When the problem first arose I thought it was dirty fuel. The car had just had a repair to the fuel tank and there was a fair bit of loose rust in it. I cleaned the fuel line to the pump many times and eventually fitted an inline filter ~ however it didn't sort it.
I have also changed the throttle pot.
One thing that did make a big difference was to start her up from cold and leave idling 'till the fan cut in. This tip was from TVRGit who says it resets various electrical gizmos.
The problem has been with me for a while.
August is a bit hectic here so the car hadn't been driven for about a month. The battery was flat so I disconnected it and recharged. Before driving again I deployed TVRgit's tip.
So on my first outing yesterday she started well. Engine was nearly up to normal temp when I hit the main road, revs up to 5500 and she roared like a dream. 5 miles later she was spluttering like a pig ~ worse than it had been for ages.
So, what can I check and how do I do it?
This problem is begining to get me down so any help would be appreciated.
Cheers
Tim
Ths car starts up fine and runs well at first. After running for a while I occasionally find that there is a "limit" to the revs ~ it's like I've hit a ceiling. If I push the clutch in I can rev as high as I like but as soon as I let the clutch out it splutters again. I find that if I stop the engine and start up again the problem goes. The engine only has to be turned off momentarily.
When the problem first arose I thought it was dirty fuel. The car had just had a repair to the fuel tank and there was a fair bit of loose rust in it. I cleaned the fuel line to the pump many times and eventually fitted an inline filter ~ however it didn't sort it.
I have also changed the throttle pot.
One thing that did make a big difference was to start her up from cold and leave idling 'till the fan cut in. This tip was from TVRGit who says it resets various electrical gizmos.
The problem has been with me for a while.
August is a bit hectic here so the car hadn't been driven for about a month. The battery was flat so I disconnected it and recharged. Before driving again I deployed TVRgit's tip.
So on my first outing yesterday she started well. Engine was nearly up to normal temp when I hit the main road, revs up to 5500 and she roared like a dream. 5 miles later she was spluttering like a pig ~ worse than it had been for ages.
So, what can I check and how do I do it?
This problem is begining to get me down so any help would be appreciated.
Cheers
Tim
It sounds to me as though a fuel filter is getting progressively blocked and when you close off the dirt is being allowed to float away from the filter thus allwing fuel through untill such time as it is pulled back onto the filter and the process starts again. You say you have fitted an In-Line filter but I beleive the system has its own filter, have you checked that.It seems a bit of a coincidence that this started after the fuel tank issue.
Hi Tim - When you started from idle to warm up, did you disconnect the battery for a while first? I believe when the battery is disconnected the ecu losses its memory, therefore it will reteach itself during the warm up to fan coming on, then turn off and restart.
It does sound like feul starvation to me, did you remove the internal tank filter after having the work done on the tank, as rubbish could be collecting around the filter, then when you turn the engine off it falls away until being drawn back again, I removed mine and like you fitted an inline filter. Is the filter letting enough feul through - mine is used on a 3.0 Vauxhall Senitor. As you may get enough pressure to have a blast before feul shortage,althrough the pressure should build up when you reduce speed.
Is any air getting in to weaken the mixture - this may explain being able to rev on clutch but not during driving, however it seems to be strange that this all started after the work on the tank was done.
Ive just got mine going again after fitting a new pump (£56)- not that this is a issue to your problem, but the pump seemed alot larger than the old one, so I think that it may output a larger amount of pressure - seen as it blew one of the pipes off which I hadnt disconnected.
I know how frustrating it can be when you have problems that are difficult to find. Best of luck.
Sean
It does sound like feul starvation to me, did you remove the internal tank filter after having the work done on the tank, as rubbish could be collecting around the filter, then when you turn the engine off it falls away until being drawn back again, I removed mine and like you fitted an inline filter. Is the filter letting enough feul through - mine is used on a 3.0 Vauxhall Senitor. As you may get enough pressure to have a blast before feul shortage,althrough the pressure should build up when you reduce speed.
