Mis fire and near stalling
Discussion
Hi all....after mearly a whole week of fine running the chim is back on axle stands!!!
The car starts up ok...but then struggles to keep going below 1.5k revs...it back fires, splutters and feels as though it is running out of petrol...it has got a full tank!!!
If i slip the clutch and build the revs up it flys along when it gets to above 2.5k revs.
I was thinking possibly blocked fuel filter but surely this will cause a shortage of fuel at higher revs rather than it flying along...???
Had a look at removing the fuel filter and it looks a pig of a job.
The car starts up ok...but then struggles to keep going below 1.5k revs...it back fires, splutters and feels as though it is running out of petrol...it has got a full tank!!!
If i slip the clutch and build the revs up it flys along when it gets to above 2.5k revs.
I was thinking possibly blocked fuel filter but surely this will cause a shortage of fuel at higher revs rather than it flying along...???
Had a look at removing the fuel filter and it looks a pig of a job.
Was it behaving like this when you had the overfuelling problems, or did it start doing this when you fixed the fuelling probs (new ECU with the old chip iirc?), or did this new problem crop up some time afterwards? Has anything else been changed around the time it started?
What state are the plugs in?
Do you have a timing light? What is the spark doing?
Daves suggestion of an an air leak would fit most of the symptoms, in which case I'd expect the problem to go away when you open the throttle. Check for hoses come adrift and see whether the revs pick up when you spray carb cleaner round the outside of the plenum and intake system downstream of the AFM. Don't spray it anywhere it could get drawn into the intake upstream of the AFM.
Given that you have had lots of fuelling related problems recently and this feels kind of similar, gut feeling is this is the same problem on a smaller scale. Do you have any way to measure the actual fuel pressure? You could try pulling the vac line to the fuel pressure regulator off the plenum, this will richen it up loads, if the fuel supply was right before it will cough and splutter and start dropping cylinders with masses of fuel coming out the back. If it seems to make an improvement I'd take that as a sign that it was running very lean before.
What state are the plugs in?
Do you have a timing light? What is the spark doing?
Daves suggestion of an an air leak would fit most of the symptoms, in which case I'd expect the problem to go away when you open the throttle. Check for hoses come adrift and see whether the revs pick up when you spray carb cleaner round the outside of the plenum and intake system downstream of the AFM. Don't spray it anywhere it could get drawn into the intake upstream of the AFM.
Given that you have had lots of fuelling related problems recently and this feels kind of similar, gut feeling is this is the same problem on a smaller scale. Do you have any way to measure the actual fuel pressure? You could try pulling the vac line to the fuel pressure regulator off the plenum, this will richen it up loads, if the fuel supply was right before it will cough and splutter and start dropping cylinders with masses of fuel coming out the back. If it seems to make an improvement I'd take that as a sign that it was running very lean before.
andy-w said:
Just taken the fuel filter off and the arrow for fuel flow was pointing away from the fuel pump heading towards the front of the car - is this right? I would have thought it would've pointed to the fuel pump? Assuming that the filter is between the tank and the pump.
I would expect to find the filter is downstream from the pump so the arrow is correct as it is. You can follow the fuel line from the filter back to the pump to verify this.
i just assumed that the filter would have been between the tank and the pump.
The problem came about over a couple of days...it misfired a few times on my way to work one morning and was fine on the way home...the next day it misfired a few more times and then on my way home it was misfiring quite bad...now it is very rough at low revs but fine when accelerating hard over 2k revs and when ticking over in neutral it is hunting at idle and backfiring.
Nothing has been changed since i changed the ecu...all hoses look well fastened and in the right place.
The visible thing i can see in the engine bay is a slight leak from the rocker covers but it is slight and has been there since before changing the ecu.
Before the misfiring problem the car was running excellent.
The plugs were a slightly black colour but were nowhere near as coked up as they were when it was running rich.
The problem came about over a couple of days...it misfired a few times on my way to work one morning and was fine on the way home...the next day it misfired a few more times and then on my way home it was misfiring quite bad...now it is very rough at low revs but fine when accelerating hard over 2k revs and when ticking over in neutral it is hunting at idle and backfiring.
Nothing has been changed since i changed the ecu...all hoses look well fastened and in the right place.
The visible thing i can see in the engine bay is a slight leak from the rocker covers but it is slight and has been there since before changing the ecu.
Before the misfiring problem the car was running excellent.
The plugs were a slightly black colour but were nowhere near as coked up as they were when it was running rich.
Peculiar. The way it has come up gradually makes me suspect that the problem may be caused by dirty plugs. I suggst you fit new plugs and see if that makes any difference. That isn't the whole problem because the plugs should last many thousands of miles if the rest of the engine is OK, but would at least confirm what the immediate problem is.
Are you running NGK B7ECS? These are the recomended plug but are a fairly cold grade and not brilliant at self cleaning, so they're a bit vulnerable if the engine is out of tune.
Are you running NGK B7ECS? These are the recomended plug but are a fairly cold grade and not brilliant at self cleaning, so they're a bit vulnerable if the engine is out of tune.
GreenV8S said:
Are you running NGK B7ECS? These are the recomended plug but are a fairly cold grade and not brilliant at self cleaning, so they're a bit vulnerable if the engine is out of tune.
I have got B7ECS plugs in....they were not brand new (About 1000 miles old but i gave them a good clean) and it was doing it with the other plugs in as well.
Might be worth having a go with the ecu fault code reader...maybe with the new ecu in it might come up with something.
Have ordered a new fuel filter as the one on there looked very old and for the sake of £6 it seemed rude not too!!!!
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