Cold lean condition/misfire
 

On cold starts, my car misfires while accelerating. I have a wideband that I know is accurate, so I know it is leaning out.

Knowns:
Directly related to heat
Symptoms dissappear after car heats up
Symptoms are less severe/last less time when the car has been sitting outside in the sun all day
Far worse when ambient temps are cooler/cold
Symptoms dissappear above 2k rpm
Far worse in lower gears
I can hold it at an rpm that it would normally misfire at, and the o2's will correct the a/f mixture

I think it could be a gasket that heats up and seals as it expands from the heat. I don't know where that gasket would be though. I have the roush tvs, I'm not sure how exactly it seals down on the engine. There's no leaks anywhere, and my vacuum reads about 23 (whatever units its measured in). I know it's not tune related, it's progressively getting worse over time. Lately, it's been reading pretty lean in first gear at parking lot speeds. I will probably be getting it smoke tested soon but I just wanted to see if anyone had any other suggestions.

I'm sure there's things I'm forgetting. I'll likely be able to answer any question anyone has to help.

Has it always done this or is it something new? I always let me car warm up as it will stumble when it's cold. I'm an old fart so warming up a vehicle is normal for me whether it is fuel injected or carbed. It may be the plugs you are running. Colder plugs take longer to heat up and get within their proper operating range. Until then they may not fire properly. When was the last time you changed or checked your plugs? Removing charge motion plates will also effect the engines efficiency at idle and low rpm especially when she's cold. Like I said though, I always wait until the temp gauge starts to move before moving out. I do with every car I have ever owned.

I'll just list off some answers and then give some input.

)It's not exactly new, but it is getting worse.
)I have changed the plugs numerous times. Started with HT0's, moved to HT1's, Then Brisks colder plugs, then their factory heat range plugs. No change.
)I always let the car warm up, it is undrivable if I don't. I find myself waiting a lot longer now than I used to. Like I said, the problem even is beginning to occur in first at parking lot speeds.
)I just looked into charge motion plates and on the first thread I found, there was a person saying they can malfunction. Could that potentially be my issue? With it being supercharged, is it likely they are removed? I'm not familiar with these, but I will look more into them tonight. Is there a way to tell if I have them without removing the blower?

I should add, when I said "no leaks", I was referring to no fluids leaking. I'm just lost as to why it slightly "fixes" itself when it's hot. I wouldn't think that points to anything electrical. I know my fuel delivery components are good because it runs perfectly in boost. Are there any conditions that would "trick" the wideband into reading lean? That and the gasket expanding theory are the reasons I'm thinking its a vac leak. It's extremely easy to reproduce, it happens every time.

With it being so dependent on heat to run well, I really want to get this taken care of before winter comes. It's noticeably more severe even in 75 degree weather compared to 85-90 and up. I live in FL, so I have a little more time than the northern states.

You shouldn't have charge motion plates in there with the Roush set up. The whole intake manifold has been replaced so they are gone. It can probably be adjusted for in the tune but these parameters should not change regardless of O2 sensor readings. When you start her up cold she runs in closed loop which runs fuel off of a set table. Only when the sensors warm up does she switch to open loop and use the sensors to adjust fuel trims. Have you data logged during cold start?

Here is my take on my issue which differs from yours in that it has always been the same. You go from a stock intake to a forced induction intake which has dimensions and shaped different than the factory engineered intake. Air flows and behaves different in the two. This is going to effect how efficiently it runs during different situations. When you modify car for performance you tend to give up in other areas. Like cams for instance. To get the big HP gains up top you give up idle and low rpm efficiency. The car idles rough and bogs during some high load low throttle applications. Worse when she is colder. So all I'm saying is that going with my Whipple there are certain things I have to give up like fuel mileage and cold start drive ability.

I understand that, but this issue is getting worse. It wasn't nearly this severe a few months ago. That's why I think there is actually something wrong.

When I first purchased my 06 GT, my car had the same cold start issues as your having.. I'd always have to wait up to 15 min for the car to finally reach operating temp before it was driveable, otherwise the car would always end up sputtering and bogging down..

Needless to say, I found out it took the 02 sensors longer to warm up than normal due to the fuel trims not being calibrated properly in the tune which caused the car to run in closed loop longer rather than switching over to open loop to allow for the sensors to properly adjust the fuel trims..

When I switched over to Brenspeed and explained the cold start issues I was having, they confirmed that the fuel trims were definitely not adjusted and calibrated properly and was therefore responsible for my cold start issues..

At any rate, it's been nearly 3 years since upgrading to my Brenspeed tune in which there hasn't been any further cold start issues whatsoever..

That being said, I would seriously consider looking into getting a tune revision from your tuning vendor and also have it checked by a local tuning shop on their dyno as well :dunno:

My car is dyno tuned but I guess I'll have to leave my car with them for a night. I've gone to them before but they of course didn't see the problem since it was all nice and warm. I don't have anything to datalog with so I guess that would be my only option.

Explain to your tuning shop about your cold start issues your going through and suggest to have your fuel trims looked at and also bring up what 07 Boss and I mentioned about open and closed loop.. It also wouldn't hurt to have your air/fuel ratio checked while your car is still cold as well for your own piece of mind :dunno:

If it's getting worse I don't think it is tune related though going over it is not going to hurt. Could be injectors aren't working right when cold but that is a stretch. Could be fueling issue. How is pressure before turning the key to start? We're taking stabs at it in the dark without any data. Data logging during the event is about the only way to try and figure it seeing how you gone through the normal diagnostic and maintenance stuff. You have to see what is actually going on with fuel trims and sensors and stuff. I know how it is.

