Thread: Severely Delayed Throttle Response - 2000 Disco 2 TD5 Auto

Originally Posted by carlosbeldia

I have a 2001 Defender with same issue. In my case, I did 4 things alltogether and it solve, so I don't know what was the error...

High / Low switch in transfer was put in High all the time
IAP cleaned (was as bad as yours)
Traced a short in the wiring loom that goes to the IAP at manifold, fixed with insulation tape
Disconnect the MAF

Never have had another bad response issue, sometimes it gets kind of slow but with only cleaning the IAP it goes perfect again.

Our high-low switch is definitely working

I cleaned the MAP. If the IAP is the same thing, I can't think what it would stand for.....Inlet Air Pressure? Inlet Ambient Pressure?

That reminds me, I have to check the wiring from the loom to the MAP...also from the loom to the MAF...and anything else I can find to check

We've tried disconnecting the MAF, but it made no perceivable difference If you simply reconnect the MAF you can tell instantly if that was the issue (if the delay returns).

Unfortunately we have to go out at 1pm, and I have a lot of preparing to do in the meantime so I may not get a decent chance to have another look at the Disco. I'll probably be working tomorrow, but I won't have to leave until 1.30pm, so I'll be able to try some things tomorrow.

I just went and checked all fuses. They're all fine. As I popped the bonnet it occurred to me that they were almost certainly all good anyway because we've had the delayed throttle as far back as I can remember and we've checked all the fuses often in search of a solution to the M&S lights (which HOPEFULLY have been fixed by removing the oil from the red ECU plug).

I also did a very quick check of the wiring from the MAF to the ECU and while I couldn't get to all of it without removing the engine cover I at least noticed one place where the bumpy plastic sheath had worn through, rubbing against the block. It's been taped up with electrical tape but it's not very well done and there's a chance the wires are bad inside, so that's something else to check tomorrow.

Unfortunately I think it must be something more difficult to fix than just a problem with the MAF, MAP or IAT, because I cleaned the MAP (no difference), unplugged the MAF (no difference) and unplugged the IAT (no difference). Surely if one of the those sensors were playing up, unplugging them would make a difference...?

David

Hello,
Other reason why the M&S light flashing is a low battery volts how good is your main battery ???
Ian

Originally Posted by justfishing

Other reason why the M&S light flashing is a low battery volts how good is your main battery ???

Thanks, but our battery is near-new. We replaced it sooner after the M&S lights came on, and had our alternator checked. It's all fine

If the MAF is recognised by the ecm as being out of range then disconnecting it would not make any difference so the cause could still be the MAF or faulty wiring to it. My TD5 had less heistation when disconnected because the MAF did not appear to the ecm as being faulty so was using the sensor results to set what it considered to be appropriate fuelling.

The only faults the ECU can detect with the MAF are signal below minimum and signal over maximum. The MAF can be reading anywhere between those two points and the ECU will treat the input as correct.

the sensor on the inlet manifold is the map/iat. Manifold absolute pressure/ inlet air temperature - the long part is the temp sensor, the hole is the inlet to the pressure sensor.
Cheers
Paul

Originally Posted by OffTrack

the sensor on the inlet manifold is the map/iat.

Ah yes, and the airbox one is the ambient air temperature and pressure sensor.

Originally Posted by Graeme

Ah yes, and the airbox one is the ambient air temperature and pressure sensor.

But only on the 15p's. 10P motors only had an ambient pressure sensor in the air box.

No points for guessing which well known diagnostic tool doesn't display AAT sensor data...

Originally Posted by Graeme

If the MAF is recognised by the ecm as being out of range then disconnecting it would not make any difference so the cause could still be the MAF or faulty wiring to it. My TD5 had less heistation when disconnected because the MAF did not appear to the ecm as being faulty so was using the sensor results to set what it considered to be appropriate fuelling.

Originally Posted by OffTrack

The only faults the ECU can detect with the MAF are signal below minimum and signal over maximum. The MAF can be reading anywhere between those two points and the ECU will treat the input as correct.

Ah, now I understand. I was confused because my thinking was that the hesitation should go away if the MAF was disconnected, as the ECU knows immediately to use its defaults (open circuit), but of course if the MAF is already fully broken (out of range) or if there's a broken/shorting wire (open circuit or short circuit) then the ECU would be already using its default-mapped settings. The thing that confused me was that I assumed default settings would remove the delay, but of course if the default settings are inadequate for the current air flow (like if you've just stomped your foot) then the delay will be present.

That's excellent, because we might be going down to Alstonville and Ballina today, so I might see about getting a new MAF. Do you think a LR mechanic would be happy to let us borrow one and test it?

Thanks for all your help, guys

Originally Posted by OffTrack

the sensor on the inlet manifold is the map/iat. Manifold absolute pressure/ inlet air temperature - the long part is the temp sensor, the hole is the inlet to the pressure sensor.

Originally Posted by Graeme

Ah yes, and the airbox one is the ambient air temperature and pressure sensor.

Originally Posted by OffTrack

But only on the 15p's. 10P motors only had an ambient pressure sensor in the air box.

Thanks, now I know what they're all correctly called I assume when you say 10P and 15P you mean number of ports?

Originally Posted by OffTrack

No points for guessing which well known diagnostic tool doesn't display AAT sensor data...

lol