So, my old 2.8 is down at my parents where its been sat for 10 months or so.
I'm bringing it back to Jersey soon, but its developed a problem..
Engine starts, ticks over ok, gentle pressure on acceleration will raise revs to around 2,200rpm but after that it bogs down and dies..
My dad and a friend down there have been trying to get it fixed but not having much joy.. He's sending me pictures of what he's got to so far, but after talking to a few people they've suggested cleaning the ICV.. They tried to follow this guide - http://www.zroadster.net/forum/viewtopic.php?t=8142 - but apparently the engine bay looks different to the pics..
Does anyone have any ideas/suggestions? I'll post pictures up once I've received them..
Thanks!
Help... Idle problem
Help... Idle problem
ex.. BMW /// M Coupe 00, Estoril, ACS Front flippers, KWV3.. 
Re: Help... Idle problem
Ok, so it appears that the throttle is shut hard - should it be possible to push open?
ex.. BMW /// M Coupe 00, Estoril, ACS Front flippers, KWV3..
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Southernboy
- Joined: Thu 07 Oct, 2010 12:39
- Posts: 6437
- Location: Johannesburg
Re: Help... Idle problem
It should move when the accel pedal is pressed if it's a bowden cable system (that's the "old fashioned way they used to work - the newer Z3's came with a motor driven throttle which was activated by sensors in the accel pedal and controlled by the DME) So, if you have the older cable system, then it should move. If it's the newer system, you may have a problem with a variety of items from the pedal sensors to the motor which actuates the throttle to the DME to simple connections between these items. Looking at the pic you have shown, it seems you have the newer motor driven throttle - that will be the black box thingy attached to the side of the throttle if it's not the TPS. (Throttle Position Sensor) I would say that the probability is the motor is siezed up due to the car standing for so long. Perhaps strip the throttle out and give everything a thorough lean up and spray liberally with WD40 or such.
At the pedal end, there is a thing called a potentiometer. It basically works like the dimmer on a light switch. The more you turn the knob the greater the current and the brighter the light etc etc. That potentiometer has two Hall sensors (they both do the same job - the DME just uses one to check the other so that it cancels out any stupid errors in the messages received at the DME).
It is not common for the potentiometer to malfunction, I've never heard of it ever happening. So back to the throttle area which is more likely to be the problem since it is exposed to the atmosphere and oxidation / rust etc may have siezed up the little motor that actuates the throttle butterfly you can see in your pic. There is also a TPS there which sends signals to the DME to confirm the request of the pedal Hall sensors that it is behaving as requested and opening / closing as required. Since the throttle isn't moving at all, the sensor can't do much.
Definitely sounds as if it's a mechanical problem, and for an hour or two of effort removing / cleaning and replacing the throttle, it's worth doing before you start spending money on sensors etc etc. It'll also allow you the opportunity to remove and inspect the rubber boots / connections to the throttle for cracks and air leaks which will also have an effect on the smooth running of the motor.
If it's the older cable actuated system, then it's very likely the butterfly shaft has seized, in which event, you need to get the throttle out and soak it in a cleaning fluid which may release the shaft and if you're fortunate, then you can lube it well with WD40 once cleaned up.
At the pedal end, there is a thing called a potentiometer. It basically works like the dimmer on a light switch. The more you turn the knob the greater the current and the brighter the light etc etc. That potentiometer has two Hall sensors (they both do the same job - the DME just uses one to check the other so that it cancels out any stupid errors in the messages received at the DME).
It is not common for the potentiometer to malfunction, I've never heard of it ever happening. So back to the throttle area which is more likely to be the problem since it is exposed to the atmosphere and oxidation / rust etc may have siezed up the little motor that actuates the throttle butterfly you can see in your pic. There is also a TPS there which sends signals to the DME to confirm the request of the pedal Hall sensors that it is behaving as requested and opening / closing as required. Since the throttle isn't moving at all, the sensor can't do much.
Definitely sounds as if it's a mechanical problem, and for an hour or two of effort removing / cleaning and replacing the throttle, it's worth doing before you start spending money on sensors etc etc. It'll also allow you the opportunity to remove and inspect the rubber boots / connections to the throttle for cracks and air leaks which will also have an effect on the smooth running of the motor.
If it's the older cable actuated system, then it's very likely the butterfly shaft has seized, in which event, you need to get the throttle out and soak it in a cleaning fluid which may release the shaft and if you're fortunate, then you can lube it well with WD40 once cleaned up.
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therealdb1
- Joined: Tue 25 Jun, 2013 21:47
- Posts: 263
Re: Help... Idle problem
You say it is an "old" 2.8 so I'm guessing that it has a cable and it is one of those hybrid throttle bodies where the motor overrides the cable for traction control.
I read somewhere that you should not try and move the butterfly on these by hand otherwise the unit can be damaged but since it revs to 2200 rpm in response to the throttle pedal the butterfly is not likely to be stuck shut.
My best guess is that you have an air leak in the bellows and/or a duff MAF both of which can occur when a car is laid up for 10 months. Ask me how I know that!
Having said that it could be a multitude of problems and will be very difficult to diagnose without seeing the car.
First suggestion is check all of the rubber hoses between the air filter and throttle for splits then as always get the codes read. They will not tell you what the fault is but may give you an idea of areas to start looking.
Post any fault codes on here and we can have another stab at diagnosis.
I read somewhere that you should not try and move the butterfly on these by hand otherwise the unit can be damaged but since it revs to 2200 rpm in response to the throttle pedal the butterfly is not likely to be stuck shut.
My best guess is that you have an air leak in the bellows and/or a duff MAF both of which can occur when a car is laid up for 10 months. Ask me how I know that!
Having said that it could be a multitude of problems and will be very difficult to diagnose without seeing the car.
First suggestion is check all of the rubber hoses between the air filter and throttle for splits then as always get the codes read. They will not tell you what the fault is but may give you an idea of areas to start looking.
Post any fault codes on here and we can have another stab at diagnosis.
