Poor Performance at WOT with Quadrajet

[b4black]

Poor Performance at WOT with 4.1L V-6

I found this in an Oldsmobile training manual:

A poor performance comment may be received from a customer......on 4.1 V-6 enigines....It may be described as running out of fuel when actually the engine is running too rich.

This is very interesing. I believe I was experiencing this last time I raced. I ASSumed that too rich would result in black smoke. The car was dieing at about 11 psi of boost. When I went to richer rods, it happened earleir.

So, too lean = knock
too rich = WOT stumble/die.

 

[Ttype83]

What rods are you using????

Before I got my vac leak I was having this problem over 10-11 psi boost. I was/am using CS rods w/K hanger.

 

[GNVAIR]

Rich,
Have you tried tuning it with an EGT or a wide band. Either of those items would probably work perfect on a carbed car. You said in a previous post that you have an OTC 2000. That is an excellent scan tool. What are the O2 voltages like at WOT?

 

[b4black]

With the stock R hanger and CP rods, if stumbles at about 11-12 psi. With F-DS, it happens more like 8-9 psi. I also have bent the tab back that lets the secondies air horn open further. I not sure what effect this has.


Lee, I never paid attention to the O2 counts. I'm the only one here with a scan tool, so I have nobody to compare to. I do know the display always reads "rich" when at WOT. I purposely was running as rich as possible to rule out a lean condition causing my shift knock. I've found out that even while running rich, with high octane fuel (xylene) and cold air (K&N cone) it still knocks. So I pretty confident it's false knock.

I thought maybe my stumbling at high boost was cuased by the timing being reatrded, but now I believe it was simply because I was running the carb so rich.

 

[Ttype83]

Originally posted by b4black
I also have bent the tab back that lets the secondies air horn open further. I not sure what effect this has.
I did the same thing


Lee, I never paid attention to the O2 counts. I'm the only one here with a scan tool, so I have nobody to compare to.

I've asked santa for one, But I do know some one else on this fourm that has one.... I think that she won the bid on Ebay....ummmm

 

[Tonya83T]

Originally posted by Ttype83
I think that she won the bid on Ebay....ummmm

Uhhhh, if you're speaking of me......I could never get the damn thing to work. When I plugged it in (it's been a long time since I've even tried) it would preform it's self test & say "systems ok". but then I couldn't select any functions. I just gave up after a while. I have thought about trying to send it to the company it came from to see what the problem was or be rebuilt, but ya know............I'm a procrastinator & I'm lazy.
Turbo-Rich is always on my case about it, but I'm a hard head.

 

[GNVAIR]

The OTC 2000 will show O2 voltages. The same rule of thumb that applies to the newer fuel injected cars applies to yours. O2's higher than 850 mv's is pretty darn rich. Actually, I think it will be 950mv's as the Snap On and OTC scantools read 100mv's higher. Regardless, I would get some 02 readings and try to get an EGT. Gradually try to lean it out once you have a starting point.

 

[bill]

Any body interested in a monitor 2000? don't need it anymore bcause i have a mon. 4000E and an OBD II scanner also.let me know.

 

[Turbo-Rich]

Might be.
Whats ya askin'

 

[bill]

I would say $150 plus shipping.it's also got cartridges for ford and hook up for crysler.I think the ford cable is missing,I will have to look it's been awhile since I used it.but the GM cartridge 81-86 is there and the cable to.I'll pull it out and test it to make sure it still works but i don't see why it wouldn't.If nobody want's it maybe I'll try E-BAY.

 

[Turbo-Rich]

Not a bad price Bill but $$'s kinda tight right now w/the garage & kid on the way. If no one here wants it I'm sure someone on e-bay will
Thanx anyway.

 

[b4black]

This "high boost stumble" seems to be becoming a fairly common problem. I just got a letter from TurboTony (who is without a computer at the moment):

....if I keep my foot into it, I can get to 12-13 psi range, but the car starts to surge pretty bad. Could this be from fuel starvation? Maybe I should go with an electric fuel pump?

I was thinking the same thing until I read that passage above. The remedy from GM was to go to leaner secondary rods. Junkyards are loaded with "DD" rods, which a pretty lean. If you've haven't ever changed secondary rods, don't worry, it is about the easiest thing to do. Just remove the screw between the too large butterflies (air horn) and pull up on the hanger.