Hope someone reads this (long)

[TexasT]

Are you running a catalytic converter? Dumping fuel into one causes it to clog up. It sounds like you are getting a bunch of fuel if you are using the stock settings and the larger injectors.

 

[RKHiPerformance]

Are you running a catalytic converter? Dumping fuel into one causes it to clog up. It sounds like you are getting a bunch of fuel if you are using the stock settings and the larger injectors.

My thoughts exactly...a clogged or failing catalytic converter could cause these symptoms. Even a clog in the exhaust system that was created while the car was in storage could be a possible explanation.

 

[chadly]

no cat

I know my sig does say cat back exhaust, but that’s not really all the way true. I did remove the cat. However maybe the muffler is plugged? I do have a dump plate down where the cat used to be. I can take it for a drive not capped and see what happens. It will be a day or two before I can try this, but thanks I really do appreciate all inputs.

Chad

 

[chadly]

open exhaust

I got home a little early tonight so i went for a quick drive with open exhasut. The car still stalls on top. Thanks again.
Chad

 

[BRAD_PADGETT]

Chadly- What is your BLM warmed up in park? It should be around 128. Otherwise you have vacuum leaks, exhaust leaks before the o2 sensor or fueling is wrong. Lets check this next. Brad

 

[chadly]

blm's 105

Thanks for jumping in and adding knowledge to this puzzle. I checked the blm's and they are constant 105 in park at idle. They stay at 105-108 while driving constant speeds and go up to 128-133 under load.

I know it's running very rich on bottom, becasue it blows a quick cloud black smoke if you juice it off the line. It also stumble at this time.

What do you recomend I check next?

Again thanks for the help I really appreciate it.

Chad

 

[neat]

I'm still not convinced it's not running out of fuel. Your car is acting a lot like mine did when my fuel pump was going out. Lots of power down low, stall out at the top of first (without knocking), then more power after the shift.

Does your car stall out at the top of second as well as first?

In my case, a new fuel pump solved the problem. Since you have done that already, I suspect a clogged/kinked supply line. The clog/kink might be allowing enough fuel by to let the engine run normally until the fuel demands are the greatest, high RPM and high boost. Then, you run out of fuel, the car falls off, it shifts, the RPMs come down, fuel demand lessens, and the engine starts to produce power again. When my fuel pump was failing, it would go crazy lean at the top of first, but only for a second right before it shifted. It never did knock, but I think that's because the fuel starvation was only for an instant right before the shift and the engine was able to deal with it without detonating/knocking. I wonder if you are experiencing the same thing?

Do you have any way to monitor the air/fuel ratio other than the stock O2 sensor? If you run out of other ideas, you might look into taking it to a shop with a dyno and a wideband air/fuel ratio device. If you can get the car to mess up on the dyno, it should be pretty easy to trouble shoot at that point.

There's a dyno where I work, and being able to watch air/fuel, timing, and just about anything else; all while in a controlled environment, while under WOT, with all the diagnostic tools near by is pretty much the ultimate in trouble shooting. The only hitch is when the car/engine won't duplicate the problems on the dyno. Hopefully, yours will mess up on the dyno and a competent trouble shooter (or you, if the shop will let you dink with the car while it's on their dyno) can find the problem.

Good luck, and let us know what it ends up being.

 

[BRAD_PADGETT]

Chadly- Get a can of carb cleaner and spray all vacuum lines and the exhaust headers prior to the o2 sensor while the car is running. Listen for any change in rpm and you have found your leak. If not you have ruled out any leaks. Brad.

 

[Fuelie600]

Chad, I believe your off idle and WOT issues are seperate. You don't mention whether your IAC idle counts are in gear or P/N. I would shoot for 10-15 in P/N, and 30-35 in gear. Raise your TPS WOT to over 4.50 but less than 4.80. Also, take your car for a ride and let me know @ what RPM your motor goes flat. Brian

I still believe you are chasing 2 completely different problems. Your top end lay down is starvation of air ( lack of valve flow, or intake retriction ) or fuel ( lack of pump delivery or line restriction ). You need to monitor your air/fuel ratio to determine this. Your off throttle hesitation might be dertermined by quickly raising your FP ( a couple of turns ) and then immediately blurping the throttle to see whether your problem gets worst or better. You must blurp the throttle within a few seconds after moving your FP to avoid the ECM from compensating. Post back, Brian

 

[chadly]

I can’t say thanks enough

I feel like were making progress and really appreciate all your help and knowledge. I believe I answered all your questions and did a little additional testing as well.

Yes, the car does stall out at the top of second gear. Glad you asked this question as I can now confirm the transmission is not the issue.

I purchased a can of carburetor cleaner and almost emptied the whole can spraying anything that looked like an exhaust or vacuum lines. I can’t confirm for sure that I hit every possible spot, but I did the best I could. No increase in rpm’s. I did spray a shot at the air cleaner just to make sure the rpm’s did increase and they did.

I watched the 02’s as the car fell on its face and they were anywhere from 790 to 800.

I turned the fuel pressure up and down and quickly blurped the throttle, but it was hard to tell which way was better.

Brian I do believe you are correct that there are two issues happening here.

Just for fun I went for a drive and every mile or so I turned down the fuel pressure. My final fuel pressure was at 31 psi. At this pressure my blm’s were still 105 at idle in park and went as high as 133 under load(no change from 43 psi). I recorded 02’s as low as 730 @ 89 mph and 2.8 retard @ 77 mph which I think was at a shift point. At this setting of 31 psi the black cloud that jumps out my exhaust was gone and the stumble if any were still there was not very noticeable. However, the top end still falls flat.

Summary:
Blm’s are way too low.
Adjusting fuel pressure to 31 psi helps if not eliminates off idle to wot stumble.
Top of rpms appear to get enough fuel but fail to make power as if the cam is not enough.

Thanks again for hanging in there with me.
Chad

 

[Fuelie600]

Chad, it seems you need to get with your chip maker and have him take some fuel out of your off idle program. This is refered by some as the "accellerator pump" mode, although we all know that's a carb term. Make sure he understands what injectors you are using and ask his recommendations on fuel pressure.

Try to get a WBO2 and monitor your WOT A/F ratio so we can sort out your top end issue. The factory type narrowband is simply not accurate enough and the stock ECM's log rate is waaaaaaay to slow. You could be experiencing a good amount of detonation between frames, and never know it.