Low idling on 400se
Discussion
Hi chaps, numpty question probably but my 1990 400SE has a slow running idle - tick over too low.
Is there anything I can adjust to raise the tick over slightly - in the good old carb days on classics one could simply turn a screw on the feed but I guess with injection this is not possible. No fuel supply problems of any other kind noted.
The Tivosi concensus would be much appreciated - kind regards all.
Is there anything I can adjust to raise the tick over slightly - in the good old carb days on classics one could simply turn a screw on the feed but I guess with injection this is not possible. No fuel supply problems of any other kind noted.
The Tivosi concensus would be much appreciated - kind regards all.
Is it a flapper system or hot wire ?
I know on a flapper like mine you can fiddle with a few bits, like throttle stop, (allen bolt under plenum where throttle plate rest on), adjust co mixture allen bolt (on top of plenum may be sealed with gunk), but better to do with a co meter attached.
Have you checked you have the right clearance when throttle is closed between the throttle butterfly and inlet ?
Made sure the throttle cable is not too slack ?
I'm sure some one will be along with the actual measurements and web site locations as I don't have them to hand
If it's a hot wire then maybe something simple
like taking the stepper motor of and cleaning it with something like petrol ? as these are no to seize a little.
Cheers
I know on a flapper like mine you can fiddle with a few bits, like throttle stop, (allen bolt under plenum where throttle plate rest on), adjust co mixture allen bolt (on top of plenum may be sealed with gunk), but better to do with a co meter attached.
Have you checked you have the right clearance when throttle is closed between the throttle butterfly and inlet ?
Made sure the throttle cable is not too slack ?
I'm sure some one will be along with the actual measurements and web site locations as I don't have them to hand
If it's a hot wire then maybe something simple
like taking the stepper motor of and cleaning it with something like petrol ? as these are no to seize a little. Cheers
I reckon its going to be a hotwire system due to being a 1990 model, but could be wrong.
If it is though, then I agree that the stepper motor is the first thing to check. Its the little black cylinder shaped thing that goes into the back of the plenum chamber. I think you just disconnect the wires, unscrew it with a big spanner and give it a good clean. try this first.
If thats not the cause, then make sure you have no air leaks around the intake system. Spraying the joints and connectors with WD40 with the engine running will show up any "holes, normally by it being sucking into the engine. It doesn't take long to reseal the plenum if in doubt, and also check things like the brake master cyliner hose for airleaks. Don't forget all the other hoses that lead to the plenum, and even the rubber seal from the oil filler cap can make a difference.
Check the throttle butterfly is set up correctly too, and hits its end stop when at idle. There should be a little grub screw on the outside of the plenum near where the throttle cable joins, and this stops the butterfly closing too much. From memory, you should be able to get something like a 0.1mm feeler gauge between the top of the butterfly and its housing.
Failing that, it could just be a mixture problem and perhaps an exhaust gas meter is needed to get things running properly!
If you car is a flapper type, then ignore most of the above!!!
Dan.
If it is though, then I agree that the stepper motor is the first thing to check. Its the little black cylinder shaped thing that goes into the back of the plenum chamber. I think you just disconnect the wires, unscrew it with a big spanner and give it a good clean. try this first.
If thats not the cause, then make sure you have no air leaks around the intake system. Spraying the joints and connectors with WD40 with the engine running will show up any "holes, normally by it being sucking into the engine. It doesn't take long to reseal the plenum if in doubt, and also check things like the brake master cyliner hose for airleaks. Don't forget all the other hoses that lead to the plenum, and even the rubber seal from the oil filler cap can make a difference.
Check the throttle butterfly is set up correctly too, and hits its end stop when at idle. There should be a little grub screw on the outside of the plenum near where the throttle cable joins, and this stops the butterfly closing too much. From memory, you should be able to get something like a 0.1mm feeler gauge between the top of the butterfly and its housing.
Failing that, it could just be a mixture problem and perhaps an exhaust gas meter is needed to get things running properly!
If you car is a flapper type, then ignore most of the above!!!
Dan.
If its Hotwire the first thing to do is set the base idle speed, the stepper motor only works on a range and cannot correct idle speed if the base idle is miles out.
