I tried posting this in a different section and didnt get a response.



2007 GT, 5spd manual, 3.55, JLTII CAIand Bamachips 93 Race Tune

My car is suddenly pulling timing with a tune that was fine.

Normal - 106.7 mph (for conditions)
Today Full Timing - 105.3 mph
-2 degrees - 106 mph

It did the same thing three weeks ago and I thought I got a bad tank of fuel.
The next week I used a new fueling point and it performed normallly.
This week using the new fuel point performance was off again.

1. Carbon buildup on the pistons or dirty injector causing it to go lean on one cylinder?
Run a dose of Gumout Regane through it?

2. Restrictive fuel filter causing it to lean out?
Change fuel filter? It only has 6000 mi.

3. Just getting unlucky on fuel?

Any other ideas?

 

Have you reloaded the tune? Maybe something went wrong with it...[&:] I don't really know what to tell you I'm not an expert on this stuff

 

We're changing from winter to spring, and some parts of the country use different winter/summer fuel blends with different volatility. Maybe you're getting differeing fuel from week to week as they switch over(if they are doing it right now in your area).

 

Guessing (just because you guys tend to get agressive 93 tunes)... the fuel you are getting might be 93 or it might be an ethonyl mix / crap. I had tons of issues on the old car with detonation running 92, 92.5and 93 ocatane from various places.... 93 BP was the only gas it liked and itwas VERY tough to find.

 

+1 Gene, there are more and more palces here getting the 10% ethanoyl mix, and it jacks stuff up

 

Actually the fuel Ive been having issues with is the BP (Amoco) 93.
I didnt try a different brand just a different station.
I thought it might of gotten adulterated with 87.

If it hadnt been running fine on the same tune for months I might think it was the tune.
TheWinter to Summer fuel idea might bear investigating.

I have a sneaky suspicion its just carbon buildup on the pistons. Ive had sucess with Gumout Regain eliminated detonation after running a dose to clean the chambers. I had a car once that needed a dose every 1500 mi to keep it from pinging.It didnt have a knock sensor so I had to rely on a trained ear.

 

Hmm.. well that ruled out that theory. haha...

Carbon buildup common on the 3v?

 

I dont really know, but if the tune is dead on it wouldnt take much to put it over the edge.
The fact that pulling two degrees of timing seemed to take it out of the knock range makes me think its still pretty close.
I didnt try 1 degree but it may have been enough as well. I was just trying to get a quick read on what was going on.

 

My '05 S197 started pinging last year with 18K on the clock. Tried different brands of 93 octane without any luck. Dumped a can of Seafoam in the tank, and the pinging disappeared after 200 miles. And it has not returned.
Quite a few other S197 owners on this and other forums have also had pinging problems that were solved with a fueladditive(Seafoam, Techtron, etc.). So it appears that the S197 is prone to carbon build up.

 

Thanks Ski!

I had a bright idea today maybe it was ingesting oil from the PCV.
That would cause detonation on its on + carbon build up.
Pulled the air intake to check the TB and Intake Tube for oil....
Dry and clean as new....

My X3 for some reason refuses to download a datalog (livelink shows a initialization fault).
I watched it in realtime during a 3rd gear pull andI have26.5 degrees in the 3800-4600 range (peak cylinder pressure) risingto 30 degrees at 5000+ rpm.I shut the run down at about 5500 rpm. I didnt pull it all the way out as 6800 rpm is 113 mph and it was a public highway. Thats with 196-198F Coolant Temp and 56-60F intake temperature.

Most of the guys that know their timing have been telling me they are running 29-30 so it doesnt seem to be pulling timing now.
Of course I have bought fuel since I had the issue.