Thread: 93 Disco V8 Idle Problem Again/Still

Hi I had a similar problem and tryed what you havedone to no avail but found out it was my TPS(throttle position sensor i think that what its called?)my butterfly in the throttle body had spun to far back and stuffed the little bugger zacc

Could be bad contact on temperature sensor/bad sensor.
Bad thermostat , letting engine get under 80c when the ECU richens, ie "choke"
Maybe bad TPS , but TPS is usually a "flat spot" or inexplicable cutting out while cruising.
Richness is NOT caused by stepper. The stepper only lets a bit more air in to increase the idle for cold start or compensation for aircon.
Regards Philip A

I have posted a few times previously on this subject as it was driving me bonkers & to me was spoiling the Discovery experience..

I don't know the 100% fix but this is what I did on mine over a period of a couple of years.
Each one "seemed" to improve it a bit, when now it hasn't misbehaved in months. In the order of replacement.

1. Replace IAC valve, after setting up the pintle to specified dimensions.

2. Replaced EFi Coolant Temperature Sensor.

3. Replaced dizzy Vacuum Advance Module. (was leaking)

4. Replaced ALL Plug leads inc. coil lead.

5. After the previous non genuine IAC snapped off at the thread (bad manufacture) I removed the plate that it screwed into to remove the broken thread.
Lo & behold, the Allen Screws were loose-ish & needed little pressure by the key to undo.
Plate actually could be slid around minutely on the engine.

New gasket & a smear of blue sealant later, back it went nice & firm.
I had never needed to remove this before & quite honestly, hadn't even tried to nip up the screws.

Now it achieves the recommended Idle setting ie. AC on/off, starts & idles as it should, hot or cold etc.
Very occasionally & I mean hardly ever, the idle stays up above 750 for a minute or so & then drops back to 725rpm for some reason, but I have just put that down to the ECU or something calling for this speed as part of the anti pollution sequence. (one reason V8i's idle faster than a 2.25 Series donk @ 500 rpm, I believe)

Recently, in an effort to try & cover all practical aspects even though it was idling like a good 'un, I removed & cleaned (after busting ) the Vehicle Speed Sensor/Transducer on the back of the Transfer Case.
I think it fell to bits rather than me busting it & if you Google re Discovery Vehicle Speed Sensor or similar, coming apart seems to have been a problem with them. (plenty there).

P/N was AMR1253 & now superseded to YBE100540. Maybe this was why it was superseded??

As it appeared open to road dirt & general crap, it appeared to have a collection of magnetised particles gathered in the magnet chamber.
You would not normally be able to see this if it was in one piece, but it seems to let go at the joints in the plastic cover.

I resealed it back together with blue gasket silicone & couple of small cable ties & it seems fine for now. Come to a stop & idle comes back immediately.

I had requested (twice) a price for a replacement, but like DM on here, find some places just don't reply. At a guess, it would probably be over a $100. A UK price was 32 GBP + PP.

Apologies for the diatribe but my experiences may be useful to some.

I just had a thought on Tank's problem.

I guess my questions are
1 Did you have a full tank?
2 Did you go up and down very steep hills?
If the answer to both is yes then the problem is probably that you drained some fuel from the tank into your carbon canister, and then either rich vapour or raw fuel was pulled into the inlet manifold by the normal purging process.
This would explain why the problem went away as the petrol in the canister was exhausted.
I have had this happen to me in a Suzuki Vitara.
Worries you at the time but is no long term consequence and really not muchcan be done.
Regards Philip A

Originally Posted by PhilipA

I just had a thought on Tank's problem.

I guess my questions are
1 Did you have a full tank?
2 Did you go up and down very steep hills?
If the answer to both is yes then the problem is probably that you drained some fuel from the tank into your carbon canister, and then either rich vapour or raw fuel was pulled into the inlet manifold by the normal purging process.
This would explain why the problem went away as the petrol in the canister was exhausted.
I have had this happen to me in a Suzuki Vitara.
Worries you at the time but is no long term consequence and really not muchcan be done.
Regards Philip A

Thanks all for the info, it gives me some more things to check out, will keep you all posted, Regards Frank.