Serious over fueling on '95 4.6

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ROBV8

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Hi chaps with the weather we are getting I thought I'd dig out my p38 which has been off road for about 2 years! I went to start it and it wouldn't go so took plugs out and they were soaked in fuel! Dried them out and blew cylinders out with airline. I warmed the plugs up with blow lamp and stuck them back in. She fired and ran! But did smoke like mad and stank of fuel. I switch it to gas and it ran lovely and smoking stopped quickly. I removed the tank as the gauge wasn't working so changed fuel while at it. Fired it up and ran ok and smoking stopped! Result I thought. Anyway left it running while I mucked about with other jobs and the running got lumpy and it smelt of fuel again so back on gas and all was good. I left it sat night and went to start it Sunday and nothing! Flooded big time. I've put a new coolant temp sensor in it and I did find the vacumme pipe to fuel pressure Reg was kinked so sorted that and it still does it! Only this time it runs bad on petrol from the off and won't idle and seems to miss fire? It's worse since the sensor and pipe? Runs lovely on gas tho. Sorry for going on but thought I'd get what I had tried in to start with. Any help appreciated as I need it on the road!
 
Seems strange that it runs fine on gas but so badly on petrol. Did you say you had put new petrol in it? Fuel filter OK, not clogged up (or missing!)?
 
if this happened after replacing the coolant sensor,it could b a possibility that sensor is telling the ecm tht car is cold thus pouring extra fuel to act as a choke,if this is the case i suggest u reset the adaptive values after checking 4 faults.
 
a clogged filter won't overfuel it ,it will starve from fuel !!! Over fueling is a cause of a bad sensor or leaking injectors.a duff maf will make the idle bad as well as overfueling and sometimes get the gearbox fault message as well as a high rpm and strange gear shifting.check 4 faults and u'll have the pro showing up.could b lambda sensors also,unless u check 4 faults first it'll b a guessing game which is time and money waste.ps; alws after replacing any sensor in the efi system a reset 4 the values must b done,or ecm will go havoc trying to adapt with the new values.if no faults are found which i doubt,that leaves u with badly leaking injectors especialy if car has a high mileage.now when it comes to lpg sorry i can't help,but if working good on lpg it means no faults there as i believe.
 
Jorjio has a point. After 2 years sat it would be worth cleaning out the MAF sensor with some carb cleaner, perhaps also the IAC valve (both very easy to do) and resetting the ECU adaptive trims to default. You didn't say why you changed the coolant temp sensor. How did you know it wasn't working? While the engine does try to run richer when cold it also will run richer at higher altitudes or in cold climates. Hence I suggest the MAF sensor and perhaps also the intake air temp sensor. Good thing is if you do decide to have the trims reset you can also have the faults read in the same session. One other thing in my exp (and I don't know the technical reason why), when the middle box of my silencer started to get clogged the engine ran richer and idled badly. Fitting a new box smoothed it out so check if your exhaust is obstructed in any way.
 
ROBV8 said:
It is single point yes, but why should that be anything to do with petrol running fault?


The maf sensor is a strong poss as I do get gearbox fault etc come up think that may be next call? Thanks for the help
Click to expand...

I had single point LPG too and upgraded to sequential injection. It's known that single point and p38 do not match very well.Mine was always perfect on gas but lumpy and very rich on petrol, i ran 10 years like that. Problem is that fuel trims are affected by LPG over the time and finally became out of limits. Then you need to reset adaptive values and run on petrol for 300 miles to make it run perfectly on petrol. I heard that it's because LPG is weak and single point isn't enough accurate so fuel management system richens to the max.
 
The reason I put coolant temp sensor in is because about 8 months ago I borrowed a snap-on scanner to detect a fault on my bros car, while I had it I plugged it into the range rover just to see out of interest if any codes were stored and it had coolant temp circuit fault on there. So when I had this prob I thought that was best place to start. I'll get the scanner and see if I can reset the values and check for codes again. I'll clean both sensors as suggested too.
 
You're not going to achieve reset of adaptive values with a universal scanner. You need either a Testbook or a Faulmate. Universal scanners only read and reset codes.
 
Right it's just been on a scanner and had coolant temp sensor and maf codes stored but as I had disconnected them last night I decided to clear them. I then attempted to start it and it fired on the button! So despite running bad last night it hadn't flooded? Anyway put it on live data and sure enough air flow=0! revved it and nothing. So to me that is suggesting the maf sensor is at fault? I disconnected it again while running and again it put the code up again. But no code comes up without me disconnecting it.
 
i may suggest driving the car for a few while before replacing the MAF,it has been sitting for a while,mine was sitting in a locked garage for 6 years lol,i couldn't believe the faults list i had,i drove it for few hundred kms,then rested the faults for 3 to 4 times,then guess what,no more faults,i didn't even replace any sensor,that's just me though.
 
You need to reset ECU adaptive settings to default. This is different from clearing error codes (sorry, just wasn't clear from your post if you did that). From what you write it does sound like the MAF is alive but not working well. Had you cleaned it? Can you borrow a known working one at the garage just to compare?

jorjio - lucky you! and goes to prove that contrary to what people say, P38s are not unreliable.
 
rasheed said:
You need to reset ECU adaptive settings to default. This is different from clearing error codes (sorry, just wasn't clear from your post if you did that). From what you write it does sound like the MAF is alive but not working well. Had you cleaned it? Can you borrow a known working one at the garage just to compare?

jorjio - lucky you! and goes to prove that contrary to what people say, P38s are not unreliable.
Click to expand...

My thoughts were that its alive as it registered a fault hen unplugged? I can get one for 68 quid so will prob just stick it on anyway. I haven't cleaned it yet so will remove it at lunch and try it first.
 
Last edited:
Don't get that chinese crap sold by Britpart. Those are well known to give worse results than a genuine one. I made that mistake last year. Clean yours with a contact cleaner but choose a spray that hasn't oil to lubricate or you'll mess the thing.
 
I also agree that the car needs a run at different loads etc before you condemn any sensor. Also, these (bloody expensive) things can be totally wrong but still not flag up a fault code..
Mine seems fine when driving but is giving the wrong signal out at idle, so replacement is on the cards.
Incidentally, I've found the best place price-wise for new MAF sensors is Euro Car Parts. They supply Bosch ones for a very good price.
 
if the problem continues i would suggest getting the ecu checked as i have recently just solved a very similar problem my car was doing exactly the same and after changing 02 sensor,maf etc etc it turned out that the ecu was faulty had it repaired and been good as gold defo worth getting it checked for £38 befor chucking a load of cash at it as i did lol
 
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