Bad miss at slight throttle, DS file to look at

[BM Computer Src]

I just finished putting a new drivers side head gasket on. The car idles perfectly, with no audible missing at all. There is no contamination of the oil with water. However- it will somtimes stumble slightly when revved up in park but not bad. But when put into drive and power braked or driven, anything more than idle throttle causes a bad bucking / missing. I have recorded these misses on directscan and it shows that the O2's are dropping out to almost 0 when the missing and bucking happens. This means that there is a lack of fuel causing the miss. Tonight I tried changing the O2 sensor out with a new one, but that had no effect. I have verified fuel pressure is not dropping with a gauge. The only thing that I could think of are the grounds by the passenger side head. They are not perfect, but I have grounded them as best I can, and I dont think they are part of the problem but this looks to me like a electrical gremlin. Please look at the DS file and give any suggestions you may have. It is the bottom most one listed under category 5 and I have it listed in bold print.

www.bmcomputersource.com/dscollection.html

Thanks,
Bob

 

[bruce]

Try a known good MAF.
Looks like something is almost loose, with the way the SA chatters so violently.

Slowly tipping in like that will show lean to some degree since there is so little load, and no AE.

 

[BM Computer Src]

I just confirmed it is not the coil pack; I did a swap with a known good one. I will check with a good MAF as soon as I get a chance.
Your right though bruce, a lot of the readings are goofy, like on Crack! (spark advance, O2, etc...)

Any other ideas?

Thanks,
Bob

 

[turbo buicks]

Bob, do you need that MAF back again?

 

[Lee Thompson]

miss

Try this!!
Look at the ground wires on the back of the head. The small tan one is the ground wire for the o2 sensor. Make a new wire ( leave the old one in) Ground it to one of the intake bolts, run it to the ecm and piggyback on to the old wire just before the plug.
I have heard there are some solder joints inside the wire loom that some times break down. Good Luck.
See if this stops your O2/s from dropping to O

 

[BM Computer Src]

Thanks for the good ideas guys. I'll work on it tonight and let you know how it turns out.

Corey, please mail the MAF to me, I'll email you the address.

Thanks!
Bob

 

[BoostKillsStres]

Bob,
By the way, its much easier to get to the 2 ground bolts on the back of the head if you undu the rear trans mount and jack up some as this increases the area between the engine and firewall. The bolts are either 13 or 15mm if I remember. Make sure and pull the coil pack out to help get back there.

I took both connections loose from the head and made my own 10 gauge wire w/ a big ilet on the ground end and simply bolted the entire group of wires together with a nut and bolt through all the ilets, taped the connection up, then ran the wire all the way to the front fender ground for the battery. Not going to have a problem with those again

HTH

 

[BM Computer Src]

It was not the MAF. I replaced with a good one today.

I am cleaning up the grounds but have not finished yet. I also saw 3 spade lugs (locking type) on some ECM wires. I noticed that when I was out testing, I moved the ECM around, and the knock detector went off twice. Sounds like another possiblility.

eeeeeeeeekkkkkkkk..............

It still smokes though, thats odd... I would have thought it would have stopped smoking by now, having burned off all the contaminants in the combustion chamber. Its whitish/blue. Its not burning water, the level has not dropped since I redid the gasket.

 

[BM Computer Src]

ttt

 

[BM Computer Src]

Problem Found!

Cam Sensor.

It was 1/2 turn out.

Car runs great now! I should have known...

A few months back it worked its-self out of whack to the point where the car would not start, and it had been running well for months. (not physically moving) but something internally must be flakey.

Still has the high RPM (4800+) spike of detonation, up to 25 deg, on 15 psi and 18 degrees / pump gas. I suspect this cam sensor is whacked out and will test with a known good one soon.

Im getting there!

 

[turbo buicks]

cam sensor, hmmm. wasnt that what i suggested yesterday, Bob?

next time i come over i can go for a ride again right?

 

[Razor]

Ya Bob..ya shoulda listened to the human direct scan Cory

 

[turbo buicks]

 

[BM Computer Src]

Yeah, I'm getting old!!