280 - high revs when warm
Discussion
Sorry it's taken so long to get back to this, finally got back to it yesterday. Thanks for the suggestions, I've worked through them.
Engine still idles at 14/1500 rpm when warm.
I've checked for air leaks, none found. If I squeeze the hose from the AAD to the throttle body to reduce airflow, the revs come down to normal. That shouldn't happen if the engine is warm.
I couldn't get any voltage reading from the plug contacts but I switched it with the power supply for the engine temp sender unit and temp gauge still shows a reading so I think I have power to those plugs.
Then I took the AAD off the engine and stood it in some hot water. The bimetal strip works and the aperture closes, however, it won't close on the car. Took the car for a drive, then idled it for 10 minutes. Revs didn't budge from 1500. Turned off the car and removed the AAD hoses and looked through it, still fully open.
Wondering if the heating coil in the AAD could be faulty. Might it need the coil and engine heat to close? Do we know at what temp it closes?
Engine still idles at 14/1500 rpm when warm.
I've checked for air leaks, none found. If I squeeze the hose from the AAD to the throttle body to reduce airflow, the revs come down to normal. That shouldn't happen if the engine is warm.
I couldn't get any voltage reading from the plug contacts but I switched it with the power supply for the engine temp sender unit and temp gauge still shows a reading so I think I have power to those plugs.
Then I took the AAD off the engine and stood it in some hot water. The bimetal strip works and the aperture closes, however, it won't close on the car. Took the car for a drive, then idled it for 10 minutes. Revs didn't budge from 1500. Turned off the car and removed the AAD hoses and looked through it, still fully open.
Wondering if the heating coil in the AAD could be faulty. Might it need the coil and engine heat to close? Do we know at what temp it closes?
Hi, looking at RCK974X's excellent guide as to how CIS works, I see that he says of the AAD " It's mostly electrically heated, but some are bolted to block
(Wedge one isn't really warmed by engine much)."
If you suspect the heating element has failed, perhaps you could check this by putting a 12v feed to the AAD and see if this causes the shutter to close?
Ian
(Wedge one isn't really warmed by engine much)."
If you suspect the heating element has failed, perhaps you could check this by putting a 12v feed to the AAD and see if this causes the shutter to close?
Ian
madformotors said:
mrzigazaga said:
I might have one in my box of 280i bits....Ill have a look and get back to you...If I can I will have a looksie today...
And if there should be some red wheel nuts in there....
Ian
...I still cant find them....I have a feeling I may of put them in the BBWF raffle...However if I do find them....they are yours..
...Well I had a look and couldn't find the spare AAD....Or the nuts...(Doh)...Its driving me bonkers not knowing what happened to them...
440Interceptor said:
Yep thanks, sounds like a plan. Will find local auto electrician and get them to test it. Looks like finding a new one could be interesting..
Hi, if it turns out that the AAD is u/s you could try www.caprigear.co.uk for a used one - they were very helpful when I was after a WUR - another once common but now hard to find part. IanHave just seen the latest responses ....
If valve is not closing then it almost certainly means the unit is not being heated. Either the unit has no power, or the heating element is faulty.
If you have a test meter, the plug should have 12 volts supplied to it when engine is running. Use a couple of small nails or wire or something to insert into connectors.
BUT - if it's a dodgy earth or something - an ordinary 12v sidelight bulb may be a better test. Make sure it lights up properly.
You should also be able to see that the unit itself has a measurable resistance across its terminals - after all it's simply a heater....not anything fancy.
The connectors can get quite grungy with all the temperature cycling...
for info -
That warm up unit doesn't do anything to the fuel injection at all, it's just a 'cold engine speed up' by letting more air in.
Hell, the engine might even idle OK when stone cold, and you can then block the pipes off !
If valve is not closing then it almost certainly means the unit is not being heated. Either the unit has no power, or the heating element is faulty.
If you have a test meter, the plug should have 12 volts supplied to it when engine is running. Use a couple of small nails or wire or something to insert into connectors.
BUT - if it's a dodgy earth or something - an ordinary 12v sidelight bulb may be a better test. Make sure it lights up properly.
You should also be able to see that the unit itself has a measurable resistance across its terminals - after all it's simply a heater....not anything fancy.
The connectors can get quite grungy with all the temperature cycling...
for info -
That warm up unit doesn't do anything to the fuel injection at all, it's just a 'cold engine speed up' by letting more air in.
