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OldOne
18-11-2008, 06:33 PM
Hello all.

I hopped into the TF this morning, it started fine but just won't idle. Stalls immediately
if I lift the throttle. It does not even try to hold any idle speed.

It's a 3 litre manual. I put a new battery in it three weeks ago.

Ever since I got the car it idles between 1000 and 1200 rpm, depending on engine temp.
A bit high.

Two weeks ago I took the inlet manifold off, to check the rear plugs, and clean
the TB and inlet manifold.

Straight away when I drove the car the engine was cutting out at more than about a fifth throttle. Not an engine miss, more like an on/off switch. Drove back home on a very light throttle....parked it...in neutral, the engine wouldn't rev above 2600 rpm. When reaching 2600 rpm it would suddenly drop back to 2400 rpm as if a switch had been thrown, then it would go up to 2600 rpm and repeat the procedure every half second or so.

I cleaned the MAF and TPS connector switch pins, made sure the connectors were firmly in place, and that problem disappeared! Idle was around 1000 as usual.

Returning from a 140k drive each way last Saturday, cruising along at 105, air con on, the
engine seemed to stumble for maybe half a second (at the most), and the "check engine" light momentarily flashed on. The car ran fine after that, another 60k or so, except my wife told me she thought she detected an electrical burning smell in the car straight after the engine hesitation.

And now it won't idle. Holding say 1000 rpm with the accelerator, easing off slowly results in the revs smoothly dropping until it stalls. No sign of any engine miss at any speed.

I noticed that holding the revs steady with the accelerator at 1000 rpm, turning the air con on causes the revs to drop to around 800, where it stays, returning to 1000 rpm only when it's turned off.

A couple of seconds after turning on the air con, the interior light (I had the door open and it was almost night) flickered. Not much, but enough to notice.

I've checked the sensor connectors again, they look fine. No indications of burnt wiring.

Anyone recognise these symptoms or have any suggestions where to start looking? I'd rather not just throw new parts at it until the problem goes away, as I am out in the sticks and getting spares is not as convenient as living in the big city. I have a multi-meter and as a first step I'll check the TPS tomorrow.

Any assistance will be appreciated!

Life
18-11-2008, 06:52 PM
Check your ECU fuse, ECU remembers how to idle... Happens everytime I do a reset.

Fuse is located in the fuse box above the battery, there are 2 IIRC.

Also, any leaks?

Whats the fuel guage reporting when in the ON position?

MitchellO
18-11-2008, 06:53 PM
Could also be a defective battery.

EZ Boy
18-11-2008, 07:20 PM
Check all your leads clicked on correctly - namely the MAF lead and ISC lead. Did you retighten the clamp on the inlet piping at the TB?

Unblock / clean your PVC valve on the front tappet cover, driver's side. Little black plastic elbow - clogs up and aids stalling and poor running. Check you've reseated the plenum and TB correctly.

Btw, bad idea to clean the MAF sensor. Nothing good seems to come from fiddling with them.

SuperMonkeyKing
18-11-2008, 08:22 PM
Check the connections and soldering to the ECU itself.

OldOne
23-11-2008, 02:22 PM
Thanks for the ideas, people.

I got a chance to look at it again today. No hoses left off, clamps firm. Sensor
connectors snug. PCV valve is clean, rattles when shaken, its hose isn't blocked.
Removed ISC to have a look at it. Not gunked up. There is power at the connector
pins. Got my wife to turn the ignition on while I looked at it, it made a short noise,
halfway between a click and a bzzzt, nothing moved. I've no idea if that is normal.

Hopped in the car to give it a spin, engine runs nice and smooth. Still wont idle, although
it seems to be more reluctant to stall. Sort of hestitates at 300 rpm before giving up and stalling.

I'll put in a new TPS and ISC, the car is 10 years old and these sensors don't last forever.
The fuel gauge indicates about 3/4 full, which is about right.

The parts will need to be sent by mail, hopefuly before next weekend.

I'll post again when I give that a try!

Ers
23-11-2008, 08:00 PM
It shouldnt be the TPS, as these arnt cheap, get another one from a wrecker if you really need to remove the TPS as part of the issue.

TPS's generally will fail where the throttle spends the majority of its time, between 20-50% of throttle, not at idle.

ISC could be the issue, and is more likely than the TPS.