Unusual Lag and cutting out

[20Vcqdriver]

OK. My Cq has been running well upto about 2 weeks ago and now has some unwanted characteristics. At anything below 3500rpm there is at least a seconds worth of lag before boost builds and the car shoots off down the road (not normal for a standard K24). Also, on cooler mornings the car will intermittently cut out as I back off to slow for roundabouts or junctions and have to re-apply throttle to catch it before it's too late. Any ideas welcome

[Jamo]

Tbd

[driftin jo]

you need to pull the fault codes,
it could be the MAF sensor, or numerous other things, boost leak etc.

[Ian Simmonds]

you need to pull the fault codes,
it could be the MAF sensor, or numerous other things, boost leak etc.

Quite a few of the 20vT conversions into type 85's haven't kept the VAGCOM link, as maintaining it (like we did on the RallyRep) requires full understanding the wiring and the provision of the connection port. It's not a 'given' for a 20vT type 85 to have active VAGCOM.

[20Vcqdriver]

I have the facility to read the fault codes as made sure to keep the ports behind the glove box during the conversion, so will get them read at Tim Coopers.
Hoping someone had this issue themselves at some point and could do a quick fix. Once it does boost and the water injection kicks in it rockets down the road but it's not progressive. Basically pretty tame until the last 1/2" throttle travel then shoots off after the 1 sec delay. Still records the same 2.5 sec 50-70mph in 4th and cannot hear any boost leak hissing as I have heard in the past...

[Ian Simmonds]

I have the facility to read the fault codes as made sure to keep the ports behind the glove box during the conversion,

Good lad... Well worth the effort...

Thought if anyone, you'd keep it....

VBR
Ian

[20Vcqdriver]

One last thing I've just remembered, it seems to rev slower. That is when sitting in the drive, flooring the throttle for 1/2 sec and back used to see the rev counter race round to 4k, now it barely reaches 2k... These engines are great when running right but it seems to spend more times not right

[S2central.net]

MAF or TPS unless timing is off would be my suggestion.

[20Vcqdriver]

MAF or TPS unless timing is off would be my suggestion.

I have a spare MAF so will give that a go and test the TPS too.
Seems to have gone pear shaped after a 1 mile blast down the Motorway to catch up with a mate in his A4 when the speedo went off the clock and was still accelerating before I realised and backed off quick before the police saw me.

[newsh]

Definitely check that the timing is on the marks, flywheel, cam sprocket and dizzy. Check dizzy for backlash, has it got a metal gear or plastic?

[20Vcqdriver]

Definitely check that the timing is on the marks, flywheel, cam sprocket and dizzy. Check dizzy for backlash, has it got a metal gear or plastic?

Metal gear, though checking this will be impossible as cannot even see the thing when installed in a type 85 engine bay as battery in the way... took me over an hour just to replace the plug leads last SORN.

[Hammer786]

Had a similar issue with my urs4 recently and turned out to be a dead MAF. MAF would be my suggestion.

[DJones]

With regard to having to blip the accelerator when the revs drop, you need to ensure that the ECU is getting a road speed signal. It alters the characteristics of the idle stabilisation valve until the vehicle is stationary.

With my bottom end being so light it would stall often when pulling up to roundabouts or traffic lights when the lights etc were on, I was advised by Automark that the symptoms would be cured with a road speed signal to the ECU. Its never stalled since.

Again its often missed on a conversion..

Hope it helps.

Darren.

[20Vcqdriver]

With regard to having to blip the accelerator when the revs drop, you need to ensure that the ECU is getting a road speed signal. It alters the characteristics of the idle stabilisation valve until the vehicle is stationary.

With my bottom end being so light it would stall often when pulling up to roundabouts or traffic lights when the lights etc were on, I was advised by Automark that the symptoms would be cured with a road speed signal to the ECU. Its never stalled since.

Again its often missed on a conversion..

Hope it helps.

Darren.

Interesting where does this signal come from normally and go to on ECU? I have a cable speedo so no signal for road speed at present..
Lots to test so far so once I have sorted issues with A4 for MOT I'll get onto the Cq and hopefully find something.

[DJones]

Interesting where does this signal come from normally and go to on ECU? I have a cable speedo so no signal for road speed at present..
Lots to test so far so once I have sorted issues with A4 for MOT I'll get onto the Cq and hopefully find something.

I cant find my pin out for the ECU but on the AAN im pretty sure its pin 50. On the five speed box it receives the signal from the centre pin on the hall effect unit which screws in to the side of the gearbox. With the other two connections being a 12v+ and an earth.

I cant remember the wiring configuration on the 2 pin sensor for the six speed but its similar to the above. When you have it connect to Vag Com you should see the speed rise when driven. As i understand it this then applied the appropriate map for over run until the car becomes stationary..

It certainly seem to make a difference to my car, but my car probably exaggerated the problem due to the light bottom end.