1998 Vortec timing and fuel issues

[KAZ MotorSports]

I am having a beast of a time with a 1998 Vortec that has been BUILT, stroked to 383, and has a Whipple strapped to it.

We dropped the compression to 8.9:1 and at this air density it is running 5.5 psi_g of boost.

This some o' the bitch is giving me fits. No matter what timing I put to it at idle it will not go above 16-18* of timing. My cell tracing is working (THANK YOU BLACKY!) and I am putting in the values all around the traced cell to try and force it. No-Go. I know she wants around 22 or 28 to idle smooth and this is burning me up. Once the throttle is open and up in the RPMs the desired timing is present both on the log and manually looking at it with a timing light.

Also I am seeing something I have never seen before and hoped someone has experienced this and can point me in the right direction. My LTFT are showing Bank1 at -5.3-ish, but Bank2 is showing -14.3-ish. My 02 sensors are showing a great response and sweep...but this is troubling me. As far as the customer knows the 02s were done about 15k miles ago so they should be fine. The exhaust is solid and no leaks.

Any help will be greatly appreciated,
-Kenny

[N0DIH]

Got any datalogs to post? That might help.

Any fuel leaks like FPR leaking? I wrestled with a -18.0% LTFT on my 454 and it ultimately was the FPR leaking. Passed vacuum pump testing, but at the high 4 bar fuel pressures the 96-00 Vortec Gen I V8's have, it leaked, but under the -0.8 bar vacuum pump, no leak was detected.

Anytime you are boosted you SHOULD be in PE Mode.

[KAZ MotorSports]

I do not know if the FPR is leaking honestly. The customer installed a Walbro 255/Lph HP pump in line. He removed the factory pump from the tank and installed the Walbro. Think it is over pressurizing the factory FPR?

How should I diagnose the FPR leaking? Do I have to remove the Vortec bonnet (top cover)?

[joecar]

One thing to try would be to physically swap the O2 sensors between the banks, and see if those LTFT's follow the sensors or not.

[KAZ MotorSports]

joecar,

I was thinking about that...but after a 14 hour day today I could not bring myself to crawling under the truck. :bawl:

I will give it a try tomorrow morning.

Good-night,
-Kenny

[N0DIH]

Do I ever know that feeling!

Check fuel pressure, going that much is easy by over pressurizing too.

[97K15004WD]

joecar,

I was thinking about that...but after a 14 hour day today I could not bring myself to crawling under the truck. :bawl:

I will give it a try tomorrow morning.

Good-night,
-Kenny

Any results?

[KAZ MotorSports]

I will find out tomorrow. I had to cut the stock pipe to remove the section of pipe with the 02 sensor in it. Severe heat and plenty of penetrating fluid and she would not budge in the truck. Got to love the frikkin morons who can not take 4 seconds to dab on a touch of anti-sieze. :bash:

When it did finally come out...all of the vains but two were covered over in additive spatter. Need to weld the pipe back in place in the morning with the NEW 02 sensor in it to see what is up.

[KAZ MotorSports]

With the new 411 PCM in place the trims are equal on both sides. Injector driver in the Vortec PCM?

[98 tigershark]

4 bar should be 58 -62 psi w/ 40lb hr injectors. do you have a wide band sensor and and adjustable fuel regulator? On my 98 vette my AFR is right on and so is the psi but my LTFT average is what I use and they are -.8 bank one and 0 on bank 2. my short term is 3.2 bank one and 1.6 bank 2 and average 3.2 and 1,6 to -1.6 to -3.6. GMPP says this is OK. The 98 pcm is hard as the PROM is different than 99-02 pcms. Just so my afr is good and HP and trq and fuel rail psi are as advertised I wouldnt be to upset. It could even be VE and spark. B00sted and high performance are apps are kind of different on a 98. Check and see if P1336 is off on most 98 I have found this is disabled and enable P1336 and see if it needs a crank relearn. If so follow the relearn and try again. Food for thought :cheers:
98 tigershark