There is something wrong with my car and my tuner is so old it doesn;t work so well anymore in the data logging dept. I am waiting to upgrade to HP Tuning software here pretty soon but until them I am left guessing also.

Probably already done it but when was the last time you cleaned your MAF and throttle body? You have a PVC system or breathers?

I actually cleaned my MAF just a few days ago. I cleaned the TB the first time I changed my plugs and the last time. I have the PCV line going from the passenger side valvecover to its place on the blower, not too sure about a driver side. There is a breather on the passanger side where you fill the oil. I'm not 100% informed on those, opinions seem to differ drastically on the forums I've read about them. It was on the car when I got it, so I figured I'd leave it.

Is there any sort of data logging software for a mac? I have one of those obd2 wifi things on the way to me to do some monitoring of what I can. I just don't want to go and spend 400 on a hand held when data logging is the only thing I'd use it for.

Your PCV valve is located inside the driver's side valve cover.. The passenger side valve cover is your ventilation side.. For my Saleen S/C setup, I connect the hose coming off the PCV driver's side valve cover to the inlet side of my oil separator and then attach the hose coming off the outlet side of the separator to the intake port of the blower and then run the passenger side valve cover to the air intake tube connected to the throttle body.. Depending on whether your keeping the factory closed PCV system intact or running an open breather system is the question, as I have no idea what your running.. What I can tell you, is that you cannot run open breathers with the PCV system still active.. You either have to disable the factory PCV altogether in order to run breathers or keep the PCV system fully intact by running an oil separator/catch can..

Hmm. Well I'll put up some pictures then.

Orange is what I thought the PCV was.
Green is the breather I think you're talking about.
Blue is what I now believe the PCV is.

https://cimg5.ibsrv.net/gimg/themust...4c6ae7ecc4.jpg

https://cimg8.ibsrv.net/gimg/themust...182f82e513.jpg

https://cimg6.ibsrv.net/gimg/themust...a9d6165f95.jpg

https://cimg7.ibsrv.net/gimg/themust...28fd2c642c.jpg

Orange is your ventilation hose (passenger side valve cover) which is connected correctly into your air intake elbow at the throttle body..

Blue is your PCV line (driver's side valve cover) which is also connected correctly to your blower's intake manifold..

Green is your oil cap breather that replaces your stock oil cap.. This is fine, providing that it includes a one way check valve, otherwise if it's just a breather filter, it will allow un-metered air into the combustion chamber causing a huge vacuum leak and also lean out the air/fuel mixture..

I also have a similar oil cap breather which also includes a billet one way check valve that only allows air to exit when venting the crankcase during WOT and under boosted conditions, otherwise the valve stays closed under normal driving conditions and functions just like the stock oil cap..

At any rate, I would still contact your tuning specialist and get an opinion from them about what they think may be causing your cold start issues..

Make sure that this breather has a check valve. If it is just an open breather it will cause you to run lean and misfire.

That's exactly what I meant by running just a breather filter.. I should've used the term open breather instead.. Anyhow yes, most definitely make certain the oil cap breather includes a one way check valve, otherwise it will indeed cause a huge vacuum leak and also cause the car to run lean and misfire..

I also recommend the CFM billet valve cover breather which replaces the stock oil cap.. it's the same one way check valve breather I've been using for over 2 years now and it works flawlessly..

https://www.c-f-m.com/performancepar...ang-GT-p86.htm

Sorry for not responding, I took a day off from work and all this thinking and went to a place called Bob's River Place. If you're in or near FL I recommend it.

So dumb question, but how exactly do I check to see? I guess you could try to breath in through it but I don't really want to haha. I assume if it isn't just straight through to the filter then it has a valve?

Well would you look at that. I went and popped it off and there's no valve that I can see. I held a flash light to it and you could see the light through the filter from the bottom (if that makes sense).

I'm certainly all for buying the right products, but is there another model you'd recommend? Surly there are other quality parts that aren't $80 haha. I sure am glad you thought of this. I never would have. Although I don't know how this would seem to go away after its well and heated up. I'm no scientist, but maybe it has to do with the idea of hotter air being less dense and having less oxygen molecules? So then the leak is less noticeable? haha I don't know. I'm not going to get my hopes up, but I'd really like for this to be the cause.

https://cimg2.ibsrv.net/gimg/themust...802a6497e8.jpg

Also, I don't know wtf that gum looking stuff is. Maybe glue slowly deteriorating and that's why it seems to be getting worse?

https://cimg0.ibsrv.net/gimg/themust...ee6bfbe649.jpg

As posted before.. Best advice, is seek an opinion from your tuning specialist, as they'll be able to properly diagnose your car and find out exactly what is causing your cold start issues, especially if your unable to datalog..

It quite could be the issue. When your car is cold and at idle it is more susceptible to nuances in fuel trim. When you are in closed loop the computer doesn't make adjustments based on O2 readings, it runs off of set tables. So if your adding more air the MAF can't see it will not compensate for it. When you car warms up it runs off of the sensors and adjusts for a lean fuel mixture. BUT this is not 100% that this is your isuue. If you could data log you could see if your car is making large fuel trim adjustments. Without that knowledge we are guessing.

And yes, CFM is the only place that makes this type breather cap.