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Idle Question

R

Riggernut

New member
Does anyone know why my idle is lower when cold and just over 1000 when warm. I would expected it be the other way round? Idle when cold still sound lumpy. MPG poor, black soot out of the exhaust

Recently replaced
DME Temp Sensor
DME
FPR

Cured warm starting issues.

Still have buzzing from the fuel pump area when cold dissappears after a while, thought the 2nd hand FPR would have cured this.

Leaning towards ICV or AFM

Any thoughts?
 
That's not an idle question. And idle question is something like "How many angels can dance on the head of a pin?"

Idle will be slower when cold as the oil will be thicker and hence more drag on the engine. I'd be thinking AFM rather than ICV.


Oli.
 
[;)]

Is it worth taking the AFM apart to fix the barn doors? could be that I suppose. Seen a 2nd hand one on ebay but I get the feeling it might be a false economy.
 
Barn doors don't go wrong, as far as I know. The tracks on the PCB underneath do go grotty tho', and wear out. It can be well worth taking the unit out and apart and looking to see what's going on.

Another thought; as far as I am aware, the car only has ECU-controlled idle when the throttle is at rest, and this is signalled to the ECU by the throttle position switch. It's worth checking that this is switching as it should; give the throttle cam a push with you fingers and listen to hear whether there is a faint 'click' when it returns to rest. Have a poke around the switch terminals with a multimeter as well to make sure that it is working as it should (you'll need to unplug it from the loom to do this.)


Oli.
 
Yep had a play with the TPS, I need to adjust the cable as there is a little bit of play, needs the slack taking out. The switch does click ok.
When you say ECU controlled Idle is that DME or ECU.

The car has a 'superchip' ECU fitted in 1991. I didn't even know 'superchips' had been running for that long! Maybe it just need a remap?
 
DME is just the relay that turns the fuel pump on (as I understand it), so not this. When I say "ECU" I mean (generically) an engine control unit; something electronic that controls the idle. What or where this is I don't know - sorry.

The Superchips chip in the ECU will be doing the same job now as it did in 1988, and won't be remappable. I strongly suspect your problem is a poor connection somewhere, or a failed component. If you are sure that the TPS is correctly telling the ECU when the car should be on idle then I'd be checking the connections to the ICV and possibly cleaning out the ICV as well (it gets gunged up with crud and can be helpfully cleaned out - squirt carb cleaner into it until it runs out clean, rather than brown-coloured.) And think about taking the AFM apart and cleaning the tracks and bending the wiper arm slightly.

(Gosh, who'd have thought one could use so many TLA's about something as simple as a car engine, eh?!)


Oli.
 
Having just changed my Lambda sensor and it being fresh in my memory, could that cause idle issues ?
 
Lambda could be up he spout, but this would probably show with other problems elsewhere.

Same goes for spark plugs, plug leads, rotor arm and dizzy cap. These all need to be in good nick, but all will cause problems with other things as well as idle if they are failing.


Oli.
 
Does the Turbo have a lambda? in fact there is a disconnected plug on the bulkhead could be it, the exhaust has been been replaced for a SS unit so perhaps no need for it. Strange thing was it just had an MOT and flew through emissions.

Plugs, leads, dizzy, rotor arm, coil, battery all changed in the last 2 years
 
Sounds like you have auxiliary air issues - when cold, extra fuel is injected to help starting and additional air is provided to increase idle speed a little - this is because fuel injected engines do not have a choke like a carburetor. Because you are getting soot out the exhaust it sounds like you ARE getting extra fuel but as your idle speed is low (it is actually flooding a bit) you need extra air to compensate.

I'd be checking the auxiliary air regulator (normally open when cold and closed when hot).
 
as others have already said the usual culprets are the AFM and the idle ACV
but you should also check your fuel pressure to make sure that the FPR valve is working correctly . Leaking Injector ?possibly

Also the engine temperature sensor ETS [;)] if faulty will cause erratic cold starting and idle when warm . They are cheap enough to replace but can be tested (see parragon or Clarkes garage)

Do not rule out a leak somewhere in the vacumm system as that will definitly effect starting and idle . Check all pipes and connectors thoroughly .


I wouldn't touch the TPS switch as it is unlikely to have just developed a fault its just a simple microswitch and easily tested with multimeter.

I would strongly recommend that you do not adjust the idle , its unlikely to have adjusted itself and any adjustment that you make will mask the true source of the problem
 
Also the engine temperature sensor ETS if faulty will cause erratic cold starting and idle when warm . They are cheap enough to replace but can be tested (see parragon or Clarkes garage)

Do not rule out a leak somewhere in the vacumm system as that will definitly effect starting and idle . Check all pipes and connectors thoroughly .

I wouldn't touch the TPS switch as it is unlikely to have just developed a fault its just a simple microswitch and easily tested with multimeter.
Click to expand...

Agree entirely
 
Well I went for spraying carb cleaner into the ICV/AAV. I'll know on the next cold start tomorrow whether that's done the trick.
 
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