V8 3.9i Problem (driving me mad!!!)

[cookie55]

Hi, Got a probem with my V8 3.9i, It is a K plate Discovery left hand drive but is got no cats! And no signs of having any from new!!

When I first got the car it seemed fine but I never drove it as, it was damaged ( not hard) And been sat for a long time( few years) So I repaired it and started to make it my new off roader....... Got it all finished just about to take it for an mot and it would not start.. It would not even fire!! I tried a few things and found out it needed new plugs and fired up lovely.. Thought I had sorted it and took it out for a day and it seemed fine.. Parked it up and in a few days went to start it and the same happend again!! Everyone told me to put more new plugs in but I never did as I only just put new ones in!! I changed the dizzy/Air flow/ Cap/ Leads everything that I had spare, but nothing!! Chucked another new set of plugs in and it fired up!! Thinking I had a poo set of plugs and took it out for another day out!! Sure enough the next day it was running bad missing and choking up!! I tried to drive it to work and it died only a few yards up the road!! It seems to be over fueling loads... The plugs are jet black.. Even if I clean the plugs it doesn't work!! ( only new plugs will make it fire up) When its running it runs lovely!! So getting bored of buying new plugs ( tried ngk's and Denso Plugs) I got a mate that works in a toyota garage to get me some second hand plugs out of the service cars and chucked them in!! Fired up sweet.. I have had the timming all set up and changed the Fuel temperature switch! And found out it had no thermostat and put a new one in!! (thinking it was running to cold and telling the ecu lies) The car ran so much better and thinking I had sorted it I used the car for 3 days ( not miles ) and it seemed fine!! Till it did the same thing tonight!! I took a plug out and it was soaking wet and black!! I put a lighter on the plug and set alight to it and held it burning!!

I was told when I first picked the car up from the last owner that it had just been rebuilt!! As you never know what's the truth, but the engine does seem like it's been rebuilt with nice new shiney heads and new gaskets everywhere. The car has spent most of it's life abroad.

Has anyone had this problem???

Its driving me crazy!!

[Dave W]

With overfuelling like that I'd check the return pipe on the fuel injection, it's not uncommon for the return pipe to get blocked in the rubber sections as the inner wall collapses. A blocked or restricted return pipe will increase the fuel rail pressure resulting in over fuelling.

You say you've changed the fuel temperature sender, have you changed the coolant temp sender ? The fuel temp sender is much less important than the coolant as far as cold start/warmup is concerned. It's the ECU coolant sender that needs checking/changing, not the sender unit that is used for the water temp gauge.

If the above are OK then check the TPS, if that's OK then the airflow sensor would be next on the list.

[First_Fleet]

As ^^^^^^ but a suggestion that seems to have worked for a few people after I tried & reported it on mine.

Remove the Air Flow Meter multiplug.

Slightly twist the flat pins.

Clean receptacle AND plug with electronic contact cleaner. Allow to dry.

Inspect behind the rubber boot for loose or broken wires.

Refit plug & try again.

When this happened to mine, it ran just like that. That fixed it then, but much further down the track (apx. 2 years) the AFM was replaced but by then it was 12 years old anyway.

If you buy a pressure pack tin of contact cleaner, you can use the tube to get into the air bypass tunnel & give it a good burst of cleaner. NB **** Let it dry. You can do this carefully from the "engine end" of the AFM after removing it to a bench. Don't remove the inlet screen though as it's there for a good reason.

Do one thing at a time so you will know if you are on the right track.

[First_Fleet]

Double posted.

[Orange]

Have you also considered the ignition coil??

I had an issue with my Range Rover where I had sparks everywhere, along with flooded engine. Turned out that the spark wasn't big enough. I replaced plugs, leads, rotor arm and dizzy cap. It ran briefly, then coughed and spluttered before dying at 1am. The next morning (due to leave for Wales 2 hoursearlier) I called the RAC out to have a look and he said the sparks weren't big enough for a Rover V8. Plugged in the spare coil that I had in the garage and it fired and ran faultlessly...

Away we went without so much as a missed beat on a 500 mile weekend trip...

Worth considering.

[FridgeFreezer]

Should you have one to hand, removing the coolant temperature sensor plug & sticking a 200 to 400 Ohm resistor across the terminals should tell it the engine's somewhere around warmed up, if it then runs correctly you've got a faulty sensor. Mind you, for the £7 a new sensor will cost it's easier to just get one and fit it unless you have resistors to hand.

[cookie55]

With overfuelling like that I'd check the return pipe on the fuel injection, it's not uncommon for the return pipe to get blocked in the rubber sections as the inner wall collapses. A blocked or restricted return pipe will increase the fuel rail pressure resulting in over fuelling.

You say you've changed the fuel temperature sender, have you changed the coolant temp sender ? The fuel temp sender is much less important than the coolant as far as cold start/warmup is concerned. It's the ECU coolant sender that needs checking/changing, not the sender unit that is used for the water temp gauge.

If the above are OK then check the TPS, if that's OK then the airflow sensor would be next on the list.

Thanks Dave!! I checked the return today and that seem fine!! the one i changed was the coolant temp sender thats to the ecu!

I had it pluged in to day to see what faults come up on the computer!! It came up with coolant temp/ Air flow but only what i have been unpluging!! Cleared the faults and it did not bring any more up!!

All seems fine

Still running well rich