update...
Ok. I've had a couple more opportunities to check things and log some data. I believe I have a lot of information to post so I'll give everything in chronological order....
Last Saturday (4/4/09) I had the help of two good friends from our local Buick club. We checked, set and verified the cam sensor - it's 100% dead-on. That same weekend we also did a vacuum system check by pressurizing all the vaccum lines with compressed air and checking for leaks. Almost everything was leak-free except we did find two small leaks in the wastegate plumbing, these were small leaks but we replaced the leaking hoses and re-checked for leaks - no more leaks there. Took it for a test drive and there was no difference, still all the same symptoms as before.
Yesterday afternoon (Friday 4/10/09) I took the car back to my friend's shop and we spent a few hours checking things and logging data. We made some interesting observations, but didn't manage to fix it yet. One of the first things we checked was the crank shaft end-play but it checked out ok, within spec. Crank end-play was within spec. I've given a description of 5 data logs below:
Data log #10 and #11:
- Adjusted the wastegate actuator (lengthened) to what I *expected* to be about 12 lbs. It was previously running up to 15 lbs which is consistant with what I *thought* I set it at. (I've mentioned this because of what we discovered *after* all 5 data runs)
- Put transmission in 2nd to eliminate any possible disturbances the transmission might be inducing
- rolled into throttle somewhat slowly
Data log #12:
- No adjustments made
- Transmission in 2nd
- Stabbed throttle instead of rolling into throttle
Data log #13 and #14:
- Same conditions as data log #12
- data gets interesting this time!
So based on those five runs, it looks like I have 3 pretty clean runs and then things went haywire with no changes made. However, to me it looks like the last two runs point to a bad crank signal as was suggested previously.
Now, here's where things got really weird...
We wanted to see if the issue had anything at all to do with boost so we disconnected the wastegate actuator and took it for a test drive. Much to our surprise, the car still made 15 lbs. of boost!!! We figured the wastegate must have been binding up or something so we wired it open with a piece of steel wire. Nope, the wastegate wasn't binding - even with the wastegate wired *completely* open the car will *still* builds 15 lbs. of boost!!!
It does take it a while to get there, but it does hit 15 lbs everytime. So, I believe it's logical to deduce the wastegate port is too small. I have not removed the downpipe to measure the port size, but I'm hoping to have a chance to do that this evening. The downpipe is an ATR 3". I purchased the turbo from another board member (don't remmeber who) and it's *supposed* to be a Limit TE-44.
I didn't log any data with the wastegate wired open because my laptop battery was dead by the time we discovered the boost issue. But, with the wastegate wired open and the boost coming on slowly, the popping/misfire seems to be *gone*! I don't know how that's possible if there is an issue with the crank signal.
So, thoughts???......