Is any air getting in to weaken the mixture - this may explain being able to rev on clutch but not during driving, however it seems to be strange that this all started after the work on the tank was done.
Ive just got mine going again after fitting a new pump (£56)- not that this is a issue to your problem, but the pump seemed alot larger than the old one, so I think that it may output a larger amount of pressure - seen as it blew one of the pipes off which I hadnt disconnected.
I know how frustrating it can be when you have problems that are difficult to find. Best of luck.
Sean
just come off phone to Tim and have discussed exactly the same suggestions as yourselves - since his fuel tank repair he removed the internal strainer for
inspection and found it dirty AND holed. Strainer was replaced and disconnected pipe from fuel pump and found the small filter in there clogged, removed cleaned and refitted and also fitted an inline filter between tank and pump to help prevent further problems(Yes in the reinforced pipe). Still same problem, has had fuel pressure tested at fuel rail whilst driven with a pressure guage gaffer taped to windscreen - garage says ok. It sounds very much like fuel but only happens when driven for a while and under load - classic starvation symptoms.
Problem is, without removing fuel rail and regulator how far can you go to prove fault when its only intermittent and when driving?
inspection and found it dirty AND holed. Strainer was replaced and disconnected pipe from fuel pump and found the small filter in there clogged, removed cleaned and refitted and also fitted an inline filter between tank and pump to help prevent further problems(Yes in the reinforced pipe). Still same problem, has had fuel pressure tested at fuel rail whilst driven with a pressure guage gaffer taped to windscreen - garage says ok. It sounds very much like fuel but only happens when driven for a while and under load - classic starvation symptoms.
Problem is, without removing fuel rail and regulator how far can you go to prove fault when its only intermittent and when driving?
Edited by pringli on Sunday 31st August 11:49
So if its not fuel, which the symptons suggest, but if there is pressure at the fuel rail could it be after the rail. Blocked injectors?
The big clue is - what is the change point between turning the engine on and off again, which appears to correct the issue only for a short time? It doesnt sound electrical to me, unless spark plugs start to fail when hot - unlikely, what colour are the plugs? it would tell you if it was running lean or rich. Sorry its not much help.
Sean
The big clue is - what is the change point between turning the engine on and off again, which appears to correct the issue only for a short time? It doesnt sound electrical to me, unless spark plugs start to fail when hot - unlikely, what colour are the plugs? it would tell you if it was running lean or rich. Sorry its not much help.
Sean
I drained mine, there is no drain plug - method
Wait until the missus has gone out.
Siphon out what you can - mmmm nice taste.
Jack car up - and remove rear wheel.
Get a big container.
Pull off the reinforced pipe and quickly put it into the container.
If there is a massive smell of petrol - tell the missus that one of the kids or dogs knocked over a can.
PS dont smoke - if it all goes wrong it wasnt my idea.
Sean
Wait until the missus has gone out.
Siphon out what you can - mmmm nice taste.
Jack car up - and remove rear wheel.
Get a big container.
Pull off the reinforced pipe and quickly put it into the container.
If there is a massive smell of petrol - tell the missus that one of the kids or dogs knocked over a can.
PS dont smoke - if it all goes wrong it wasnt my idea.
Sean
Edited by trickjohn on Sunday 31st August 12:29
He is lucky Sean, he has a pit - downside of that of course is that he can end up ankle deep in it.
ps we all seem to agree on restriction in fuel supply, problem is where is it and has it got past pump, hopefully not as the small filter in the pump inlet itself was intact although clogged with debris then cleaned and refitted so hopefully its at the tank end and not regulator/fuel rail.
ps we all seem to agree on restriction in fuel supply, problem is where is it and has it got past pump, hopefully not as the small filter in the pump inlet itself was intact although clogged with debris then cleaned and refitted so hopefully its at the tank end and not regulator/fuel rail.
