Hi again. I'm still chasing running problems on my 1999 2.0 and had the OBD scanner on the car checking throttle position %. With the engine running unless you take the throttle well up you just get 0% all the time. Interestingly if you switch the engine off and operate the throttle up and down quickly the throttle position is shown (probably correctly) until the ECU shuts down. This to me suggests that the position sensors are working and reporting the position correctly but why doesn't the position show with the engine running, is this an ECU fault or is the engine running in limp/get you home mode and therefore the throttle position is not being read or used by the ECU and therefore not shown as other than 0% to the OBD socket? The symptom that has me chasing faults here is throttle hang when you take your foot off the pedal, return to tickover is slow, tickover is good and smooth. It's cable operated and is adjusted and working okay. No air leaks and oddly no fault codes are present.
Throttle Position
- Thread starter kingsgate
- Start date
is this not normal? mine does the same when driving and untill the car comes to a complete stop the revs stay just over the 1000 rev range. is this what you are talking about?
No I don't think it's normal, showing my age about less complicated engines when you 'blip' the throttle the revs should fall back to normal tickover quite quickly, on my Z3 they don't, the revs hang and drop back to tickover after a seond or two, no matter how far up you take the revs the effect is the always the same. On a sporty type enging like this you'd expect to be able to blip the throttle on downward gear changes but not on my engine the revs just don't drop quickly enough to allow that. I'm becomming more suspicious that I have an ECU problem, I have more then one electrically related issue and from what I can tell they seem to have one thing in common, the ECU. In your case you may have one of the charactoristic air leaks, a sticky throttle cable or throttle pedal getting caught on your mats. Basically when you take your foot off the throttle the revs should be back at tickover almost immediately. Does your throttle respond differently when the car is stationary to when it is on the move, are you just experiencing engine braking, what happens to the revs when you're on the move if you depress the clutch at the same time as you release the throttle?
that's the problem I have, I wrote a thread about it but not solved it yet 
I have checked for leaks and no engine codes stored and I find its mostly in first for some reason like the car knows what gear I'm in , though I have noticed a rattle from under the car and I'm kinda thinking that's the cats braking up and maybe clogging the exhaust and confusing the ecu? god knows but have not had chance to do anything much to it with the crappy weather
I have checked for leaks and no engine codes stored and I find its mostly in first for some reason like the car knows what gear I'm in , though I have noticed a rattle from under the car and I'm kinda thinking that's the cats braking up and maybe clogging the exhaust and confusing the ecu? god knows but have not had chance to do anything much to it with the crappy weather 
Our 2.8 has the throttle hang thing and has done as long as we have had it.the M has a much more responsive throttle .
if i am driving and am rolling to a stop, the car wont go back to idle untill i am actually stopped
i have no codes, no leaks, engine purrs like a kitten
i am thinking that it is purposeful, i dont have sticky throttle or body and nothing in the way on the floor, everything as it should be ;-)
i just took it that thats the way it is, but i would like to know why....
only thing i can think of is that if the engine holds the revs for a quick take off, like launch control... but it does seem to be tied in with the speed as in it wont drop till the car is stopped. if i stop the car quick it will hold for like 2 or three seconds then drop, if i depress the clutch in first while rolling, it wont drop again until the car stops this is why i think it is purposeful and i could be completly wrong
i have no codes, no leaks, engine purrs like a kitten
i am thinking that it is purposeful, i dont have sticky throttle or body and nothing in the way on the floor, everything as it should be ;-)
i just took it that thats the way it is, but i would like to know why....
only thing i can think of is that if the engine holds the revs for a quick take off, like launch control... but it does seem to be tied in with the speed as in it wont drop till the car is stopped. if i stop the car quick it will hold for like 2 or three seconds then drop, if i depress the clutch in first while rolling, it wont drop again until the car stops
this is why i think it is purposeful and i could be completly wrong 
Interesting David, I'll have to pay a bit more attn to my car as I haven't noticed that problem (?) ! JIMif i am driving and am rolling to a stop, the car wont go back to idle untill i am actually stopped
i have no codes, no leaks, engine purrs like a kitten
i am thinking that it is purposeful, i dont have sticky throttle or body and nothing in the way on the floor, everything as it should be ;-)
i just took it that thats the way it is, but i would like to know why....
only thing i can think of is that if the engine holds the revs for a quick take off, like launch control... but it does seem to be tied in with the speed as in it wont drop till the car is stopped. if i stop the car quick it will hold for like 2 or three seconds then drop, if i depress the clutch in first while rolling, it wont drop again until the car stops
Is it using any more fuel than normal? To hold an rpm would suggest that it maybe still fuels a split second longer than it should when the throttle is shut,almost your engine burning off excess? Have you removed the air pipe and checked that your throttle body is clean ? If there is any build up around the butterfly valve it may not be snapping shut as it should it wouldn't produce any error codes but would give the symptom as the throttle still being open more than it should be.
Have you tried blipping the throttle from the engine bay ? Same result ? You can make sure then the throttle body is shutting with your fingers.
