Tickover too fast - 2.8 FHC - help needed
Discussion
I agree it will be the Auxilary air device stuck open which is looking from the front of the car at the front left of the Plenum and bleeds air from before the throttle to the left hand side of the plenum next to the cold start injector. To check start car running and squeeze the rubber tube. The revs should drop Then just needs a clean or a 15mm plumbing end cap jubilee clipped in the hose to block it off. That's what mine has had for 2 years and starts ok. Doesn't run well when really cold but will work till the Aux valve is cleaned.
FlipFlopGriff said:
jeff m said:
Almost always the Aux air device stuck open.
Pull off the hoses if you can see thru it when HOT take it off and give it some carb cleaner.
Is this the red thing stuck on the front centre of the plenum with hoses off either end?Pull off the hoses if you can see thru it when HOT take it off and give it some carb cleaner.
FFG
Two hoses....that'll be it.
It only a few minutes to take it off and clean it really well.
Give it a good soaking, blow it out then hold it over a gas ring to warm it up, you should see the innerds start to move across the hole and shut it off.
When it cools it should open up again. Car will appreciate this working properly as it gives extra air to coincide with cold start injecter. (op'd by thermotime thingy)
Right,
Auxiliary air device cleaned up and working proiperly. Have a spare in box of bit I bought off e-bay and no improvement on the original. There are 2 wires coming off the device, a brown and a black with red trace. This seems to be common on the sensors. It gets up to temp but doen't seem to send the signal back to reduce the revs. When the pipe is squeezed (one going into the plenum) the revs do drop.
Assume brown is earth so what does the black/red do and where does each sensor connect to. Can't get the revs below 1,700 so no way going to pass an MoT.
I've cancelled the MoT so not going to be at BBWF - very disappointed!!!!!!!!!!!
FFG
Auxiliary air device cleaned up and working proiperly. Have a spare in box of bit I bought off e-bay and no improvement on the original. There are 2 wires coming off the device, a brown and a black with red trace. This seems to be common on the sensors. It gets up to temp but doen't seem to send the signal back to reduce the revs. When the pipe is squeezed (one going into the plenum) the revs do drop.
Assume brown is earth so what does the black/red do and where does each sensor connect to. Can't get the revs below 1,700 so no way going to pass an MoT.
I've cancelled the MoT so not going to be at BBWF - very disappointed!!!!!!!!!!!
FFG
Hi,
I had the exact same problem on my 280i a few years ago, well quite a few now, turned out to be electrical, if you start the car put a multimeter across the electrical connector that connects to the Auxillary Air device you should see a voltage, sorry can't remember what value exactly but you should be getting something, I was getting nothing, traced wiring all the way back to a dodgy connector on the passenger side underneath the air box, there was a whole bunch of wiring under there and alot of the connectors were looking a bit worse for wear, If I was you trace the wires back as best you can, replace every connector you can find if it looks even remotely like it might be related, or use the multimeter as you go see if you can isolate the point of failure, I had to remove the air box and do alot of the tracing from underneath the car as you simply can't see much of it from the top. Hope this hepls, sorry can't be any more specific, it was a while ago.
Cheers,
Rich.
I had the exact same problem on my 280i a few years ago, well quite a few now, turned out to be electrical, if you start the car put a multimeter across the electrical connector that connects to the Auxillary Air device you should see a voltage, sorry can't remember what value exactly but you should be getting something, I was getting nothing, traced wiring all the way back to a dodgy connector on the passenger side underneath the air box, there was a whole bunch of wiring under there and alot of the connectors were looking a bit worse for wear, If I was you trace the wires back as best you can, replace every connector you can find if it looks even remotely like it might be related, or use the multimeter as you go see if you can isolate the point of failure, I had to remove the air box and do alot of the tracing from underneath the car as you simply can't see much of it from the top. Hope this hepls, sorry can't be any more specific, it was a while ago.
Cheers,
Rich.
Richybaby said:
Hi,
I had the exact same problem on my 280i a few years ago, well quite a few now, turned out to be electrical, if you start the car put a multimeter across the electrical connector that connects to the Auxillary Air device you should see a voltage, sorry can't remember what value exactly but you should be getting something, I was getting nothing, traced wiring all the way back to a dodgy connector on the passenger side underneath the air box, there was a whole bunch of wiring under there and alot of the connectors were looking a bit worse for wear, If I was you trace the wires back as best you can, replace every connector you can find if it looks even remotely like it might be related, or use the multimeter as you go see if you can isolate the point of failure, I had to remove the air box and do alot of the tracing from underneath the car as you simply can't see much of it from the top. Hope this hepls, sorry can't be any more specific, it was a while ago.