Edited by pringli on Sunday 31st August 12:34
I unblocked mine by reversing the terminals on the pump, so you blow all the sh*te back into the tank and then drain it or put the fuel pipes from the injector end in a container of petrol and disconnect the pipe from the tank and reverse polarity a few times, changing the containers around so you dont draw back contaminated fuel.
I hope that makes sense, Sean
I hope that makes sense, Sean
It seems to me that theories about obstructions in the fuel supply have been completely ruled out by the tests with the fuel pressure gauge taped to the windscreen.
A weak spark would cause problems on load getting worse with revs, and the electrical faults which cause this can easily come and go as things are disturbed by heat and vibration.
I think the next sensible step is to see whether the problem is affecting the injection or ignition systems. A cheap passive strobe light as used for ignition timing is a good way to see whether you have a spark. Position the strobe so that you can see it from the driver's seat while driving, make sure the leads don't get near the exhaust.
You can buy NOID diagnostic lights which are inserted between the loom and an injector to see whether the injector is being triggered. These are fine when you have the bonnet up but no help when you're driving. What you need here is a pair of male and female connectors and a 12V LED, use these to wire the LED in parallel with the injector on a lead that is long enough to reach the back of the bonnet so you can see it. The standard connectors are called power mini timer connectors, they're cheap and easy to buy.
These tests will show whether the fuel supply is changing significantly when the problem occurs, also whether the spark is changing.
Since the fuel injection is triggered from the spark you may find they both fail, so if the ignition seems to be playing up fix that before you start chasing down fuel related problems.
A weak spark would cause problems on load getting worse with revs, and the electrical faults which cause this can easily come and go as things are disturbed by heat and vibration.
I think the next sensible step is to see whether the problem is affecting the injection or ignition systems. A cheap passive strobe light as used for ignition timing is a good way to see whether you have a spark. Position the strobe so that you can see it from the driver's seat while driving, make sure the leads don't get near the exhaust.
You can buy NOID diagnostic lights which are inserted between the loom and an injector to see whether the injector is being triggered. These are fine when you have the bonnet up but no help when you're driving. What you need here is a pair of male and female connectors and a 12V LED, use these to wire the LED in parallel with the injector on a lead that is long enough to reach the back of the bonnet so you can see it. The standard connectors are called power mini timer connectors, they're cheap and easy to buy.
These tests will show whether the fuel supply is changing significantly when the problem occurs, also whether the spark is changing.
Since the fuel injection is triggered from the spark you may find they both fail, so if the ignition seems to be playing up fix that before you start chasing down fuel related problems.
Edited by GreenV8S on Sunday 31st August 12:49
pringli said:
He is lucky Sean, he has a pit - downside of that of course is that he can end up ankle deep in it.
ps we all seem to agree on restriction in fuel supply, problem is where is it and has it got past pump, hopefully not as the small filter in the pump inlet itself was intact although clogged with debris then cleaned and refitted so hopefully its at the tank end and not regulator/fuel rail.
Bbe careful, Petrol is heavier than air so the pit could fill with fumes.ps we all seem to agree on restriction in fuel supply, problem is where is it and has it got past pump, hopefully not as the small filter in the pump inlet itself was intact although clogged with debris then cleaned and refitted so hopefully its at the tank end and not regulator/fuel rail.
Edited by pringli on Sunday 31st August 12:34
Ken, just being pedantic but assume you mean petrol fumes and is that a nervous stutter 
Peter, I agree about danger of being led down the wrong road and we discussed ignition problems when under load but, problem only started after fuel tank removal after problem spotted whilst garage was doing outriggers and car ran ok (so didnt actually prove anything)when being pressure tested - as they all do of course
Peter, I agree about danger of being led down the wrong road and we discussed ignition problems when under load but, problem only started after fuel tank removal after problem spotted whilst garage was doing outriggers and car ran ok (so didnt actually prove anything)when being pressure tested - as they all do of course
Edited by pringli on Sunday 31st August 13:17
I've been outside for a while ~ not near the computer. I've just come in to find that you have all been busy! Many thanks for your help.
