td5 acceleration delay

Coincidence or not? If I disconnect the MAF on my '03 TD5 Disco then start the engine hot, it will idle forever, but when I go to take-off there is almost no throttle response (just enough to get me out into traffic) for about 5 seconds, after which the engine jumps to life and works well. I assume it takes about 5 seconds for the ecu to decide that the MAF is non-operating before reacting to the throttle position.

The TD5 MAF can give significant incorrect readings that aren't recognised by the ecu as errors and therefore no fault code is stored. I've encountered dangerous delayed throttle response (causing the vehicle to slow after opening the throttle) on a 99 TD5 Disco that was fixed with a new MAF without any codes ever having been recorded.

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Originally Posted by Graeme

Coincidence or not? If I disconnect the MAF on my '03 TD5 Disco then start the engine hot, it will idle forever, but when I go to take-off there is almost no throttle response (just enough to get me out into traffic) for about 5 seconds, after which the engine jumps to life and works well. I assume it takes about 5 seconds for the ecu to decide that the MAF is non-operating before reacting to the throttle position.

The TD5 MAF can give significant incorrect readings that aren't recognised by the ecu as errors and therefore no fault code is stored. I've encountered dangerous delayed throttle response (causing the vehicle to slow after opening the throttle) on a 99 TD5 Disco that was fixed with a new MAF without any codes ever having been recorded.

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This can happen, sometimes it will not log a fault if the MAF is faulty, what i did was clean it with Carby cleaner and it was OK after that, try that before you buy a new one, electrical contact cleaner is best and don't touch the element with anything but the cleaner.

Baz.

I have tried a new maf and it didn't fix it, but i now find if i disconnect the aap sensor on the airbox lid it fixes it and doesn't do it again. could i be masking the problem or is it likely to be this? Thanks for all your input everyone! Rat.

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Originally Posted by DEFENDERZOOK

thats what it sounds like to me too......turbo lag....
when you are cruising the turbo dumps the excess boost....
when you floor it.....it needs time to build up boost again....but needs a lot more boost due to the higher revs/speed....?
hence taking a bit of time to spool up.....?


or possibly a sticky valve somewhere such as waste gate.....?

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At 100km/h flat cruise its already boosting at 10-14psi reaction time is almost instant.

MAFs can present issues without showing codes, borrow someone else MAF and go for a blast, or disconnect the maf wire and run in default mode. You sure the connectors on properly and hasnt worn a wire through somewhere (has happened).

The turbo doesnt bleed serious boost until around 16-19psi, so this shouldnt be the issue.

Cheers
Tombraider

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Originally Posted by Rat

I have tried a new maf and it didn't fix it, but i now find if i disconnect the aap sensor on the airbox lid it fixes it and doesn't do it again. could i be masking the problem or is it likely to be this? Thanks for all your input everyone! Rat.

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My AAP sensor failed, causing excessive fuel consumption etc..

replacement cost shocked the crap out of me....

Borrow one to be sure!!!!

Cheers
Tombraider

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Originally Posted by tombraider

My AAP sensor failed, causing excessive fuel consumption etc..

replacement cost shocked the crap out of me....

Borrow one to be sure!!!!

Cheers
Tombraider

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Dont want to high jack but what's the AAP sensor?

I think it measures Ambient air pressure for different altitudes and then the ecu can compensate by changing fuel mixture and timing. When my car plays up, it gets the acceleration delay as well as the fuel economy goes to sh*t. Today I cleaned the sensor with electronics cleaner and it still played up from cold start, but not from hot start. Once it is disconnected, no problem.

Tombraider, what symptoms did yours do with it's faulty aap sensor?

Rat:twisted:

My 2003 TD5 manual Disco developed a throttle delay of about 3 seconds in Aug 04 that initially was only at lower altitudes/higher temperatures even on the 1 drive, but it soon became permanent. The AAP sensor was the 1st sensor I had swapped (from another vehicle that may have been an auto) but that didn't make any difference. The MAF has since been replaced for other reasons. I replaced the MAP sensor and it made an improvement but didn't fix it totally. EGR/ILT are usually unplugged as this makes another minor improvement. It doesn't occur with the MAF unplugged, but fuel economy goes out the window. Even with the MAF connected, it gets better fuel economy at 115 than 110, as the problem doesn't occur past about 112. Tomorrow I will unplug the AAP sensor and see what happens. I'll soon know, because it happens as soon as the temp gauge starts moving.

Unplugging my AAP sensor didn't make any noticable difference to my vehicle today. I didn't try a freeway run, but the normal throttle delay was still quite evident as usual when it warms-up.

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Originally Posted by Graeme

My 2003 TD5 manual Disco developed a throttle delay of about 3 seconds in Aug 04 that initially was only at lower altitudes/higher temperatures even on the 1 drive, but it soon became permanent. The AAP sensor was the 1st sensor I had swapped (from another vehicle that may have been an auto) but that didn't make any difference. The MAF has since been replaced for other reasons. I replaced the MAP sensor and it made an improvement but didn't fix it totally. EGR/ILT are usually unplugged as this makes another minor improvement. It doesn't occur with the MAF unplugged, but fuel economy goes out the window. Even with the MAF connected, it gets better fuel economy at 115 than 110, as the problem doesn't occur past about 112. Tomorrow I will unplug the AAP sensor and see what happens. I'll soon know, because it happens as soon as the temp gauge starts moving.

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Maf's, Map's, aap's, sensors of all kinds, ecu's emc's, rubber bands, turbos, electronic things that go fizz in the dark. Aren't I glad I've got a County-Isuzu with mechanical injection, and without un-necessary things that stop working but cost lots of Oxfords and lots of stress.