Kangarooing and hunting when warm

[Steve205 18 1 Cars]

Good afternoon all.

 

1989 

205 1.6gti. 

Oe in every way possible. 

No pas/ no aircon

 

 

Help needed. I booked my NCT (mot) for Tuesday. 

 

Car has suddenly started acting up. Hunting about 250rpm while warm and kangarooing like crazy at times at low speeds especially in 2nd/3rd gears. It is intermittent.  

 

She has always hunted when cold started since I bought her 6 years ago.  Once throttle feathered for a minute or two she always used to idle smoothly.

 

While cruising at higher speeds she feels wavey but no dials are showing this hesitation.  

 

When being driven on all hesitation seems to disappear. 

 

Nothing has been altered in her set up in last year.This has developed in last few days. 

 

I was on a road trip last weekend (400+miles) and all was good until she started this on way home. 

 

Any ideas as to the most likely cause?

 

All air intake pipes on top of engine are in good order and tightened in place. 

 

Thank you 

Stephen 

[Leslie green 165]

When started from cold the "sad" valve should operate to bring the idle up to 1500 rpm for a minute or 2 until things warm up ,it sounds like it has never worked and could not be stuck open allowing extra air in all the time if you now have a high idle .You could cap of the end of the sad pipe near the battery but you also need to cap the bellows it fits into to eliminate the sad altogether for testing , its only used during warmup anyway. Metering the sad valve pins with a multimeter will give you a resistance reading if its out of spec its for the bin. The spec in in the haynes manual which if you haven't got one buy one of ebay as it will be a great help.

 

Its just as likely a hose has split not an air intake one  unless its the boot  after the airflow meter or an oil breather hose down the front of the engine making the car run very lean . Once it goes for Nct you should see what the co reading is , it should be around 1.5% if its very low that would point to an air  leak causing a lean mixture.

A failing airflow meter could make kangerooing a lot worse too if the track is worn but id look at cheaper possible causes first. Its not likely to be that easy to find the problem but the co reading will be a start. Mines hunts a bit too when warm and I suspect the dissy is worn but otherwise it runs ok with some shunt at low speed at times when you come on and off the gas at low speed  and as they say they all do that !

Edited Saturday at 05:28 PM by Leslie green

[Steve205 18 1 Cars]

Thanks Leslie.

 

 

After cold start and initial feathering of throttle rpm does go to approx 1400 and then eases back over a few minutes to approx 1000rpm.

SAD was checked when 1st bought and seemed to be functioning ok.

 

I feel it could be an air leak in a breather hose that I can't see. 

 

Good point on the co reading.  It will be a good starting point.

 

The fact the faults are intermittent are what's confusing me. 

 

Thanks

Stephen 

 

[Leslie green 165]

Id have a look at the rotor arm and cap for cracks and inside the dissy for oil too as an o ring can leak , intermittent faults can be a real pain especially old cars with no fault codes to read and just because the sad was working 6 years ago it may not be now and may only close sometimes but if it goes to 1000 rpm that's not bad at all.

Edited Saturday at 06:31 PM by Leslie green

[ALEX 103 1 Cars]

The hunting symptom sounds fuelling rather than ignition.

If you eliminate air leaks, poor fuel pressure. and the ECU Coolant temp sensor, id next look at the AFM.

Faults I've seen are bearings for the flap go stiff and the tracks on the ceramic plate wear out.

There's instructions on how to bring some life back into an old AFM (I think on the main 205gti drivers site).

But id look into buying a new or reconditioned one, it's always worth having a spare on hand.

  

The kangarooing could be fuelling aswell, but could also be a poor ignition connection.

a common fault is the distributor fly lead to the ignition module. 

Also check the obvious stuff HT leads , plugs, dizzy cap, rotor (as mentioned above). If they're due a service it'll be worth changing them anyway.

 

Edited 8 hours ago by ALEX

[Steve205 18 1 Cars]

Monday evening the car was making all kinds of trouble. Backfiring and running very lumpy. Seemed to be running on 3 cylinders. 

Checked obvious things.

Was making good spark at ht leads. Distributor looked relatively clean and no cracks or oil.

Removed plugs. Chambers 3 and 4 looked oily and these 2 plugs were sooty.

Test was at 10.30 the following morning. 

Rushed to motor factors at 8.30 that morning and got 4 bosch plugs.

Swapped them in.

Car ran perfectly. 

 

Sailed through test mechanically. 

Was failed on rust in footwells.

 

Due to get this resolved as soon as possible. 

Then give her a full service to see why cylinders 3 and 4 are oily and fix this then. 

 

The never ending roulette wheel of 205 ownership.....

It's all part of the fun....at times!

 

Thanks for the advice. Really appreciate it.

 

Stephen