The only other thing is possible a split hose or air leak some sort of unmetered air in the system causing a mis fuel again wouldn't necessarily give an error but would make the engine misbehave.
Most engines when bliped on the throttle normal drop quickly to approx 1000rpm then in a split second down to tickover ,holding the revs high suggests air or fuel related issue not as your finding hardware related.
Just my thoughts......
Have you tried blipping the throttle from the engine bay ? Same result ? You can make sure then the throttle body is shutting with your fingers.
The only other thing is possible a split hose or air leak some sort of unmetered air in the system causing a mis fuel again wouldn't necessarily give an error but would make the engine misbehave.
Most engines when bliped on the throttle normal drop quickly to approx 1000rpm then in a split second down to tickover ,holding the revs high suggests air or fuel related issue not as your finding hardware related.
Just my thoughts......
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Hi and thanks for your reply. fuel usage is a bit high and many of your thoughts are the same as mine but I'm begining to think I have an issue with the throttle position switches. Air leaks - none, throttle cable okay and adjusted correctly - same result on blipping throttle from pedal or at body. Body has been off more than once and cleaned as has ICV, CCV has been replaced too. I may have an issue with the ECU but can't be sure, I get no fault codes but at present have the airbag light on and still no codes showing and with my engine problems I would expect at least one code. The reason I'm leaning toward TPS faults is that the engine more often than not feels as if it's in some kind of limp mode and on cold starts the Secondary Air pump system doesn't always run though all parts are good as is vacuum. I also have a non-working exhaust flap yet that system all checks out. I know it's popular to disconect the flap but in my case I belive it is associated with my other problems. If I have a TPS fault then it seems logical that the necessary signal from TPS/revs that operates the flap will be absent and hence the flap won't work. If I have started the engine and the cold start system hasn't operated I can sometimes switch off and then restart and the cold start will then work, under these circumstances the engine performs quite differently, better MPG for a start. Having found more info on the throttle body it suggests that when in limp/fault mode the ECU switches the throttle body to a more manual mode and therefore some aspects of the fuelling process will be different. Over supply of fuel to the injectors could well be happening and this might be the slow drop of revs; the pressure dropping. I also supect that if the throttle body has issues with TPS then the motor in the body won't function to reduce revs in loss of car control situations, that's why you get limp mode, safety. So TPS could well be at fault but why no codes or EML, is that a fault in the ECU? I'm pretty sure it's not air leaks as removal of the oil filler cap or dipstick cause the engine to run lumpy, I've done a lot of checking for leaks with sprays etc and all seems good to me.
Sounds like you've covered most bases ,i undertand your thinking on the tps have you ran it with it disconnected? One to see if there is any change in behaviour and also too see if it actually gives you an error code.
If you can read and reset then nothing much to loose if disconnected makes no difference it would suggest it may be faulty a new one about £40 at a glance.
The unusual bit is no codes but then some code readers do not read your safety systems which is why the airbag light may not be flagging
Just to add limp mode normal restricts speed on most vehicles so will run normal but then not above say 30mph ?
It could lean towards ecu but i don't think so if it runs ok again fuelling is related to lambda a lot have reported issues with running and fueling when the lamdbda sensors are on the way out ,again not sure if it would error if failing ie misreading or error on a totally failed sensor only others maybe able to advise you on that one. ...
If you can read and reset then nothing much to loose if disconnected makes no difference it would suggest it may be faulty a new one about £40 at a glance.
The unusual bit is no codes but then some code readers do not read your safety systems which is why the airbag light may not be flagging
Just to add limp mode normal restricts speed on most vehicles so will run normal but then not above say 30mph ?
It could lean towards ecu but i don't think so if it runs ok again fuelling is related to lambda a lot have reported issues with running and fueling when the lamdbda sensors are on the way out ,again not sure if it would error if failing ie misreading or error on a totally failed sensor only others maybe able to advise you on that one. ...
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@Antm72 the car is running at about 34 to the gallon with mixed driving and hasnt changed in the past year since ive bought it. I have had the throttle body off and it is spotless and closes correctly and tps is cleaned also. the key to me here is as i have explained above, the idle dosent drop untill the car has come to a full stop. i can hold in the clutch and let the car roll and in that length of time, as long as the car is in motion, the revs will stay up.... this to me suggests that it is tied in with the speed sensors and as such is purposely done...
It could also be connected with steering sensors too whilst the wheels are turning, it knows you may need slightly higher revs for steering use?
Tony.
Tony.
I think for peace of mind that I would be pulling each and every air hose off for a complete visual exam as there could be tiny breaks underneath that would not be reached by spraying. Only after I was 100% certain of no air leaks would I move on. The old KISS method is cheap only taking your time and labour. It doesn't take a large break to throw the mixture off and produce these symptoms. On a Volvo I had my cold start injector was not shutting down. Fixed with a £1 piece from a Mazda after being stranded in the USA over as weekend, two nights motel, tow job, two days wages lost. JIM