Sensitive throttle

[mike_msch]

No lights or OBD codes, but today the car hesitated up a not so steep hill. I was in 4th doing about 30mph. The car behaved like it was misfiring. Im guessing that it was hesitating as i was in the wrong gear. But what i noticed after was the throttle was very sensitive to a point where i could hold a continuous speed. The car jerked if i came off the throttle or pressed it again. The map sensor had Oil around it so i cleaned that. Just wondered what other sensors to look at. Also on occasions the revs go up a bit more than what they should  when i press down the brake and clutch to slow down. 

[Guest]

Hi Mike,

Diesel or petrol if the former what fuel quality do you regularly use?

Cheers,

Steve

[Mark Allen]

It is petrol Steve and thank you for responding.

[mike_msch]

Sorry, petrol awd. Im thinking that the misfire feeling going up hill is down to wrong gear and not enough rpm. But the sensitive throttle seemed a bit unusual to me. Almost like it wanted to either race or coast. Was a bit difficult to keep a constant speed. 

[Guest]

Hi Mike,

It may be worthwhile checking the Throttle Position sensor and the cable between it and the ECU - it would be worthwhile just to check, clean and lubricate (vaseline) the various cable connectors anyway - before anything else. If this is on the fritz then the ECU will be getting bad data that may cause the symptoms you're seeing. There could also be problems associated with the Throttle Body and its sensors so it would be worth checking these too - hopefully it will not be a faulty throttle body failure.

I'm surprised though that you're getting no OBD DTCs - are you using a Jag specific scanner?

Cheers,

Steve

[mike_msch]

Im using a cheap OBD reader from eBay. Seems to pick up codes when i remove sensors whilst the car is running. Its almost like the throttle is not reacting to me slowing down. My position sensor is riveted on. Some x types have a smaller one closer to the engine.

[mike_msch]

Update from quick drive. Does not show symptoms when out of gear, parked etc. My mechanic says its the computer re acting to no engine braking as the clutch is down. So it revs up a bit. Also my dmf has been rattling for some time, so a bit of unbalance can cause over revving. Plus my exhaust modification could of confused things and is flowing at a different rate that the engine is more responsive. Overall there is no concern unless a code is thrown up. Plus he said old cars dont play like brand new after 10 years.

[mike_msch]

Me be impatient i have spent the day under the bonnet. I have found what most likely is causing some over revving. One of my inlet manifold bolts has sheared. Luckily its the smallest bolt closest to the power steering reservoir. Two options, drill it out and replace with an oversized bolt or drill right through and use a nut and bolt to secure it. But also good idea to replace the others.