MFTS warm up cycle 3b

[Monkeymagic]

I’ve recently had a couple of niggles with my 3B which I have ironed out by replacing the ignition components. However she is running great but on occasions after a minute or two following cold start up does a little cough or two. It’s defo temp related and I think im right in saying the 3b uses the MFTS to send temp signals to the ECU as well as gauge and overheat boost cut..
Has anyone had a similar issue with their 3b and where is the best place to get a MFTS from now. I think mind is a BEHR or MAHLE and I replaced it shortly after getting the car…
my running issues started after not using the car at all for 18 months as I was too busy with life/work. As I took the car for the mot in June she just about scraped through emissions which I have never had an issue with before. Then on the way home developed a misfire at 3800 rpm then was running on 4.5 when I got home.. As I say there was corrosion on all 5 HT leads at both ends. New cap rotor arm leads and plugs resolved this..

[newsh]

Hi Monkey
The MFTS only does the dashboard temp gauge and switch duty for the autocheck over-temp warning and boost reduction.

The ECU uses the little white temp sensor on the back of the head for warmup mixture adjustment. These are cheap and readily available. My 3B had a wiring issue inside the sensor connector boot, insulation crept back and wires touching, worth a look. You can read the temperature measured by this sensor in Vagcom measuring blocks.

[Monkeymagic]

From the literature I’ve read the 3B doesn’t have the 2 pin ECU sender. I’ll go digging and find ot

[newsh]

From the literature I've read the 3B doesn't have the 2 pin ECU sender. I'll go digging and find ot

Definitely does

[newsh]

[Monkeymagic]

Thank you Newsh, I have been out in the car this afternoon and she ran like crap again. Low boost on cold start, full boost once warm, however extremely lumpy idle.
I unplugged the G62 and there was no difference, however unplugging the MAF smoothed the car out, it was still not fully smooth but better. With the MAF plugged in there is a distinct stumble similar to a misfire.
With the MAF unplugged she ran on all 5 but still lumpy. I’ll have to clean the MAF pins next..

[newsh]

Could be a MAF hose leak or a leak in the PCV piping. Unmetered air getting in. Disconnecting the MAF the ECU will apply a fixed value.

Or could be a bad Lambda.

Definitely clean MAF pins but on the 3B usually it will give you a hard boost cut then limp mode till you reset the ECU by switching ignition off and back on, or sometimes it will just feel off and lacking power.. 3Bs are weird..

Would be great if you could get Vagcom on it and pull codes.

[Monkeymagic]

I’ve had it had it hooked up to VCdS and the only codes I got were open circuit or low signal codes due to me unplugging stuff.
I did have a mixture regulation code, I then realised I could hear a huge vacuum leak. The pipe from the inlet manifold to the evap valve was hanging loose. They are all Roose silicone hoses but this one does not like to stay tight despite a new jubilee clip. Once I pushed this home she was purring again and the Co reading sat at 1.2%.
I watched the MAF reading in window 00 field 2 and it sat at 24 . I have also cleaned the pins with alcohol. They were filthy..

[Monkeymagic]

It was definitely lacking power on the outward journey , this returned on the way back, I suspect this was due to unplugging the MAF which would have reset after engine wa turned off as you say..

[newsh]

Ah so a leak at the inlet manifold.
Seems counter intuitive but you could try spraying a little wd40 on the pipe before sliding the hose on, it seems to help them stick. Works on handlebar grips on the motorbikes. Hair spray works too.

It would be worth doing another boost leak test just to be sure but it seems like you found it.

[Monkeymagic]

I’ll give the hairspray a go. We used to use it on mountain bike grips. It’s all lock on now thankfully.. I’ve got a smaller diameter jubilee too.. I’m getting good vacuum and boost readings on my gauge now.

[Monkeymagic]

The issue was a weird one, the “hi grip” jubilee clip I used was too wide. As I tightened it it was pressing on the bevel edge of the vacuum port on the intake, as it tightened it walked the hose off. I used a narrow width jubilee and it tightened nicely between the inlet manifold and the flared tip giving a tight fit.. she still seems a tad lumpy but I wonder if I’m being paranoid.
she has always had a slight fluctuation at times during idle.
im going to put some miles on her when the weather improves.
I have noticed the Bosch 044 pump is noisy too, I may need some extra fuel..

[Monkeymagic]

I’ve taken the old girl out this evening and she’s back.,,.. hopefully that’s it, until the next time.

[newsh]

I've taken the old girl out this evening and she's back.,,.. hopefully that's it, until the next time.

Great news mate, they're great when they're on song eh?

[Monkeymagic]

Absolutely, but frustrating in equal measure..