1.8t startup problems.

[seany26]

Ok, this problem has been there for some time now and I want to sort it before the weather gets colder. If the car sits for any length of time at any stage of the day it can take quite a few cranks to get her lit.
It's not just first thing in the morning, can be also be when the car has been run up to temp and sat for 20min.
Things that I've checked are the coolant temp and intake air temp and plugs. All seem to be ok apart from the temp being a 5℃ out this morning, reading 18 instead of what should have been 13 on both sensors. I don't think this would be enough to mess the mix on startup, could it?
This car has also had a new maf and lambda recently also. Swapped the maf with the old one and it didn't make a difference. One thing I did notice about the lambda was that it was reading 70℃ when stone cold, but when it seen some clean air on crank it dropped to what the actual temp was and then adjusted to egt's when lit.

Any ideas anyone, feel free to share what your thinking.

 

[Chriscooke]

Sounds similar to the issue I'm having on my b5. I'm tempted to change the fuel filter next to see if that helps. Will be watching this with interest.

 

[Slinepete]

Crank position sensor if there is one just going off a similar issue I had with a Subaru hope it helps

 

[seany26]

Crank position sensor if there is one just going off a similar issue I had with a Subaru hope it helps

True there is a crank position sensor, if it was going weak maybe not getting the signal until it switched a couple of times.

As for the fuel filter I've already checked the fuel rail pressure and its not running lean so I'd rule that out.

thank for the replies, lads.

 

[dualmono21]

what happens if you get the engine warm and then turn it off and then back on again after a few seconds ?

 

[seany26]

what happens if you get the engine warm and then turn it off and then back on again after a few seconds ?

It will start first time after a few seconds no prob! Leave it for 10-15 minutes and it can take any thing up 2 6 cranks. This morning it started first time cold tho.

 

[dualmono21]

the problem is reminiscant of the trouble with the coolant temperature sensor but if it started first time this morning it probably isnt this
have a you had a look at the fuel trim when starting the car ?
there should be 2 readings one for short term and one for long term if one of these is off then it could cause starting problems

 

[dualmono21]

on my seat leon on this engine there is a secondary air valve which is used when starting the car to blow more air through the cat and exhaust
a lot of owners had trouble with them splitting and not drawing any air through them ..... might also be worth a look if theres the same kinda thing on the audi

 

[seany26]

Ok, this problem has been there for some time now and I want to sort it before the weather gets colder. If the car sits for any length of time at any stage of the day it can take quite a few cranks to get her lit.
It's not just first thing in the morning, can be also be when the car has been run up to temp and sat for 20min.
Things that I've checked are the coolant temp and intake air temp and plugs. All seem to be ok apart from the temp being a 5℃ out this morning, reading 18 instead of what should have been 13 on both sensors. I don't think this would be enough to mess the mix on startup, could it?
This car has also had a new maf and lambda recently also. Swapped the maf with the old one and it didn't make a difference. One thing I did notice about the lambda was that it was reading 70℃ when stone cold, but when it seen some clean air on crank it dropped to what the actual temp was and then adjusted to egt's when lit.

Any ideas anyone, feel free to share what your thinking.

Ok this problem is definitely nothing to do with cold start, three mornings in a row starts first time. If she is warmed up and I leave the car for a s little as 10min I get it cranking its guts out to turn over, it is a really strange one this! Any ideas?

 

[seany26]

the problem is reminiscant of the trouble with the coolant temperature sensor but if it started first time this morning it probably isnt this
have a you had a look at the fuel trim when starting the car ?
there should be 2 readings one for short term and one for long term if one of these is off then it could cause starting problems

What group on vcds should I look at to see this, I am familiar with group 32 which is lambda at idle and partial load.

 

[Slinepete]

Il put money on crank position sensor have you tried this yet

 

[dualmono21]

not sure in vcds sean
i use a differant program for looking at fuel trim

 

[dope]

Light switch? Does it start first time when the sidelights are switched on?

 

[seany26]

Il put money on crank position sensor have you tried this yet

I cant come to terms with it being the crank because the car does start and I'm seeing rpms as soon as I turn the key in vdcs. the vehicle is not dying or anything so it kinda rules the crank out I would think.

Light switch? Does it start first time when the sidelights are switched on?

No took a good few cranks when I just tried it with the sidelights on, wish it was thou because this is really starting to crack me up!the 1.8t really does test your patients!

 

[dope]

Dang - I know it sounds bonkers with the light switch thing but it's a known issue. Was hoping to help.

http://www.audi-sport.net/vb/a4-a4-cabriolet-s4-forum-b6-chassis/133421-headlight-switch-2.html

I feel your pain brother.

 

[seany26]

going to get the battery tested on Monday to see if that's what is causing the issue. I've a feeling that when the battery was run done one time with the boot lid left ajar, this is when it started. only a new battery in march!

 

[seany26]

UPDATE
Battery checked out fine, even tried a 100ah diesel battery in it just to make sure it's not a amp supply issue.
What next, any more suggestions?

 

[seany26]

Bump
Changed camshaft sensor and it made no difference to the hot start, still turned over a good 6 times before kicking in.
This problem also started the time I sent my injectors for cleaning, don't see how it could effect hot starting .

 

[Slinepete]

Yeah but if the crank sensor is not working it would cause it to turn over and over as it doesn't known the position of the crank

 

[Slinepete]

It might well not be anything to do with crank sensor but if everything else has failed could be worth a shot not sure how expensive they are or how much of a job it is

 

[seany26]

I know we're your coming from, it's worth a try. Can get cheap eBay ones that would probably tell a tale.
But all I can say that when logging as soon as I turn the key it picks up the rpms, so that signal has to be coming from the crank sensor. My mate has a tt, I'll see if he is willing to even let me use his crank sensor.

 

[seany26]

the problem is reminiscant of the trouble with the coolant temperature sensor but if it started first time this morning it probably isnt this
have a you had a look at the fuel trim when starting the car ?
there should be 2 readings one for short term and one for long term if one of these is off then it could cause starting problems

I was looking at the fuel trims today after resetting and letting it idle for a while and the short term went to -3.9. Something I've noticed when starting the car hot and logging the injection on time is pulled back when Im cranking for them few seconds.

 

[seany26]

Problem sorted, turns out injector cleaning services are not what they are made out to be, one of my I injectors had a weep and that's why the car took longer to start because the fuel sitting in the intake put the ratio out. The hotter I got the engine the longer it would take to start if it was left sitting, so the heat must have allowed more fuel to leak out.