HI Guys,,
I have a problem that my dealer doesn't want to solve due to my modifications on my car..
In cold weather only on first cold start up only, but not everytime,
The engine idles very rough for the first few minutes ,like missing almost,,and then the light comes on and the drive to shop memo comes on.
BUT after another several minutes when as it warms up it smoothens out and the car runs perfect and perfect normal power,,It was data logged to verify when fully warmed up that what was checked was in range.
The code is misfires in most of the cylinders...I know its not this, coil and plugs were changed before and I put a new battery in also.
I almost believe its maybe a lean condition of some type?
Maybe something related with secondary air pump?
Thanks for any input..

 

When did the problem show up? Plugs and coils swapped but with what? New plugs that are perhaps too cold might still have issues for instance. No misfire under load warmed up?

 

HI, No problems ,no miss fires ,,runs great after several minutes from cold start idle...Data logged confirmed everything was fine after warm up.
Plugs+ coil replaced recently...
Thanks

 

i would imagine johns running one step hotter plugs? but agree.. if not? .... weird that nothing shows up in logging. i would immediately go right back to plugs n coils tho.....

 

Does your car still have MAF?

 

.
Hi,Thanks for input,
It is not coils and plugs..If that were the case it would do it all the time and show on Data Log..Car pulls 1.4 bar and hauls,,no problems.
Also I think you met one step colder instead of hotter..

 

Yes..
MAF is working fine.

 

do you have a Durametric?
Shut-off the SAI when you fire it up to see if anything improves.
Also capture a datalog of the fire-up

 

yes, of course was walking and typing lol thx for correcting me. I meant by way of example using the Bosch FR-6-LDC ( gt2 ) instead of the 5 ( stock 996t ) series. but I see youre using those fancy denso's? about which I know nothing of their heat range numbers.

 

My Audi tt does the same thing and so far its always been the MAF, runs rough at start up and then better when warm new MAF I'm good.

 

I didn't ask if the plugs were new, plugs that are too cold can misfire even if brand new and then warm up to run better. It might be worth swapping in plugs closer to stock, even if used, to see if the problem goes away. When did the problem begin - was something changed just prior or did it simply begin? Weather change?

 

My first impression is it reads like either the coolant temp sensor is reporting too high a temp or the intake air temp sensor -- part the MAF -- is reporting too high a temp.

The result is the engine is not fueled properly for its actual temperature, in this case it is fueled too lean.

If you tell me the engine spits back in the intake that's a sign the engine is running lean.

Upon a cold start you can look at the coolant and intake air temp readings and confirm they are close to ambient and that they behave, do not suddenly jump (or drop). Continue to watch these and if one of these sensors is the problem I think'll you see enough to make the diagnosis.

 

Thanks,,I think that is a step in the right direction...And it makes sense to look at those..
Because the dealer after all there diagnostics believes its lean fueling problem also..But the cause at only cold start up in the cold with no other codes is the problem...
Markski did the data log back after it first happened but it was warmed up and it showed everything was right on..As I said it has to be real cold out and sitting for a few days to happen.
He thinks it maybe a vacuum leak in the hoses that work with the secondary air pump so the next thing is he is going to do a pressure test and we shall see..I hope it is that simple..
Besides what you mentioned,, Maybe a bad secondary pump rely or a crank sensor might cause a lean condition or misfire at that initial start up from what I researched ? But I was told there would be codes showing,as for the pump also?
If its in the upper 30s or driven daily with normal cool downs after the intial start up problem in colder weather it doesn't happen...
All in all my car has been great in reliability and now to get something out of the norm isnt that bad because after those several minutes it runs great..

 

Bump...
If you don't that's fine, but would be good to know...
Another way to test your coolant temp. sensor if you have a basic OBD2 reader is to start the car with MAF disconnected(or similar to replicate fault code) and read the freeze frame data, it will tell you the coolant temp readout...

 

My car had the same exact issue when I bought it, then I found that the vacuum hose from plenum to fpr was disconnected at the plenum side. Could be a possibility!