3.9 EFI Ramdom stalling CALLING ALL EFI EXPERTS!!!

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bendelaurence

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234
Hi,

Ive just finished installing hotwire efi on my 3.9. I've got it running with all the sensors except for the speed sensor. I'm not using lambda sensors or cats and have changed the tune resistor accordingly (470ohm).

She starts, idles and drive perfectly. Very happy so far.

Just one problem to solve......

If i leave it idleing, it will run and run and run, then all of a sudden the revs will drop. The ecu rescues the stall then immediately the same thing happens again and eventually it dies. Also when pulling up to a roundabout or similar, when i pull the clutch in it will die on idle.

My thinking so far is that its not the MAF. Am i right in assuming that if the MAF was faulty it would have this problem continuously?

It doesnt seem to be the coolant sensor because it does exactly the same with it unpluged?

I'm stuck to be honest.... What's bugging me is that it runs fine for a good while before the trouble starts, and then can run fine strait after..

Any ideas people?
 
The speed sensor on the donar vehicle doesn't fit my transfer box. The transfer box seems to be different. Mine has an analogue speed gauge with an anolog cable. I wonder if they an electronic sensor that will replace my cable?

Both the base idle and the airflow meter bungs have been removed prior to me which suggests that they have been tampered with in the past. I found instrutions for base idle but how do I adjust the air flow?

I'll recheck connections again.

Thanks so far
 
you need to get the speed sensor in mate, mine used to do exactly the same at roundabouts, and i found that my speed sensor had a broken connection inside.

im not sure if you can pull out the electronic speed unit from the transfer box and fit the analogue cable fitting. i dont know if the box itself is the same. AFAIK the electronic unit will pull out, amybe the cable fitting will too.

there is no crossover though, if you wanted electronic speedo you would have to fit later speedo pod too etc etc.
 
do a search for airflow meter trim, I cant remember exaclty but you need a multimeter and i think but am not sure its 0.30v on the outside two pins on the plug with a mulitimeter
 
Mr Noisy said:
you need to get the speed sensor in mate, mine used to do exactly the same at roundabouts, and i found that my speed sensor had a broken connection inside.

im not sure if you can pull out the electronic speed unit from the transfer box and fit the analogue cable fitting. i dont know if the box itself is the same. AFAIK the electronic unit will pull out, amybe the cable fitting will too.

there is no crossover though, if you wanted electronic speedo you would have to fit later speedo pod too etc etc.
Click to expand...


I've no problems dumping my anolog speedo, I just ne to find a speed sensor that will fit my transfer box. I'll make some calls in the morning. You must be able to get an electronic sender that fit where my old speedo cable used to be......
 
fett said:
do a search for airflow meter trim, I cant remember exaclty but you need a multimeter and i think but am not sure its 0.30v on the outside two pins on the plug with a mulitimeter
Click to expand...

Really is it that easy? That's good I thought I'd need to stick an emission tester in the exhaust to do it. Is it the for motors without lambdas like mine?
 
What I'm saying is mate, the 200 disco is a cable, the 300 is a electronic speed sensor, for ECU and speedo.

Im pretty sure the transfer box is the same, I think the cable receiver is pushed into the transfer case, and when removed can be replaced with the electronic unit. As far as I know anyway!
 
Mr Noisy said:
What I'm saying is mate, the 200 disco is a cable, the 300 is a electronic speed sensor, for ECU and speedo.

Im pretty sure the transfer box is the same, I think the cable receiver is pushed into the transfer case, and when removed can be replaced with the electronic unit. As far as I know anyway!
Click to expand...

I get ya! I think you're right. I found this Electronic Speedometer Replacement which is what u said along with model numbers. Best get ordering.....
 
fett said:
its the meathod used for mine without lambdas, is easy if you know it :D
Click to expand...

Ok, i did what it said here:

POAH said:
does it have CATS? or is it pre 92.

if its running ok on gas then its likely not to be a spark issue. fuel delivery to those cylinders could be a problem.


are all the plugs soaked or just a couple?

to check the AFM on a non cat car.

Blue/Green Air flow signal- should be .2-.7 volts (no air flow). Tick over on the 3.9 is about 1.7 volts

Blue/red CO trim value. This is factory set 1.8 volts for catalyst engines, although I believe this setting is ignored with Lambda correction. Non cat cars are in the range of 1-1.5 volts, although accurate setting will require the use if an exhaust gas analyzer

Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Click to expand...

I got 2.5v!!! Time for a new MAF?? Any ideas of the cheapest place for them? I dont want a used part because its likely to be another nakered one....
 
ebay is cheapest for a new one at about £50 but I dont now about the quality, probably made in an indian back steet.

used ones can be ok , check they dont rattle lol

genuine new one is £1300 form landrover, yes £1300 no joke :doh:
 
£1300!!!! There must be some kind of reputable replacement? I've beenm looking just now, but i'm drawing a blank. Seem to have loads in the US...... hmmmm............
 
it wont do the bores any favours washing the oil out of em like that.

will be ok for a little in the snow but not ideal.

I bought a used one as spare and have run with both, they are good.

a new non landrover one from a motorfactors is £280 I think. I would try the £50 new ebay job!
 
Do a search on here for 'maf test'

I wanted to check mine out a few weeks ago (just decided to make sure it was healthy) and I searched and found a few good posts quoting the resistances needed for a good unit.

Thus, if you take a multimeter to a scrappy, you will hopefully be allowed to test it before buying it.

Hey ho :)
 
I've ordered a Fuelparts replacement MAF, it's costing about £160. I'll let you know how I go with it. I nearly bought the £50 eBay one, but I just don't trust it...... If anyone does decide to try one I'd love to know the results. :)
 
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