Hell, the engine might even idle OK when stone cold, and you can then block the pipes off !
Thanks Andy. I took the unit to the auto electrician who set it up with a 12 volt feed and it closed just fine, thanks goodness, they're not cheap.
So it must be the supply. i checked that earlier on and got nothing at the plug but I'll d it again to be sure, There supposed to be a safety switch that needs bypassing but I can't see it where it's supposed to be. Shouldn't matter if the engine's running though I think.
I think that circuit also has the warm up regulator on it. There is a fuse but it fuses the fuel pump too and that's fine so it can't be that.
I pulled the plugs out yesterday and they were filthy dirty with soot. Theory: if there's no power to the WUR or the AAD, then the engine will run rich even when warm and.. soot. Sound reasonable?
So it must be the supply. i checked that earlier on and got nothing at the plug but I'll d it again to be sure, There supposed to be a safety switch that needs bypassing but I can't see it where it's supposed to be. Shouldn't matter if the engine's running though I think.
I think that circuit also has the warm up regulator on it. There is a fuse but it fuses the fuel pump too and that's fine so it can't be that.
I pulled the plugs out yesterday and they were filthy dirty with soot. Theory: if there's no power to the WUR or the AAD, then the engine will run rich even when warm and.. soot. Sound reasonable?
There is a thermal switch at the front (the one which looks like an oversized temp sender) but this is only the control for the start up injector (on the side of the plenum box), so that this injector does not inject when engine is warm/hot.
have a look at a wiring schematic of 'K' injection (there's several on the web), as I remember, there is no switch in the air device circuit - it just goes straight to ignition feed, so it should have 12 volts supplied to it whenever key is 'on'. As I remember there is a join in the loom on that side - 12 volts (ignition feed) goes to the thermal switch at the front of engine and to the air device, so could be the join has got corroded ??
Or wire could be broken somewhere, or if it's been rewired, it's possible it's been done wrong.
And don't forget to check the earth return wire(s) too.....that can also be dodgy
have a look at a wiring schematic of 'K' injection (there's several on the web), as I remember, there is no switch in the air device circuit - it just goes straight to ignition feed, so it should have 12 volts supplied to it whenever key is 'on'. As I remember there is a join in the loom on that side - 12 volts (ignition feed) goes to the thermal switch at the front of engine and to the air device, so could be the join has got corroded ??
Or wire could be broken somewhere, or if it's been rewired, it's possible it's been done wrong.
And don't forget to check the earth return wire(s) too.....that can also be dodgy
Success!
I traced the wiring and found the warm up regulator and the AAD were using the same earth which went into a new looking 10 pin plug but..there was no earth wire coming out the other side of the plug... Then I found an unused earth wire with a spade socket sliced into an existing earth..put em together and bingo car now idles at 1000rpm give or take when at normal operating temp.
Must have been done when I had the auto electrician get the car ready for licensing. I've had the car since early 2000s and I definitely didn't do it. Wouldn't have known how! I'll get it tidied up properly when I next see them.
I don't think it's running rich now either, will put the meter on the WUR plug and check spark plugs after a few more kms.
Thanks for your help gents.
I have a list of other things that need done before it goes on the market... Shame after all the work I've put into it but I bought its very big brother (still a wedge of course) and I'm only allowed one! First and most important is a gearbox rebuild, but I'll start another thread for that so others doing similar work can look it up later if they wish. .
I traced the wiring and found the warm up regulator and the AAD were using the same earth which went into a new looking 10 pin plug but..there was no earth wire coming out the other side of the plug... Then I found an unused earth wire with a spade socket sliced into an existing earth..put em together and bingo car now idles at 1000rpm give or take when at normal operating temp.
Must have been done when I had the auto electrician get the car ready for licensing. I've had the car since early 2000s and I definitely didn't do it. Wouldn't have known how! I'll get it tidied up properly when I next see them.
I don't think it's running rich now either, will put the meter on the WUR plug and check spark plugs after a few more kms.
Thanks for your help gents.
I have a list of other things that need done before it goes on the market... Shame after all the work I've put into it but I bought its very big brother (still a wedge of course) and I'm only allowed one! First and most important is a gearbox rebuild, but I'll start another thread for that so others doing similar work can look it up later if they wish. .
....
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