2001 XKR, 75K miles

Getting some pretty recurring and substantial hesitation in throttle response while pulling away from a slow / stop, seemingly only in sport mode / first gear. Car will barely pull away, then bog down like a safety cutout, then suddenly re-engage and take off. Goes on for 0.5 - 3.0 seconds, and a few times I've been able to floor the pedal with no response. Ouch.

Car has been having ABS / Trac warning on and off for a few months, but without the throttle lag. Once or twice the lamps have gone off fleetingly during the throttle problem, but not at all consistently and if so they don't remain lit. If the ABS / Trac fail come on it's usually at some random time while driving.

I haven't yet cleaned the wheel sensors yet and I likely need to open the module to check soldering, etc. The usual stuff it seems... But in my reading I don't see many people experiencing this substantial throttle lag in conjunction. Doesn't feel like the trans is slipping, and it is full of new-ish correct fluid.

Thoughts?? Many thanks.

 

Cafe racer, as I read your question my thoughts zoomed right into the effect of TRAC CONTROL.

What I mean is, it drove me crazy for a while after purchasing my XK8 that has Trac control on off switch (as opposed to DSC on off).

Why I wondered would the car hesitate so much on left turns with WOT? She was compensating for bloody wheel spin!

Turned off Trac Control button (LED lights) and all was fixed! Sure, she did spin the wheels but now I was getting 290hp to the wheels.

Now you described straight line accelerating but the symptoms are the same.

Right after thinking about the similarity you mentioned issues with ABS and Trac warning. I'd sure put this at the top of my troubleshooting list.

BTW what happens if you turn Trac OFF?

Let us know.

John

 

Good question -- if the ABS / ASC or just ASC lamps are on, orif the Trac Off is manually engaged, then the problem seems to go away. So I imagine the module is the problem -- it just doesn't consistently put up failure warnings when the hesitation occurs, which makes me wonder.

 

Happens to me all the time in my 02 xkr. With traction control on, acceleration around a corner significantly curbs the grunt until the module says, "all is well." It's rather disturbing when you are trying to merge!

 

It may only be supplementary to your complaint but might also be worth checking your throttle cable adjustment.

 

would add that you should make sure there are no block air leaks as depending upon the RPM when you initiate your acceleration, fuel trims can affect your acceleration. air leaks will change these at idle and other low RPM ranges.

 

Could you say more about finding and fixing such leaks...?

 

I think whitehat is saying check the tube running from the air filter box to the throttle body (cracks and leaks on bottom side) if you suspect, use duct tape till you can get a new one. Also check the gasket for the tube as it sits on the throttle body, both of these are after the MAS sensor so the computer cannot adjust for the extra air.

 

there was a recent thread addressing this issue. simply search this sub forum for fuel trims and the most recent discussion thread will give you a lot of information.

 

Essentially, OBDII tool (e.g. elm327) and look at LTFTs (and if you like STFTs).