Throttle hesitation and overrun.

Sorry to be dragging this up again but the problem persists. I have run out of ideas. Please take a look at the short video above.

If I operate the accelerator or twist the throttle butterfly, the revs increase, obviously. But when I release, there is a very noticeable pause before the revs decrease again. I've replaced the throttle cable and tried disconnecting it from the throttle body, just in case. I have now thoroughly cleaned out the throttle body and fitted a new idle air control valve (IACV). I have reset the TPS. The air and fuel filters were replaced about 1yr ago (1000 miles). But none of this has made any difference.

Is this normal for a TF135? It doesn't seem right to me.

Does anyone have any ideas? Would a remap help?

I would have a look at the fuel canister next. This absorbs excess fuel and cycles it back into the system, maybe it is not working correctly and you are over fueling the injectors....then maybe the injectors themselves may be an issue.

Sundance

A remap may help. I talked to the Kmaps guy when he did my car last September and his map does sharpen the response of the throttle, so it goes up and down faster.

Have you tried contacting Jon Norris? He has hepled me before. send him a link to this thread he may have a few more ideas on how to sort your problem Bruce.

What is the idle speed sitting at when the engine is hot?
Should be 875 ish and steady. Does the idle speed wander?

SundanceUK wrote: I would have a look at the fuel canister next. This absorbs excess fuel and cycles it back into the system, maybe it is not working correctly and you are over fueling the injectors....then maybe the injectors themselves may be an issue.

Sundance

Fuel canister? That's a new one on me! Is it the black plastic thing you can see from the boot, close to the throttle body with a bunch of pipes coming out of it? I've always wondered what that is and what it does. Can it be tested/serviced?

Can the injectors be serviced in any way? This is the first fuel-injected car I've ever worked on!

David Aiketgate wrote: What is the idle speed sitting at when the engine is hot?
Should be 875 ish and steady. Does the idle speed wander?

Thanks for the reply, David.

The idle speed is 875 ish - always has been. It's rock steady. When cold, the engine starts at about 1500rpm but immediately drops to about 1100. Then it slowly drops to 875 as it warms up a bit.

Should I assume that this 'overrun' is not correct? The car drives fine otherwise.

That blows my theory out of the water. Never mind. I was wondering if the base idle was wrong, and the stepper motor was trying to fix it.
Difficult to tell on the video if that is unusual overrun or just normal.

Yes thats the fuel canister. Not sure if they are serviceable or not, but worth investigating. I have read some info on them in the how to's in the past.
The fuel injectors can be removed and cleaned, not done them on a TF but I have had them out on my KV6 engined ZTT. Just make sure you buy a seal or O Ring kit for the injectors and fuel rail before starting, as the seals would be best replaced when refitting, and just in case you damage any when taking the injectors out. I think they can be cleaned carefully, but to be honest for what they cost, if I was removing them, I would fit new and be done with it.

Good luck with the fault finding.

Sundance

SundanceUK wrote: …..the fuel canister next......

Charcoal canister,,,,,?

The way you show it on your video looks everything normal to me. You must put engine speed up to at least 3000rpm for approx 30 sec and than close trottle. Engine speed should than come down without hesitation or overrun.
While gear changing, MEMS keeps revs up to improve faster and smoother gear changing. Maybe that is your problem and must you to get used on this.
Just some idea but maybe helpfull.

Schrokke

Yes, I believe it contains charcoal.

I always had an intermittent slight hesitation when pulling away to the point it would sometimes stall. I found 2 things helped, firstly I hade the ECU remapped and that also improved overall performance. Secondly I found the throttle cable had a natural bend (upwards) as it passes across the rear shelf and that was being squashed down, flattened, by the sound proofing and plastic insert / cover so I cut a slot in the wadding underneath the rubber.