Cheers,
Rich.
Rich,I had the exact same problem on my 280i a few years ago, well quite a few now, turned out to be electrical, if you start the car put a multimeter across the electrical connector that connects to the Auxillary Air device you should see a voltage, sorry can't remember what value exactly but you should be getting something, I was getting nothing, traced wiring all the way back to a dodgy connector on the passenger side underneath the air box, there was a whole bunch of wiring under there and alot of the connectors were looking a bit worse for wear, If I was you trace the wires back as best you can, replace every connector you can find if it looks even remotely like it might be related, or use the multimeter as you go see if you can isolate the point of failure, I had to remove the air box and do alot of the tracing from underneath the car as you simply can't see much of it from the top. Hope this hepls, sorry can't be any more specific, it was a while ago.
Cheers,
Rich.
The black and red wire that comes out by the air box - what should it be connected to? Tried everything but can't cure the problem? There are 4 or 5 connectors which we seem to have resolved other than this one last issue.
FFG
FlipFlopGriff said:
Right,
Auxiliary air device cleaned up and working proiperly. Have a spare in box of bit I bought off e-bay and no improvement on the original. There are 2 wires coming off the device, a brown and a black with red trace. This seems to be common on the sensors. It gets up to temp but doen't seem to send the signal back to reduce the revs. When the pipe is squeezed (one going into the plenum) the revs do drop.
Assume brown is earth so what does the black/red do and where does each sensor connect to. Can't get the revs below 1,700 so no way going to pass an MoT.
I've cancelled the MoT so not going to be at BBWF - very disappointed!!!!!!!!!!!
FFG
Dont get much chance to get online but thought this may help. From what I gather, its not a sensor as such, just an air switch.Auxiliary air device cleaned up and working proiperly. Have a spare in box of bit I bought off e-bay and no improvement on the original. There are 2 wires coming off the device, a brown and a black with red trace. This seems to be common on the sensors. It gets up to temp but doen't seem to send the signal back to reduce the revs. When the pipe is squeezed (one going into the plenum) the revs do drop.
Assume brown is earth so what does the black/red do and where does each sensor connect to. Can't get the revs below 1,700 so no way going to pass an MoT.
I've cancelled the MoT so not going to be at BBWF - very disappointed!!!!!!!!!!!
FFG
Theres an article about the MFI on this site.
http://www.graemef.rapidial.co.uk/
Hope it helps
Kev
Sorry I'm slow in checking this thread.
The two wires in the AAD do not do anything externally.
They power a bimetal strip which heats up and closes it. (although it will/should close from physical heat.)
If you closed the pipe off and the revs dropped then that is the source of your unwanted or "extra" air confirmed.
I have a US 280 '85 so wiring may be slightly different but power should come from fuse 1 via the engine run sensor and be hot when car is running. Possibly a Blue/Red. The other is a ground.
To test you could pick up the 12 volts from the WUR and see if that shuts it off.
Edit
Just re read your post. You should be getting 12v on that Black/red with engine running, ie fuel pump operating (same feed) coming from engine run sensor and ultimately fuse 1 (which does the feul pump too, so that's ok)
Should you not have 12volts on your WUR then it really must be the Engine run sensor (yellow wire on mine)
The two wires in the AAD do not do anything externally.
They power a bimetal strip which heats up and closes it. (although it will/should close from physical heat.)
If you closed the pipe off and the revs dropped then that is the source of your unwanted or "extra" air confirmed.
I have a US 280 '85 so wiring may be slightly different but power should come from fuse 1 via the engine run sensor and be hot when car is running. Possibly a Blue/Red. The other is a ground.
To test you could pick up the 12 volts from the WUR and see if that shuts it off.
Edit
Just re read your post. You should be getting 12v on that Black/red with engine running, ie fuel pump operating (same feed) coming from engine run sensor and ultimately fuse 1 (which does the feul pump too, so that's ok)
Should you not have 12volts on your WUR then it really must be the Engine run sensor (yellow wire on mine)
Edited by jeff m on Friday 18th July 04:35
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