Here's My Problem

Low RPMs, high load, lots of knock, and a stumble. When I get on the gas at low rpms I'll get around 4 degrees of knock. My spark advance will drop down to around 10 degrees and the car will stumble. When it stumbles the knock retard will go back and fourth from 4 to 12. I only use 93 octane and it doesn't matter what temp the car is.

Pretty much everything has been replaced (wires, opti, coil, fuel injectors, plugs, you name it, its been replaced.) Everything looks ok on the scanner, except at idle the long term BLMs on the passenger side are around 117. Once you hit the throttle they both get pretty close to 128.

 

I had a stumble under 2k when i would get on the car too fast from a stop. The motor would hesitate/sputter/stumble and then when it reached ~2K it would kick in light up the tires and take off like normal. It would even backfire at times. I changed everything, and the solution turned out to be my fuel pump. I changed out the TPI pump I had running the motor with a Walbro 255 lph, and the thing is more reponsive than ever! Night and day difference, Walbro 255lph

 

First question, what is high load at low RPM's mean? You got the car tied to a tree? Or are you taking off in 2nd gear?

Second, have you ever checked the fuel pressure? Is the vac line to the fuel pressure regulator wet indicating the diaphragm has a hole in it? what is the fuel pressure when the problem occurs? Gages are cheap and easy to tape to the windshield when you want to test the FP.

Do we assume you replaced the TPS and you didn't mention what year you have so we don't know if you have a MAF or not.

After the problem occurs, what indication does the plugs give you? Does it look like a rich or lean condition?

Have you looked at the EGR valve? What happens when you remove and plug the vac line to the EGR?

Remember, vacuum is highest just off idle. Have you checked for vacuum leaks? Use a vacuum gage to see what the level is when the problem occurs.

 

Thanks for the replys guys

High load low rpm = 6th gear 55 mph and full throttle. I've checked fuel pressure around 36 at idle with regulator on and 42 without. I also taped it to the cowl and it looked ok. Anyways when I floor it, the O2s are around 900 so I think I'm gettting enough fuel. TPS is fine, no dead spots or anything in it. I've swaped MAFs before. Plugs look fine. I've tried 3 different sets. EGR is Blocked. Vaccum is fine. I also replaced the intake maniflod gasket just to make sure.

Also, The knock retard is alot more sensitive when it is humid out.

 

Sorry, I'm gonna have to TTT

 

The intake elbow (after the MAF) is sealed tightly against the TB and not letting fugitive air in? Triple check this as it might explain your split BLMs.

The injectors are seated properly and electrical connections are solid?

RK-Sport headers and Taylor wires make me question if you've burned a wire. Been there done that (several times) - #6 and #8 are the worst.

Are you still running a stock program?

 

Ya the MAF is sealed up pretty good. Its a vortech so it makes a good seal. I've burnt a few wires before but all of them are good now. I have actually tried 4 different sets of wires believe it or not. The only thing I've done to the computer is make the max retard 4 degrees but for some reason I still get 12 degrees sometimes.