T4 starting issue

[BobR]

My T4 (manual 2.5 petrol) has had this issue for over 12mths now. Mostly it starts first turn of the key, but every now and then it will not start without pumping and pumping the accelorator. When it does start, It misses and stalls if I don"t keep the revs up, until the engine warms up, then everything is ok for the rest of the day until its left overnight. I put a new No 30 relay (thanks Jmac) but made no difference. What I have noticed is that it only does this when its raining. In fine weather it starts first turn 99% of the time, but when its raining, or there is moisture in the air, its the reverse, it wont start 99% of the time. If it was my old aircooled kombi, I would suspect the cold start solenoids on the Solex carbies, as the symptoms are the same.
I have taken the van to my mechanic, overnight stay (inside), but it starts for him first turn. He also looked at fault codes but nothing. I have my van parked under a carport (outside). Not sure he uses VAG software, but would taking it to someone who does, shed more light on the problem? Yes, I service regularly with oil change between. Anyone else had a similar problem with their VW?
Cheers.
BobR

[Seano]

It strikes me as an electrical issue that the Poms often whinge about to do with condensation on crud in electrical plugs.

First step is to pull the sensor from the air intake line and give it a clean up with electrical contact cleaner.
Then use some dielectric grease inside the plug to keep it clean. Repeat with other similar under bonnet electrical connections.

[BobR]

I think you are right (electrical issue), I cleaned the battery terminals and pulled every connectors I could see apart for inspection of contacts, and all seem fine. Will look for the sensor and try as you said.
If it was the air intake sensor, would it show up in fault codes?

[vannin]

I have the same frustrating problem!
When I got mine it didnt have an air mass sensor as it had been taken out to fit an air podfilter. I reinstalled a sensor but it pushed the filter down near the fresh air hole in the gaurd. We had a massive storm and it refused to run ,I tried taking the wires off the air sensor thinking it had got moisture in it no luck. The only way I could get it to run was with no air filter at all. so I bought a different shorter pod filter and duct taped over the hole in the gaurd and its been great in most rain but it poured again last night and it played up again. I looked under the bonnet (in the dark) and there was water under the bonnet and it played up all day.
I stopped at the mechanics and they said it could be a number of things such as the leads shorting out. I havnt had a chance to look at it again and it runs sweet when its dry.
Nik

[Seano]

If it was the air intake sensor, would it show up in fault codes?

Probably not.....because it is not about 'no signal'....more a degraded signal which may not trigger a fault. But then again....it is a Volkswagen so one never knows!!

[Golf Loon]

Sounds like a fine crack in the coil. Very common and they are mounted behind the headlight in a silly place on a T4.

Its ok when its dry, but moisture is getting into the fine cracks.

Could also be temp sensor unit, does it blow fuel /smoke out of the back when it starts up cold.

We are in Campbelltown and have all the VCDS software and are familiar with the T4s. Come past for a scan if you wish.

[vannin]

Would this also cause my tacho to play up?
The needle sits at 2000 when the engine is off then operates from there like its the new zero.
Nik

[southernxmx]

my 97 T4 is having the same issues, did it twice about 6 months ago and didnt think much of it, just finished a major service on it (plugs, filters belts and brakes) and its been happening every day. turn the key and it just cranks until i put the boot into it then it fires up, cough and splutters and will either die or keep running. i've had it almost 5 years and it the first thing thats been of real concern.
I have noticed tho since this has been happening the throttle has been very notchy and rough to push in and not smooth like normal. looked at the wiring and all looks fine, doesnt blow smoke first thing and the plugs are burning nicely the only mod is a K&N filter to replace the OEM one but that was well befor the problems started

[Deano]

I have noticed tho since this has been happening the throttle has been very notchy and rough to push in and not smooth like normal

prob needs a throttlebody clean and align.

[Jmac]

Shame it wasnt the relay, but best its in there now anyway. Over the net diagnosis is a shade harder than the real thing, now a little bit of light there as you mention you have to pump he gas a bit, Make sure there isnt any throttle body codes, if it doesnt fast idle then itll be super rich and choke itself, it explains it a bit more seeing it runs all day after that. Faulty coil would show up more so when warm and you would certainly know about it. Does it fast idle on start up mate?
Cheers
Jmac