If I give you a blow by blow account of events it may be of use.
The car had a leaking fuel tank and rotten outriggers ~ This was too much of a job for me so I took it to the local garage.
They did a partial body lift to repair the outriggers ( using information which I provided them that I gleaned from this site)
They sent the tank to a specialist who patched the hole and coated the outside of the tank.
When I got the car back I started to get the problems as previously described.
I took the car back to the garage and asked them to investigate.
They drained the tank, removed the fuel pump, fitted new fuel filter, fitted new plug leads and measured fuel pressure.
They said that the pressure was ok.
This was just over a year ago.
The problem has persisted to varying degrees.
In the I drained the tank and fitted a new strainer ( the old one had a hole in it). In fact I drained the tank several times by taking the bung out of the bottom. I also sloshed a gallon or so of fuel through the tank with the bung out to remove as much s
te as I could. ( There were a lot of small rust particles)
Where the hose connects to the pump there is a very small thimble like filter ~ this I have carefully taken out and cleaned.
I still had problems.
I then bought an inline bullet filter which I fitted between the tank and the pump thinking it would be the end of my woes ~ it wasn't.
I've tried the trick of starting from cold and idling til the fan goes off. It seems to improve things but may be my imagination.
Earlier on this year I only got the problem after running for an hour or so. If I immediately turned the engine off and started straight away it would go away for a while. If I tried to carry on without doing this it seemed to get worse.
I bought a new throttle pot ~ to no avail
Originally I was convinced that it was a fuel problem as that, I thought, was the only thing that had been changed. But, as time goes by I'm getting more confused.
Did the body lift stretch/kink/strain a wire/hose/connector?
Is there still some muck in the fuel system on teh engine side of the
filter?
Unfortunatly I'm not much of a mechanic and I don't understand how teh system works, let alone work out where it has gone wrong.
Thanks for your help ~ especially Pringli who spent the best part of an hour on the phone today telling me which leads/hoses etc were which.
Cheers
Tim
If I give you a blow by blow account of events it may be of use.
The car had a leaking fuel tank and rotten outriggers ~ This was too much of a job for me so I took it to the local garage.
They did a partial body lift to repair the outriggers ( using information which I provided them that I gleaned from this site)
They sent the tank to a specialist who patched the hole and coated the outside of the tank.
When I got the car back I started to get the problems as previously described.
I took the car back to the garage and asked them to investigate.
They drained the tank, removed the fuel pump, fitted new fuel filter, fitted new plug leads and measured fuel pressure.
They said that the pressure was ok.
This was just over a year ago.
The problem has persisted to varying degrees.
In the I drained the tank and fitted a new strainer ( the old one had a hole in it). In fact I drained the tank several times by taking the bung out of the bottom. I also sloshed a gallon or so of fuel through the tank with the bung out to remove as much s
te as I could. ( There were a lot of small rust particles)Where the hose connects to the pump there is a very small thimble like filter ~ this I have carefully taken out and cleaned.
I still had problems.
I then bought an inline bullet filter which I fitted between the tank and the pump thinking it would be the end of my woes ~ it wasn't.
I've tried the trick of starting from cold and idling til the fan goes off. It seems to improve things but may be my imagination.
Earlier on this year I only got the problem after running for an hour or so. If I immediately turned the engine off and started straight away it would go away for a while. If I tried to carry on without doing this it seemed to get worse.
I bought a new throttle pot ~ to no avail
Originally I was convinced that it was a fuel problem as that, I thought, was the only thing that had been changed. But, as time goes by I'm getting more confused.
Did the body lift stretch/kink/strain a wire/hose/connector?
Is there still some muck in the fuel system on teh engine side of the
filter?
Unfortunatly I'm not much of a mechanic and I don't understand how teh system works, let alone work out where it has gone wrong.
Thanks for your help ~ especially Pringli who spent the best part of an hour on the phone today telling me which leads/hoses etc were which.