Warm the car up. Clamp off the pipe leading to the stepper motor and adjust the idle speed with the grub screew to about 500 rpm the engine should just about manage to tickover at 500. Turn the ign off and release the clamp from the pipe, reset the ECU by disconecting the multi plug for 30 seconds, plug the ECU back in and Bobs your mothers brother. If this does not cure it you need to start looking at other things, air leaks, clean the stepper motor etc but at least you know the base idle is correct.
Warm the car up. Clamp off the pipe leading to the stepper motor and adjust the idle speed with the grub screew to about 500 rpm the engine should just about manage to tickover at 500. Turn the ign off and release the clamp from the pipe, reset the ECU by disconecting the multi plug for 30 seconds, plug the ECU back in and Bobs your mothers brother. If this does not cure it you need to start looking at other things, air leaks, clean the stepper motor etc but at least you know the base idle is correct.
Edited by badredwedge on Monday 5th March 07:47
...... Photo ??
1989, Think it must be an old slapper, sorry Flapper. Got no dig camera so cant send. The protrusion, marked 'Lucas' with 18 89 engraved into it, has a rubber tube emerging, which splits off under the plenum and into another section.
BUT have just taken to exhaust centre and there is a hole at lower end of right manifold, near middle section, which cant be repaired by them (ATS) - so either I need to get to a specialist for cutting and partial replacement or get a manifold £168 & vat from David Gerald, but guy there says it is best to get partial replacement as he reckons they're a bugger to match up.
BUT have just taken to exhaust centre and there is a hole at lower end of right manifold, near middle section, which cant be repaired by them (ATS) - so either I need to get to a specialist for cutting and partial replacement or get a manifold £168 & vat from David Gerald, but guy there says it is best to get partial replacement as he reckons they're a bugger to match up.
Edited by shadowfax on Saturday 31st March 08:34
shadowfax said:
Mine idles at 1000 on start up but after warming up and a run rises to 1400rpm. Nout tight on cable so what's next?
I have a similar problem if anyone can give any suggestions. Once warm idle stays at around 1500rpm and will then only drop down to 1000rpm after about 20 to 30 seconds at idle.
There is an air temperature sensor in the airflow meter. Perhaps this can cause high idle running. Don't know how you can test it, as it cannot be removed from the AFM.
Seems that more people have issues when one of the previous owners has 'played' with the AFM.
The extra airvalve, if not closing fully, provides extra air and could cause the high revs as well. Cleaning often cures this.
I have the opposite on my flapper: what ever I do (CO is ok, idle adjustment changes have no effect but lowering idle....) it is about 700 when warm, but would like to increase that a bit (like 850-900) to be sure of good oil pressure during hot idling.
Rob
Seems that more people have issues when one of the previous owners has 'played' with the AFM.
The extra airvalve, if not closing fully, provides extra air and could cause the high revs as well. Cleaning often cures this.
I have the opposite on my flapper: what ever I do (CO is ok, idle adjustment changes have no effect but lowering idle....) it is about 700 when warm, but would like to increase that a bit (like 850-900) to be sure of good oil pressure during hot idling.
Rob
350zwelgje said:
There is an air temperature sensor in the airflow meter. Perhaps this can cause high idle running. Don't know how you can test it,
The extra airvalve, if not closing fully, provides extra air and could cause the high revs
what ever I do (CO is ok, idle adjustment changes have no effect but lowering idle....) it is about 700 when warm, but would like to increase that a bit (like 850-900)Rob
The extra airvalve, if not closing fully, provides extra air and could cause the high revs
what ever I do (CO is ok, idle adjustment changes have no effect but lowering idle....) it is about 700 when warm, but would like to increase that a bit (like 850-900)Rob
Air Temp Sensor,
With ignition off, ECU disconnected and at 20 deg C, resistance between pins 6 and 27 on AFM will be approx 2500 ohms.
EAV,
With engine running and hot, only the COMBINED effect of EAV heater and engine temperature closes the valve above 60/70 deg C.
Idle speed,,
If adjust screw makes little difference to idle speed then idle gallery may be blocked (or partially so).
danny hoffman said:
Rob, try removing the idel adjustment screw completely - it might be covered in crud. Mine was and once I cleaned it I could adjust my idle speed again
Thanks for the tip (something like this was mentioned before as well), will have a look coming week (like other stuff on the to do list as in two week MOT is coming up). Had a good hoon today, and no issues only fun, fun and a lot of petrol burned....
Rob
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