My jaguar X-Type moves along in 1st gear as if I have my foot on the accelerator, but it's not. I don't believe it's the cruise control as this dosent kick in at 5-10mph. If I brake it stops for a while but soon returns. Nothing has come up on diagnostic check. Any ideas would be appreciated.

 

Jaymo, I guess I have a few questions:

1) is this much more pronounced when the motor is cold?
2) when you say it is moving too fast, how fast are we talking? My X-Type would idle at about 10 mph without my foot on the gas when on level ground.
3) when in Neutral, what does the tach say your RPMs are?

When the car is cold, the ECM will artificially raise the idle to help the engine warm up which will cause the car to "idle" faster and therefore cause the car to move down the road faster than when the motor is warm.

If you see that your idle is higher than normal when in Neutral, it may be possible that your throttlebody is sticking partially open and the ECM is adding fuel as necessary to maintain the proper air/fuel mixture. Granted, if this is too bad, it will throw a code for a mismatch between the gas pedal and the throttlebody position.

 

Thermo
I will be off work Thursday so will check all this then and get back to you.

Thanks

 

I don't think you have a problem at all. If you let the clutch out on any car and take your feet off the pedals, they are all going to move along at this speed.

 

Topanga
Thanks for that, but I've been driving for 40 years so i know its more than just that. There is an issue. Just need to find out what it is.

 

What's the idle RPM in neutral? I'm assuming you've got a manual transmission.

 

Around 795 …-800

 

It ain't high idle RPM then. I think you've got normal operation.

 

Jaymo, from the sounds of things, your idle is right about where it should be. Just to ask another silly question, does things change if you park the car, apply the e-brake, then release the e-brake? If yes, what you may have been experiencing is a dragging caliper and if you notice the car idling down the road faster after having not used the e-brake for a few days, you really have a problem when the car is going too slow (ie, dragging caliper).

 

I have recorded a 2 min clip of the issue I have of car moving along at 9mph with no acceleration. It is this that does not feel right. I would expect it to be about 4mph . I did another test this morning which was pretty cold, frost symbol showing on dash. Today it ran perfectly and this is the first time it's done that for ages. Crept along at 4mph.

Here is this mornings vid

 

Maybe have a look at idle fuel trims. If there's a small air leak it'll produce more power as it has to correct for the extra air.

Would help to know which engine!!

 

Sorry I thought I had added engine etc to profile. I'm not used to using Forums.

It's a Mondeo 2ltr Desiel in a manual X-Type 2004

Someone who watched the video said it could be throttle body valve that needs cleaning so I'm looking for YouTube video to look at that, but not come across my model yet.

 

Watching the 2 videos, there is one major difference I see. In the first video, the car is shifted to 2nd gear where the second video, the car remains in 1st. This in itself would explain the speed difference. Keep in mind that with the electronic systems of the car, they are going to attempt to maintain the idle at a constant number. So, with the car being in a different gear, the speed will be different as the throttlebody is being opened by the computer to maintain the desired RPM (in this case, 950 RPM). Now, if the car is maintained in the same gear (say 1st) and there is this difference, then yes, this would be a problem. Since there is no device that slips (like the torque converter in an automatic tranny) in his car, that would mean that the engine RPMs would have to be up at 1900 RPMs in 1st gear to maintain 9 mph. The only other way to have a difference (ie, both cases being in first gear, 950 RPM, but 2 different speeds) is to have slippage in the clutch (in this case, no slippage would be the 9 mph and with the clutch slipping would be 4 mph). Please keep in mind that transmissions are not my strong point and there may be something I am missing here.

Like was mentioned, if the throttlebody is sticking, that would allow more air into the engine and at this point, the ECU would admit more fuel to keep the air/fuel mixture correct, resulting in effectively the gas pedal being stepped on. This would result in raised engine RPMs and therefore a higher speed. I had a similar issue with my petrol powered truck and a cleaning of the idle air control (IAC) valve resulted in the problem being corrected. With the Jags, they actually crack the throttle open slightly to do the same job as what the IAC valve did on my truck.

 

Thanks for such a comprehensive reply . I will test the car over next week to see what I get.

Thanks for the response, I'm grateful

 

So I retested the car this morning and I came to the conclusion that in first gear, the car acts exacty as it should. Revs around 8000 idle. Car then creeps along in first gear at around 4mph. BUT when I go into second gear and touch accelerator it's fine until Itake foot off, the car then will drop back to 9mph rather than 4mph which is far to fast for short roads with turnings. So it seems the problem only occurs once I accelerate above 1st gear.

 

jaymo, I want you to try something. Find a road that you can drive whatever speed you want. Start the car and leaving your foot off of the accelerator, get the car rolling in 1st gear. Let it get up to the 4-5 mph. Now, shift to second gear. Paying a little bit of attention to the RPMs (make sure not to hit anything), do the RPMs remain the same (ie, around 950 RPMs) and the car accelerates up to 9 MPH? If so, then the car is doing what I mentioned before in that the computer is trying to maintain the 950 RPMs. You may see the RPMs go up to say 1100 or even 1200 RPMs and down to around 600 RPMs as you are letting out on the clutch as the ECU is fighting to maintain the RPMs at 950.

If this is what is happening, to me, the car is acting just like it should. If I remember the manual tranny gear ratios right, 2nd gear is approximately twice what 1st gear is, which would explain why you are seeing 4 mph in 1st, and 9 mph in second. Granted, it probably would not hurt to pull the intake tube off of the throttlebody and using a rag, spray some carb cleaner on the rag and wipe out the internals of the throttlebody. Pay special attention to where the butterfly valve touches the throttlebody. If you have build up there, it can cause things to stick and give you random problems.

 

Thermo, thanks for that advice. I live in a built up area so will have to try find somewhere I can test this. The problem is not that it goes up to 9mph, the issues is that it will not drop back down in speed. So I think it could be the valve sticking. When I'm next off for a few days I will take it off and clean it.

 

Hi I have watched this post with interest but am still confused.
Are you "the OP" expecting your motor to travel at the same speed ie 4mph at idle in second gear as it does in first? My x type is exactly as yours, 4 mph in first and about 9 in second. If it would pull this speed I would expect around 15mph in third and heaven forbid around 35 mph is 6th.

Or have i got it all wrong?

 

The issue is not that it goes up to 9mph in 2nd, the issue is that if I brake to take a tight corner the car dosent slow down, it stays at 9mph. So it's like having your foot on accelerator and brake at same time.

 

OK I understand now. But if I braked at tickover in second gear my car would stall. unless I dipped the clutch.
I would expect the engine to fight you if you try to drop it below tickover by braking, it's trying to maintain that 800 revs,
surely the correct action is to change down or dip the clutch "which is bad practice."