I've read thru a decent amount of material on thirdgen.org, and found that you guys are generally pretty decent folks. I've also done my footwork as a newbie, and searched trying to find something that looks like my problem. No such luck. Some were close, but nothing is right on. So lets start... this might get to be a long one...

I've got a 454 which has an EFI kit installed on it from customefis.com. John has been very understanding thru my whole ordeal, so thanks to him in case he gets out here and reads this! Since I've installed the kit, with all new sensors, filters, good matched injectors, etc, etc. the system has been lacking in the low RPM range. Meaning, I can crawl away from a stand still without much problem, but if the engine is loaded up quickly, it tends to stumble and sometimes even backfires (thru the TBI I am pretty sure)!

Timing is the first thing I looked at. Its set at 6* right now, and I went thru min idle speed adjustments and reset the ECM as I have been instructed.

The system runs in closed loop. No codes are thrown at all.

I have a VSS.

I don't use a knock sensor... as I was told this is an optional item, that I don't really need. I guess some section of the chips programming can be removed for it to disregard missing knock sensors???

I've got HEAVY cooling on this engine, but it does get up to temp just fine, and rides along between 175-210*, which is pretty good for a BBC - again thats what I have been told.

I've run WINALDL against the motor, but nothing for long sustained runs... one thing I do notice is REAL freaky O2 readings. I've got .004 - .955. I've noticed that the readings tend to drop when I begin to accelerate, no matter how hard I hit the pedal. See the BLM file I have here:

http://12.208.69.79/images/truck/mis...154558_LOG.xls

What else... I am just trying to be as thorough as possible to eliminate questions...

AH... one thing that I have having a HORRIBLE time with. The headers I am using are leaking some. I can hear the ticking when it starts up, but once it warms up slightly, most of the ticking calms down almost completely. Customefis.com tells me that even the smallest exhaust leak can trash your O2 sensor reading, and thus throw off your A/F ratio. Is this correct?

I think thats it. Thanks to all that will help out a newbie on his first time out. I hope I've done enuf explaining to show that I've done my homework!

-Dan

 

Yes and exhaust leak can cause problems with the O2 sensor.

You may be causing a small amount of air to be sucked into the exhaust flow, or it maybe pushing it out. Either way will tell the O2 sensor you're running rich, or lean.

Another possibilty is a vacuum leak. Those cause HUGE stumbles. Pretty annoying actually.

Try snugging up the header bolts, and pull the air cleaner to check all the vacuum hoses. Another trick is to spray carb cleaner around the base of the TB. If the engine revs higher, you've got a leak there.

 

Vacuum leak huh... like a leaky intake gasket for example? I think I may have a minor leak on my passenger side intake gasket... would that make for a real problem?

-Dan

 

I finally got new exhaust gaskets installed. I used Mr. Gasket "Ultra Seal" gaskets. They are metal reinforced, not just heavy paper. I also used "Ultra Copper" RTV on the gaskets. This seems to have fixed the BLM and INT readings from bouncing all over. Now I am off to burn a new chip, seeing as the O2 is reporting a VERY lean idle condition. I'll post how this works for me very soon.

-Dan