Bad injector-chasing my tail

[ThikStik]

This car, in sig, has always had hi o2's and K. Turn fp down just get more K, and alittle lower o2's. Just when i think ive got K down to 4 or so, I go wot another time only to get 8-20!K Its horrible , with the engine stumbling all over itself. One good punch, and 40 miles later, one horrible punch -on same gas!

Im suspecting that ONE inj is bad. Here is why: I hear only a single knock, not like other cylinders are doing it. I have fp bleed down after car off over 5 minutes. Last rebuild showed a couple of cyl had run way rich-but there was a small crack in manifold. On this rebuild with newly welded manifold, I can hear small tick from exhaust, but dont believe it could throw tuning off this badly. The inconsistancy is unreal.....does this sound like ONE injector could be flaky?
Any help is ...help.
Thanks

 

[LV GN]

check the injector wiring harness for shorts due to rubbing and the rubber hose that hooks the fuel pump to the hanger..

 

[Razor]

You need to make sure that the numbers on your scantool are normal first. You havent listed numbers like BLM, IAC, TPS, MAF, etc. The BLM and MAF are the two that show fueling. Issues primarily with those two will always have consequences.

Your fuel pressure bleeding down is either injector, fuel pressure reg, or fuel pump/area issue. Injector will typically show up on one cylinder. Use a stethescope and listen to them individually..that sometimes works. But if its an injector..your BLM will be skewed big time.

Bottom line.. you need to use a scantool and learn to read its numbers.. as it tells you what the ecm is seeing..from there you make your decisions. Decisions without DATA are always bad ones.

Drop the boost on the motor before you hurt sumthen :wink:

 

[bruce]

Im suspecting that ONE inj is bad.

I had what I thought was a bad injector, for a couple days, and then it mysteriously cured itself. 2 days later, driving at 35 MPH, a corner of a piston literary fell off #3.

If you have any doubts about an injector being iffy, get then out and cleaned. Better yet use it as an excuse to update to bigger ones.

 

[ThikStik]

Thanks for the great info guys. Well, I did find that the oil pressure/fuel pump bypass 3 prong harness was rubbing (down to brass on terminals) against damper. I have it dangling due to using a mech oil press tube. This hopefully, is why I got that transient horrible double digit K yesterday. Maybe hi rpms were sucking it onto the damper and grounding out fp. Theres no doubt it was touching at times. Ill drive it today , and scan.
Past scanning shows maf-255, tps -4.5, blm-128, iac-dont know. But do know that my throttle body has gobs of play. I replaced its seals, but the idle still hunts, and there is a free running miss (unloaded).
I have checked the fp at wot and its around 55.
So, do you guys think 1 inj cause hi o2's? Bruce, was your inj lean on that piston?

Thanks

 

[ThikStik]

Update: I got oil press harness out of the way. 4 wot runs were good , only 2 degrees of K. So I figured it was fixed (how naive) and tried a pull from a 5mph dig. Well it crapped all over itself with double digit K. I wish I had those scans.
Another hiway scan showed K=5, blm=138, o2=845, maf=140 at 4800 rpm.....thats the one that may tell the story, or maybe the maf flow was redusced as timing was getting pulled. This is using a slow Auto Xray scanner, its numbers are good, just slow.
I need to give up on these injectors and maf, thats all thats left that hasnt been addressed on this POS machine. I have fixed so much on this POS like a leaking intercooler, plenum gasket, cracked manifolds, corroded ecm contacts etc, but nothing ever solves this cars problems. I just got the K down to 3 or so, and now it is transiently into the 20's....SWEET.