Throttle Jerkiness. Help!

[Prof]

Does the FD have the fuel pump resistor and relay like on the FC - this switches a resistor into the fuel pump circuit for idle, deceleration and light acceleration, as the pump does not need to feed as much fuel in these conditions.  It could be a dodgy connector or something in that area that\'s causing the hesitation - maybe bad fuel flow causing the hiccups.  On acceleration medium to strong throttle, the fuel pump gets full voltage, so the problem would dissappear.:3Confused

[RobEVo5]

exact/similar problem on mine - Where is the TPS. ?

Have had this similar problem on a MK1 MR2 and it was the TPS.

[RemarkLima]

I had something similar but very mild, and also found it would drop to correct smooth idle if clutched in from higher revs, but if you gave it a small blip it almost wanted to die... But found it was all caused by slack in the throttle cable, so I\'d come back on the throttle and it\'d pause a bit then hiccup forwards as the slack was taken up IYSWIM.

But I guess you\'ve checked this right? (pretty obvious)

If it was the O2 sensor then idle would also be dodgy as well as cruise. Can you reset the ECU\'s on these easily?

[RobEVo5]

Found the TPS...... back of the inlet manifold near the top. Tweaked it lunch time and feeling a bit better. Although as mentioned above, I think some of mine is a slack throttle cable as well, which will be sorted later.

[Andrew Harper]

Checked the TPS the best I can with a volt meter. And was within the ranges specified in the guide.

I do have a new throttle cable as the insulation on the old one was cracking. Haven\'t fitted it yet. There is a little bit of slack in the travel but not sure if this would make a difference.

I am doing the service at the weekend and weather permitting will change the cable at the same time. Will update then if anyone\'s interested.

[strange_days_uk]

Checked the TPS the best I can with a volt meter. And was within the ranges specified in the guide.

I do have a new throttle cable as the insulation on the old one was cracking. Haven\'t fitted it yet. There is a little bit of slack in the travel but not sure if this would make a difference.

I am doing the service at the weekend and weather permitting will change the cable at the same time. Will update then if anyone\'s interested.

very interested..

[stylus350]

Have to agree with Bobfish on this one and go with drivetrain slack as a possible cause.

[andysmee]

Thanks to this thread you have identified the problem I have. Basically when I am trying to cruise with little or no throttle the car kangaroos. This also shows on the Apexi in two areas; firstly the injector duty cycle only ever shows 0.0% or 5.0% or above, never anything in between, secondly, the apexi map monitor shows that when using the accelerator the car is jumping between load site 2 and load site 0 (i.e. not going through load site 1).
 
This is bound to be because the throttle pot (throttle position sensor above) is not set correctly for low throttle positions. Thanks to your help, and by using the Apexi I should be able to set this really easily, especially as I can lob the Apexi out of the passenger door and look at it whilst fiddling under the bonnet. Basically, I need to get the throttle to sit at load site 0 when closed and open correctly through load site 1. Bingo!

[Andrew Harper]

ok. thanks andysmee. let us know how it goes.

[RobEVo5]

Thanks to this thread you have identified the problem I have. Basically when I am trying to cruise with little or no throttle the car kangaroos. This also shows on the Apexi in two areas; firstly the injector duty cycle only ever shows 0.0% or 5.0% or above, never anything in between, secondly, the apexi map monitor shows that when using the accelerator the car is jumping between load site 2 and load site 0 (i.e. not going through load site 1).
 
This is bound to be because the throttle pot (throttle position sensor above) is not set correctly for low throttle positions. Thanks to your help, and by using the Apexi I should be able to set this really easily, especially as I can lob the Apexi out of the passenger door and look at it whilst fiddling under the bonnet. Basically, I need to get the throttle to sit at load site 0 when closed and open correctly through load site 1. Bingo!

Now there a different way orf tackling it :Thumbs-up .

In truth I think its a bit of everything, I have tweaked my TPS, and tightened the throttle cable and it much better now. Whats left is as stated about transmissioin slack.

[strange_days_uk]

Update -

After fitting an engine torque damper I have to say the car is almost cured.  The car is much more manageable in slow traffic and a noticably smoother gear change.

Get one !!

[Phil Bateman]

Is your air pump still connected ?
Before I fitted Apexi I disconnected mine and it was awfull in slow traffic - running rich at low revs.

Regards
Phil

[strange_days_uk]

I don\'t think it is no.

I am running single tub and full decat system..  But the car has always been a little lumpy since I first had it.

I\'m thinking that the engine mounts perhaps are finished..

[Andrew Harper]

Hello again,

Thanks Strange Days UK. Interesting that you say the damper almost cured the problem. Let me know how it goes over time.

I\'d read that if there\'s too much movement in the damper the bracket can crack the body work. But as I\'ve never seen a car with a damper fitted I can\'t verify this.

But I have thought about getting a damper for the car anyway.

Regards,

Andrew.