Idle at 2000rpm

[johnyrover]

Hi guys. Got a tricky one. Since I live 1.5hrs from the nearest wallet drainer, I thought I'd run it past you. The beast has been running like a dream for the last 20,000k's, but I started it up the other week and it went to 1200rpm on startup at idle. Over the next week or so it went up to 2000rpm. This was the only symptom that something was wrong. I have searched high and low for an answer and they all seem to correspond with other symptoms that my car does not have. So far I have ascertained that the stepper motor is clean, closes on shutdown then pulls back a bit. I have adjusted it manually to where it does not over rev and disconnected it. I have cleaned the throttle body and the MAF. There are no air leaks. The whole rig is running really smooth with good economy 13.5l to the 100k at standard height (on coils). There was a mild surging at idle which has all but subsided after cleaning the throttle body. I think if anything the IAC could have been pulling back a bit far, because It is practically at the closed position now. Idle is now at 700 cold up to 900 hot.
A Nanocom Evo is on the Christmas shopping list. The hotty is a bit tired of the obsession.:D
Any thoughts would be cool.
Thanks guys.

[mick88]

I may be way off the track but i had a Daihatsu diesel do that once and it had a leather diaphragm on the fuel pump that had perished.


Cheers, Mick.

[PhilipA]

Usually on a 14 CUX the IAC OPENS fully on shutdown. Thsi is to ensur eit gets exercised and doesn't become sticky . Ha ha .
That is why you get high revving for a while when it gets sticky.
I think that GEMS would be similar.
I assume GEMS as you don't state which model.
On Thor the IAC is much more powerful and a different system of a sleeve valve.
Look a petrol engine MUST have an air leak if it is idleing fast as the throttle blade "throttles " the air into the engine. Have you checke dthat the throttle blade and area is clean? The only other reason could be excessive advance., or maybe long shot FPR staying rich on GEMS only( maybe not even GEMS).
Regards Philip A

[johnyrover]

Thanks Mick. I'll check it out. I was hoping no-one would say the f word.:)
Cheers

[Keithy P38]

You have probably already checked, but I am going to state the obvious anyway!

Have you checked all vacuum lines and any of those additional ports on the intake manifold? Even a quick check of the torque of your manifold bolts might bring up something!

Do the gems v8's run vacuum booster for the brakes? I suppose they would/should be the same as a Thor.

Cheers
Keithy

[johnyrover]

Sorry bout that. What is FPR? Both myself and the local mech had a good spray, and checked the vacuum lines. Pretty sure not a leak. I also gave the butterfly area a good clean as there was a definite build up in the form of a black ring. That evened out the idle a bit but also raised the idle a tiny bit.
Cheers.

[johnyrover]

Yep checked vacuum hoses and sprayed like a tomcat. The intake manifold/valley gasket was changed not long before this started, so I hope they know what they were doing. I did not consider them overly conciencious but they seemed capable. I have not seen anything that looks like a vacuum booster for the brakes, rather I think the accumulator does the same job as well as maintains pressure for the ABS.
Cheers

[Hoges]

FWIW: surging can be a symptom of a failing throttle positioning sensor (TPS). Presume you have checked the clearance of the throttle cable/cruise control cams as well?

[PhilipA]

Sorry bout that. What is FPR?

Fuel Pressure Regulator
Regards Philip A

[johnyrover]

TPS did come up in my research, found a manual test to assess the voltages. (Looking forward to the Xmas pressy Nanocom !) I'll know soon enough if it is the TPS as this starts messing with the gearbox in a big way apparently. If by cams you mean the slack in the cables from the accelerator and the cruise control, then yep, they have just a tiny bit of slack in both and are seated. Also the butterfly is closing perpendicular with no gap. Phillip A I'll start researching FPR.
Thanks guys

[johnyrover]

Went to my local Auto elec. His tool would'nt pick up my BeCM, but found my stepper motor sitting at 71 steps with a hot motor running. I think this should be 20 to 30. So I am hoping that an electronic reset will stop the high idle. His tool would not set it. Come on Nanocom!!!!:)
Will let you know how it goes.
BTW Just did over a thousand K's of my trip up the coast and apart from the high idle the whole rig is running like a dream. And I think it likes 95ron juice. They only had 91ethenol blend so I went 95 and got instant improved economy. Down a litre per hundred K's at 110kph, and up and down some pretty big hills.
Roll on!

[justinc]

resetting all adaptive values should do the trick.

jc

[Scouse]

resetting all adaptive values should do the trick.

jcYep, it fixed my 2000rpm idle after I changed the BECM/engine ECU/inst pack set.

[Hoges]

Yep, it fixed my 2000rpm idle after I changed the BECM/engine ECU/inst pack set.

umm .. what's an "inst pack set"? :eek: please:angel:

[glenhendry]

Make sure your throttle cable isnt kinked or wrapped around something. Mine is sensitive to mispositioning. Also, make sure that the butterfly in the throttle moves freely with the cables unattached.

Also, the fuel pressure is easy to test (on THOR) with a dispopsable $3 tyre air pressure tester (palm sized), it has the correct "chuck" (female schraider value) fitting off the shelf. It will at least let you know if your fuel pressure is in the ballpark. Mine read ~50psi which seemed to be pretty close to the mark.

[Scouse]

umm .. what's an "inst pack set"? :eek: please:angel:I bought a car with a suspected BECM fault so I swapped the BECM, engine ECU & instrument pack out of another car to fit to the new one.
Changing all 3 components together solves the problem of BECM / engine ECU communication mis-match & also keeps the BECM / instrument pack km in sync.

[johnyrover]

Up to 3000k's on our coast trip. Still no dramas from having the IACV unplugged. Just got to watch putting it in reverse at 1000rpm. Still getting great economy and running smooth. Really looking forward to not having to take my car to people who are "willing to have a go, but can't promise anything". I know they mean well, but.....
Good news is we are moving to Tweed soon and it looks like the Rangey mechs are not so thin on the ground.
Anyhoo :D