T16 Running Problem

[Stevo309 0]

Took the 306 out the other day after being in the garage over winter and after just a couple of miles I noticed that the tick over had gone very high (2.5k). After parking up this dropped to around 2k rpm but it was hunting +\- 200 rpm. Once I switched it off it wouldn't start again. I unplugged the ecu to reset it and left it to cool down and after about 10 mins of turning over persuaded it to start and drove it home. Whilst driving home it had the same high tick over but otherwise seemed ok, absolutely fine when you booted it etc. It's now back in the garage and won't start.

 

I'm guessing a sensor has gone, tdc sensor possibly? Does anyone have any ideas and suggestions on what to test and how please?

[M@tt 77]

if TDC sensor had gone, it wouldn't run at all.

 

High idle would indicate to a possible airleak, get some easi start and spray it round the inlet tract throttle body and onwards and see if that caused revs to rise even more, f so it indicats unmetered air is getting in

[Cloverleaf 1]

Completely off topic but I didn't know there was a T16 engined 306 in Banbury...pics please!

 

 

I also agree with Matt as a good starting point (no pun intended)

[Anthony 1,003]

Faulty coolant temp sensor possibly if it's not an air leak as suggested above?

 

Not sure how the T16 ECU reacts if the sensor is disconnected / gives no reading, but I'd imagine that a sensor reading (or the ECU believing) that it was extremely cold outside would result in significant cold start enrichment (possibly enough to cause flooding, hence the non-start issue) and high idle speed.

 

From memory, a working coolant temp sensor should read something around 2.5k ohmn at 20 degrees C, and lower resistance the higher the temperature.

 

Different management, but I know whenever my old Mi16 had eaten its dizzy cap again I'd initially get very similar symptoms to what you're seeing - very high idle speed, intermittent/difficulty starting, and poor idle/low speed running because the ECU was just pouring fuel in (to the point of occasional black smoke out the back). Clearly a T16 doesn't have a dizzy cap, but I wonder if something else breaking down could result in the ECU getting very upset as mine used to.

[Stevo309 0]

The problem will be getting it started though to test air leaks. TDC sensor went before and it wouldn't start at all you're right but i wondered if there are degrees of fault with them so it may be partially sensing the crank position? Not sure why that would cause it to tickover faster though.

 

Would an air leak prevent it from starting? I honestly could turn it over for 10 mins now and it wouldn't fire. I was lucky to get it home at all. At least it saved itself and me from the humiliation of an AA trailer ride home!

 

Pics below as you asked :-)

 

 

[Stevo309 0]

Not sure how the T16 ECU reacts if the sensor is disconnected / gives no reading, but I'd imagine that a sensor reading (or the ECU believing) that it was extremely cold outside would result in significant cold start enrichment (possibly enough to cause flooding, hence the non-start issue) and high idle speed.

 

Yeah i did also wonder about this it was acting as if it had "a load of choke". This sounds odd but i have no sense of smell and was on my own so I couldn't tell if it was stinking of fuel and was flooded.

 

Thanks for the info though Anthony, i can put a meter across the coolant temp sensor anyway

[24seven 104]

If it's flooding then disconnect the injectors and try and fire it up, if it fires you're obviously getting spark and with the injectors disconnected it'll only be burning what fuel was already there. My mate's TU engine'd 306 kept flooding and cutting out once it got to around 70*C, replaced the CTS, problem solved.

[dcc 855]

had similar problem on a gti6 engine before, check map sensor is clean, and if you have one, check the cam sensor.

[Tom Fenton 1,548]

High idle indicates extra air is getting in somewhere, if there is no extra air all the fuel in the world will not increase the idle speed.

 

I would firstly check and double check that there are no pipes off anywhere, even a small signal pipe would admit enough air to increase the revs.

After that check the idle valve for muck or sticking, also check the boost control valve as this can potentially allow air into the inlet manifold without metering it.

[Anthony 1,003]

High idle indicates extra air is getting in somewhere, if there is no extra air all the fuel in the world will not increase the idle speed.

The ICV opening further would though... but I do agree an airleak sounds more likely, especially on a engine that uses map as primary load.