Macster

The misfires have returned. Same scenario as maybe as many as 6 times before: After the weather has turned off a bit humidi/muggy since the last time I drove the car, in this case which was day before yesterday, upon the 1st cold start of the day after a moment or two the CEL comes on.

Oh, first the car: 2003 996 Turbo 6-speed, stock, was parked under a carport.

Upon cold start wasn't paying much attention to the engine as I wanted to back the car out from under the carport rather than let the engine idle a bit. I wanted the car out in the clear, so to speak, because I wanted to hear the latest traffic report on the radio and the carport interferes with radio reception.

So I backed the car out and pulled it forward a bit and parked out of the way and was listening to the radio when about the time I think I noticed the engine was idling a bit rougher than usual I hear a chirp and after a moment looked at the dash and noticed the CEL was on with the warning message displayed on the dash.

Whipped out my OBD2 code reader and sure enough: P0300, P0303, and p0306.

Just had new coils and plugs installed at the last service which was done at just over 140K miles. Car currently has a bit over 141K miles.

My thinking was the original coils were getting along in miles and time and were the source of these misfires, the same ones. In another thread I posted the dates but I don't have that info now.

The engine has never misfired when hot under any kind of usage. It has misfired once when left out in the rain and again when left out in the fog, but I have left it out in the rain since the new coils were installed and it has not misfired.

Not sure what is going on. Could be just an artifact (?) and nothing to worry about. Engine is noticeably smoother and feels a bit stronger too after the plug/coil change.

Drove the car around 120 miles Sunday and the engine was just fine.

Will have to think about this some I guess.

Kind of wondering if maybe the MAF could be a problem? No other error codes. No pending error codes. But I wonder about the MAF's service life.

While my Boxster's original MAF is fine with way more miles on it I note "identical" items on the Turbo have a shorter life span than they do on the Boxster. I will have to think about the MAF some more...

Thankfully the engine doesn't manifest any other symptoms. So unless it does I'm not going to worry about this much.

docboy

Mac, which OBD2 reader do you have? Amazon has an Autotel AL519 I've been looking at.

highlander

How is your battery? Do you leave a tender on your TT when it's laid up for a while? Low battery voltage causes all sorts of weird and wonderful false triggers.

cdk4219

Possibly remove them and slather in dielectric grease. It has aided damp misfires for me in the past.

Macster

An Actron model, but don't ask me the module number. I'll have to walk all the way out to the car as I can't remember the model number to save my life.

Had it for years. Doesn't support CAN. (When I had a CAN car -- GTO -- I bought a Predator to use to communicate with the GTO.)

The unit has proved to be invaluable and paid for itself many times over.

I know nothing about the Autotel units. Oh, I've used Auto XRay devices. We have a couple at the office. Really like my Actron unit though.

Macster

The battery is ok. I drive the car every other day. Just had it out Sunday for a 120 mile run. Then drove it Tuesday to work and back -- 30 miles each way -- and then drove it again today to work and back. 'course, the misfires occurred this AM as I was leaving for work.

When my Turbo's battery gets low the radio acts up. It will come on when I start the engine but not on a set radio station but at some random point on the dial. (Showing my age...) Or sometimes it will be on a station but no sound comes out. Only way to "fix" this is to turn the engine off and wait or -- so I've been told -- pull the radio fuse. Too much trouble to pull the fuse and often I do not have time to wait for the radio to recover so I just live with a dead radio for a while.

When the battery is really low I've seen the trip odometer zeroed.

But I'll keep the battery in mind.

Macster

I can't get to them, but I'll touch base with the SM and the techs and see what their thoughts are on using the dielectric grease. If they think it a good idea I'll see about getting this down the next time I have it in for service.

cdk4219

[QUOTE=Macster;13075079]I can't get to them, but I'll touch base with the SM and the techs and see what their thoughts are on using the dielectric grease. If they think it a good idea I'll see about getting this down the next time I have it in for service.[/
Possibly the least expensive remedy, but the fact that you replaced them very recently would not make me want to replace them again. It could possibly be the primary connector as well.

gophaster

Have you tried disconnecting MAF for a while and see if there are any changes. You could also test MAF with volt meter to see if it's in spec...

Pull up the rubber boot covering connections on MAF. You will be testing the pin furthest away from you when standing behind the car. Use the grounding lug of the fuel filter that is near by for ground.

With car off but ignition in position 2 you should get between .9 and 1.1 volts.

Then start the car and get it warmed up and test voltage again. Now you should get 1.2 to 1.5 volts.

Macster

The tech said that since the misfires are lean misfires -- the CEL is not flashing -- and the engine never misfires at any other time, he believes the cause is a couple of "sticky" fuel injectors. They start out sticky not working 100% but recover after a bit of idling, but not quick enough to avoid triggering a misfire.

His suggestion was to use a bottle of fuel system cleaner, engine cleaner in the fuel tank. He gave me a bottle of the Swepco stuff.

The bottle is enough to treat two full tanks of fuel but the tech said to just use the entire bottle in one tank. So I dumped in the entire contents of the bottl and topped up the tank, which was down about 4 gallons from full.

I'm driving the car today and am anxious to see if there is any change in the engine's behavior, not that it is acting up at any time, other than the every so often rough cold start which can in some cases trigger the CEL.

I video/audio recorded today's cold start and while the engine felt a bit rougher than "usual" the CEL remained off.

Kevin

Ask your tech to check your Fuel Pressure... If you have a sluggish fuel pump or leaking check valve on the return side, you "can" get this..

If you have a minor split in one of the fuel pump "lines" you have all the fuel leaking out and then lean on start up.

Macster

Thanks for those. I'll keep them in mind if the misfires return.

I'm about 1/4 of the way through the fuel tank into which I dumped the Swepco fuel system cleaner.

Will probably run the rest of the fuel out before Monday.

Macster

Really though the engine was not running that rough and the CEL kind of caught me by surprise.

'course, I didn't even think to make a video/audio clip of the cold start and idle time.

Anyhow the same codes as before.

I'm around a 1/3rd way through the tank with the fuel system cleaner added and I'll go ahead and run the fuel level down in hopes it does have some benefit.

Macster

Leaving the office around 7:30pm and fired up the engine and letting it idle and while the engine was not really running that rough and the CEL came on. Same error codes.

I've used up the fuel with the fuel system cleaner in it. I'm reluctant to try a bottle of Techron just now as I do not want to have to change the oil again so soon after just having it changed a few week ago. I haven't even put a 500 miles on the car since then.

I think the problem is getting worse. For one thing the misfires are occuring more often. Used to be weeks and weeks between events. Now the events are separated by just a few days. Also, yesterday was the first time the misfires occurred so soon after having used the car. I drove it for lunch about 6 hours earlier, around 1:30pm. While the engine wasn't warm it wasn't dead cold either. Before I'd have to leave the car sit a night and a day and another night.

Engine still runs just fine on the road.

I'll wait until the senior tech returns from training. He's due back to work Monday. I'll touch base with him and see what he recommends. New injectors? Or perhaps what Kevin mentioned in an earlier post?

Van1

Bad DMF? Had random misfire CEL situation on my previous 993. Changed plugs, caps, rotors, wires, etc and would still get them. Changed out the DMF for a LWF when the clutch went bad and never got a random misfire CEL again.