A3 First start of the day poorly.

Sharkie1976

Sharkie1976

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Hi all.
Car beginning to start rough first thing in the mornings. Fine afterwards for the day unless left for 6-7 hours or overnight.
Audi A3 2.0tfsi 2007.
Becoming very regular now.
See video, any good ideas?
 
Hi mate. Yes, I have vcds that shows no faults. What do I need to check during start up? Thanks
 
First port of call be stuff like engine coolant temp, fuel rail pressure, engine speed/position.
My old 2.0 AXX had an HP pump with a faulty metering valve that caused poor starting...hence importance of fuel pressure.
 
Checked those before and check out ok. CTS has already been changed and temperatures are good. FRP is good, came back from 2 week holiday and fired up straight away, so don't believe it's fuel draining back either tbh. Crank sensor also new, and still the problem persists
 
I have a data log that I recorded (38mins journey to work). Would you be interested in looking at it if I email it to you.?
 
Flight data from journey isn't really helpful here.
Before that, are there any consistent ambient conditions when fault occurs...e.g. just noticed on colder mornings/car left in sun?
 
Ok no worries. It tends to happen when damp or cold mornings mainly, but has also occurred in nice weather temperatures (not as common tho) I've bench tested the AIT sensor and that functions correctly.
 
Isn't AIT integrated in air mass on this one? In any case, AIT isn't part of the map for startup fuelling. Also, better to read the signal from this sensor while in place in case car-side wiring is at fault.
 
No, it plugs into the front of the engine at the intake manifold. I checked voltage (car side) and that reads true, 5 volts and an earth if I recall.
 
Ah, ok.
So the signal for AIT reads fine. Good.
Stuff like plugs all good?
I watched you video again and the sluggish starting looks symptomatic of pump metering valve issue. So its got nothing to do with fuel running or not running back to the tank. Even if low pressure supply holds all day long and is bang on, when you crank if the metering valve bleeds too much fuel back on the return, you're not going to get correct mixture for cold starting. Assuming the basics are in place, HT, compressions, low pressure fuel supply, throttle plate condition, essential signals, etc, I'd want to scope the metering valve and check the duty and current ramp...make sure its moving okay.
 
Yes mate, plugs, coils are good, changed plugs (ngk platinum) and new coils in the last 6 months. On vcds if I blip the throttle on and off to say 5000 rpm it does register a single misfire on random cylinders, but none whilst driving. Is this metering valve part of the hpfp? It's strange tho how some days it can be pretty chilly but fires up first time. The joys of an intermittent problem huh
 
Throttle body plate is nice and clean, basic settings carried out on vcds too.
 
Sharkie1976 said:
Is this metering valve part of the hpfp? It's strange tho how some days it can be pretty chilly but fires up first time. The joys of an intermittent problem huh
Click to expand...

It is i'm afraid. If you PM full vin i can pull some info for you.
Intermittent faults....tell me about it! :S

Something else to try is blanking EVAP (though this is normally sunny-day-related, but worth a shot for sure). They purge valve can f-up and mess up mixture...most noticeable during starting.
 
Hey I tell u what.! I have previously had a code for the evap, think it was P0441. How can this influence a poor startup? It was logged in memory when I first got the car, no eml. Cleared all old codes and was fine. Did get eml about 6 months ago for the same code. Again, cleared it and it hasn't come back since. Do u think it's worth looking in that direction?
 
By the way. I have changed the purge valve N80 I think it's called, but didn't do anything with the canister.
 
It effects starting due to tank vapour being added to the mixture at the wrong time, i.e. starting.
I'd first blank off the evap input to the intake (of course capping of the manifold as required to prevent air leak) and see if this remedies your intermittent hard starting - this may log an evap fault code.
If this sorts it, the evap system should be scrutinised, and the canister should be renewed.
 
Sounds like a good plan mate. I'll take out the purge valve completely, then clamp off the hoses before and after where the valve was. Does that seem a good way to do it?
 
Ideal. Remove the purge valve and cap off the manifold-side pipe. Don't cap off the tank side - this can vent to atmosphere like the bad old days (just make sure it's not pointing towards exhaust manifold or anything hot). Pipes are the hard plastic type so clamping not an option, capping only.

Let me know how you get on mate.
 
You've been a great help. Thanks very much for your guidance. What can I cap it off with? Anything that will fit into the hose I guess (pen lid, lol?). Do I need to disconnect the electric cable on the valve? or just remove valve completely along and angle hose away from manifold?
 
You're gonna need something that's a good fit as you want it to hold while you test over a number of days. You don't want it falling off as that will cause on hell of an air leak. We have the luxury pro kits here so unfortunately I can't advise on a good "make-shift" alternative. Goes without say, and I'm sure you're aware, but be extra careful not to let anything get sucked in to inlet when your trying to find suitable cap.

I think the purge valve is an NC (could be NO, not 100%) type so leave it disconnected (electrically) and still connect to canister to prevent purging to your engine bay. I wouldn't advise capping off for longer than is required to rule out (or in) the EVAP system for your hard-starting fault.

...and you're welcome! All the best!
 
Last edited:
Cool, thanks. I'll have to take a look around to see if I can find something suitable. Am I safe to drive with this hose capped off? and do I need to remove the purge valve completely or not? You're a diamond. Thanks again.!!
 
Sharkie1976 said:
Cool, thanks. I'll have to take a look around to see if I can find something suitable. Am I safe to drive with this hose capped off? and do I need to remove the purge valve completely or not? You're a diamond. Thanks again.!!
Click to expand...

Personally, I think if you are able to securely cap the intake, then yes, that's safe to drive. If it's not secure or comes free when driving, pop the pipe back on to the purge valve to get you home and re-think.
 
Splendid. Just so happens a guy at work has a bag full of various caps and plugs that I require . The only other thing I wanted to know was....can I attach a long piece of hose to the end of the purge valve and run it into the atmosphere or do I need to disconnect it altogether? Cheers mate
 
Sharkie1976 said:
can I attach a long piece of hose to the end of the purge valve and run it into the atmosphere or do I need to disconnect it altogether? Cheers mate
Click to expand...

Yes, if you are going to go the extra mile and route the purge pipe out of harms way with a hose, then you can leave the purge valve connected (electrically) to keep the ECM happy.
Your attention to detail here is admirable but don't get carried away modifying your engine bay for a "quick test" :D
 
Cool. I'll get that test up and running as soon as I get a chance. I'm only re-routing as u said to keep it away from the manifold. I don't want to go up in flames, lol. I have robbed a piece of hose from work so no cost to me, lol. Many thanks again for your help mate. I really appreciate it. I will of course update u when I have tested it. Take care geezer.!
 
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fouryoghurts said:
You're gonna need something that's a good fit as you want it to hold while you test over a number of days. You don't want it falling off as that will cause on hell of an air leak. We have the luxury pro kits here so unfortunately I can't advise on a good "make-shift" alternative. Goes without say, and I'm sure you're aware, but be extra careful not to let anything get sucked in to inlet when your trying to find suitable cap.

I think the purge valve is an NC (could be NO, not 100%) type so leave it disconnected (electrically) and still connect to canister to prevent purging to your engine bay. I wouldn't advise capping off for longer than is required to rule out (or in) the EVAP system for your hard-starting fault.

...and you're welcome! All the best!
Click to expand...
.....
Sorry mate. I kept asking about leaving it plugged or unplugged, and didn't see the second half of this message originally. Sorry I kept asking this question, lol
 
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