Thread: Running Rich

Originally Posted by Utemad

I've never disconnected mine with the engine running. Only started it with it disconnected (forgot to reconnect it). It blew smoke from the exhaust til I stopped and reconnected the AFM and restarted it.

Maybe that is different to disconnecting it with the engine running as I know mine works.

Same thing,When it is not connected it gets told to put in more fuel.Yours is working if thats the case

Mine was doing the idle shake at lights, occasionally stalling but never missing under load...
My mechanic plugged in his gizmo to the exhaust and the readings were sky high, and could not be adjusted down. He reckons I was spitting pure petrol out the back. Dead MAF. Reco / exchange MAF and a bit of adjustment and all is well again.

Does anyone have any experience of a throttle ptentiometer failing?

My RR'90 3.9 is trying to burn riduculous amounts of fuel at idle. Black smoke at exhaust, sooted plugs. Revs freely and with gusto. Phut phut at tail pipe. Rough idle and any sustained revs (only up to 2.5k). Ignition system checks out OK (Slight 'out of round' of top section of shaft so that reluctor air gap is not constant). Spark at all plugs. New plugs, leads, dizzy cap and rotor.

Pulled fuel rail and injectors off and tested while connected to wiring harness. No leaks while under constant pressure (connected terminals 30 & 47 at relay connector for pump with relay out). Cranked motor to check operation of injectors while still out. All operate though noticed unusual behaviour with number of injections/engine revolution. Sometimes the injectors operate roughly in number with the cranking revs (85rpm against compression), other times (starting with a new crank event) injectors seem to operate at twice the speed. I assume the latter is occuring when the injectors are installed given the aforementioned symtoms.

While stepping through the Haynes EFI trouble shooting section I tested the throttle potentiometer. Ohms read in range at 5,500. Volts reading with throttle closed reads 9.6V. Thottle fully open reads 5.5V. Should be 0.1V with throttle closed?

Background: Recently had an engine fire! Seemed to start near fuel inlet/outlet hoses. Extinguisher did't work. Fire burned for approx. one minute. Melted most hoses around top of engine as well as destroying wiring harness and most sensors including air flow meter. Main fan and cowling were also damaged beyond repair. British Off Road in Brisbane sent me some used parts up here in Nhulunbuy NT (remote) at the right price. I would have had to write her off otherwise (Thanks Rob).

Has anyone else had a similar experience with the throttle potentiometer?

Originally Posted by Rangie90

My RR'90 3.9

While stepping through the Haynes EFI trouble shooting section I tested the throttle potentiometer. Ohms read in range at 5,500. Volts reading with throttle closed reads 9.6V. Thottle fully open reads 5.5V. Should be 0.1V with throttle closed?

Haynes manual ... Page 13.38 .... paragraph section 122

Reads as the following

Ohms with in range of 4000 to 6000

Volts reading with throttle closed = 0.085 to 0.545 Volts
Thottle fully open = 4.6 to 5.0Volts



Your readings show that it is shorted out which = rich fuel mix, which = ECU in limp mode

Test the wires leading to it, then buy a new / second hand unit
You have to calibrate the throttle potentiometer when installing it (voltage test / tune)


Mike

Volts reading with throttle closed reads 9.6V.

Seeing the TPS only has a 5volt feed, I believe that you have misread 0.96 volts as 9.6 volts.
This is near enough to be OK.
The issue with a TPS is whether there are any gaps in the continuity of voltage increase with throttle position. the way to test is to gradually open the throttle and check that the voltage increase is smooth and the best instrumenty is an analogue multi meter which are now like hens teeth.
Regards Philip A

Hi all,

Looks like my MAF sensor is jiggered too. The little screen on the front has a dozen broken connections too it, I suspect, having never had one out of the car before that that screen is the "hot wire" and it needs all the wire to be connected.

So I disconnected it when running and no change, still rough, mine actually stalls sometimes and to restart it I have to wait five minutes and sometimes have to hold down the throttle after just like you have flooded an old carby car. The hesitation and stalling happens after it gets warm, which makes me think that the car is running rich when cold (a good thing) but is too rich when it is hot and starts spluttering, and even cutting out (sometimes in very awkward places).

Now, my understanding is that when the MAF sensor is not in place, then it should shut down, so why doesn't it when the MAF sensor is faulty? That would indicate to me a broken wire in the loom to the injectors.

Anyway, your thoughts would be much appreciated. BTW I have cleaned and checked everything before looking at the MAF sensor in the hope that it was just a cleaning/loose wire type of problem.

Thanks again.

Greg

Originally Posted by bigmac2x2

Hi all,

Looks like my MAF sensor is jiggered too. The little screen on the front has a dozen broken connections too it, I suspect, having never had one out of the car before that that screen is the "hot wire" and it needs all the wire to be connected.

Greg .... No ... The stainless steel mesh is just a airflow screen // If you take off the large outer circlip off to release the screen from the MAF body

// behind the screen is a 6mm hole to the side ... shine a torch in it and you will then see the "Hot wire" ... It looks like a light bulb "filament" (2 wires with a coil between) This is what you clean with "Circuit board cleaner" (A spray can with the extension tube)

Do this and see the difference

Then Pull the plug off the motor Temp sensor for the EFI .... and test the Ohm's when cold & then when Hot .... Use the Haynes manual to locate it

Plenty of other areas to check ... if this proves no results

Mike

I have the same issue with my disco... It's driving my crazy. The story so far (all too familiar!) goes like this:

Had my disco converted to gas... gas installers put on a terrible DIY air intake-pipe that disconnected after a few days... disco backfired regularly... Something died... led to awful spluttery idle Therefore the ECU thinks too much air is coming in so it runs rich - same old story so many of us share....

This happened about a year ago - since then I bought a brand new rover intake pipe and the car ran okay on LPG (except for a slightly high idle) but runs on limp mode on petrol (blowing black smoke and always feeling like it's going to stall).

Anyway, long story short - today I pulled out my black-gunk encrusted stepper motor and cleaned it thoroughly and installed a brand new MAF from ebay. STILL no fix to the rough idle on petrol!!!

When I disconnect the MAF while running it makes no difference - but when I disconnected the stepper-motor (before I cleaned it) the idle increased and became more constant (about 1500-2000rpm) - I've checked the MAF wiring and it all seems good. I'm thinking about biting the bullet and taking it to a good Rover mechanic - but in the meantime I'd like to continue my own trouble-shooting...

I know everyone may be tired of this story - but any ideas?

Cheers,

Damian.