Cheers
Tim
If the problem is caused by an obstruction in the fuel supply I don't see why it would make any difference what temperature you got the engine to and I find it hard to believe that stopping and restarting would do any good.
I think you're looking at an intermittent failure within the fuel or ignition systems. They can very easily cause symptoms like this and are very often intermittent.
I think you're looking at an intermittent failure within the fuel or ignition systems. They can very easily cause symptoms like this and are very often intermittent.
Without a lot of expense though how is he going to trace and clear. When I had the same problem with my scirocco the problem was an obstructed strainer in the fuel tank and that only presented itself when foot to floor or on long uphill stretches ie heavy load. Would have cost me a fortune via the VW dealership but when I called to book it in the girl on reception asked if I had checked that first as it was not uncommon.
ps when you switch off there is no pressure though the tank outlet so the debris falls away
ps when you switch off there is no pressure though the tank outlet so the debris falls away
Edited by pringli on Sunday 31st August 13:53
Had a similar problem many years ago - it was a spark plug failing and in so doing provided a false reading to the ecu which promptly shut down. Changed plugs - problem solved! [It was a Volvo however]
Another thought - typical symptom of restricted fuel line - damaged/kinked possibly, reducing fuel supply. Pressure readings wouldn't be affected at tick over.
Good luck.
Another thought - typical symptom of restricted fuel line - damaged/kinked possibly, reducing fuel supply. Pressure readings wouldn't be affected at tick over.
Good luck.
Bloody Hell Tim you sound like you are in the wars mate...
I agree with Peter that you have done all of the necessary jobs to the fuel system and should look elsewhere...
I know you replaced the TP, and must have checked that vacumn hose that I suggested, so you need to start looking again at your ignition system, so...
new leads = OK
new plugs ?
substitute Dissy -> I have two you can play with, Ian has one which I think he has tested and is good, the other was bought at SCH and is untested but you can try that one. both have ignition modules attached so that would rule that one out too.
what coil do you have? is it new? - again I have a spare coil which you can borrow to rule that one out...
I have a gunsens strobe which you can borrow
You could also borrow my spare AFM's if you havent already ruled those out...
finally a gunsens tester connected to the diagnostic plug just after you suffer the problem next time should give you a code that will point you to the part of the system that failed - hopefully...
I havent actually used it to do such a test and was hoping Graham would figure out how it worked and give me a blaggers guide... 
just let me know and I'll pop over later with any bits you want.
K
I agree with Peter that you have done all of the necessary jobs to the fuel system and should look elsewhere...
I know you replaced the TP, and must have checked that vacumn hose that I suggested, so you need to start looking again at your ignition system, so...
new leads = OK
new plugs ?
substitute Dissy -> I have two you can play with, Ian has one which I think he has tested and is good, the other was bought at SCH and is untested but you can try that one. both have ignition modules attached so that would rule that one out too.
what coil do you have? is it new? - again I have a spare coil which you can borrow to rule that one out...
I have a gunsens strobe which you can borrow
You could also borrow my spare AFM's if you havent already ruled those out...
finally a gunsens tester connected to the diagnostic plug just after you suffer the problem next time should give you a code that will point you to the part of the system that failed - hopefully...
I havent actually used it to do such a test and was hoping Graham would figure out how it worked and give me a blaggers guide... just let me know and I'll pop over later with any bits you want.
K
Thanks all for your help and advice.
I do think now that the problem is probably electrical rather than fuel.Especially seeing as the problem has got much worse since disconnecting the battery last week.
Kev ~ I'll take any help I can get! Many thanks for your offer. You have a much greater understanding of these things than I have. I'll contact you off board with a view to meeting up soon.
I'll report back here with our findings.
Cheers
Tim
I do think now that the problem is probably electrical rather than fuel.Especially seeing as the problem has got much worse since disconnecting the battery last week.
Kev ~ I'll take any help I can get! Many thanks for your offer. You have a much greater understanding of these things than I have. I'll contact you off board with a view to meeting up soon.
I'll report back here with our findings.
Cheers
Tim
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