Swamper104

Here's my situation. When my truck gets to about 65 mph on the interstate it starts to surge and buck, like a rev limiter is kicking in. I've heard that their is a park/neutral rev limiter that kicks on around 3000rpm or so on the automatic vettes.
The VSS is currently not working on my truck, I think due to the sending unit on my T-case. So the PCM is never reading any speed. Could this rev limiter (if it exist) be causing this by shutting down my injectors?

John B

iTrader: (10)

Have you ATAP'd the vehicle?

Swamper104

No John, I haven't. I would be willing to buy one and try if neccesary. I have put a Snap-ON scanner to it and it and the only codes it showed were for the VSS and some type of traction control code.

Speartech

iTrader: (14)

Yes! There is what's called a "Bad VSS" rev limiter. If you drive with your scanner on when the condition happens, you can tell if that's it because the imjector on-times will go to zero if it's a rev limiter kicking in.
Providing a VSS signal is important to the computer, even if it's very inaccurate. The computer really needs to know when the vehicle is in motion.

Swamper104

John, ok this may explain things. You did my programming and harness for me (it's been about 7 months ago). Until know, the rev limiter thought had not hit me, I thought it was a fuel volume problem. I had to cut the vette VSS connecter off the harness because it would not fit the connector on my Transfer-case. I spliced the wires into the original ones from the t-case connector but I guess something didn't work. Is there someway I can fool the PCM into thinking the vehicle is in motion or do I have to find a way to hook that up? I was planning just changing to a mechanical speedometer. Thanks.

--Davey Jordan

Speartech

iTrader: (14)

You don't HAVE to find a way to hook it up, but it would sure be nice to feed a speed signal to the computer.

I think the main thing is to be sure this is your problem. You need to make a run up the road with scanner in hand and fuel pressure gauge taped to the windshield.

Monitoring rpm, injector pulse width, fuel trims, and fuel pressure should pin down the problem.

If it's the rev limiter, the number can be raised, and the VSS code shut off.

Swamper104

Ok thanks. I will have to wait I can get till back to the shop and use the scanner. Unless someone wants to volunteer a scanner in the Nashville area :-) I'll let you know what happens.

--Davey Jordan

Swamper104

IT'S FIXED!! This is such a major relief. I can't describe how good the truck runs. I've forgotten what it was like to drive over 60 and I've sure never done it with a LS1. All I did was take the 2 VSS wires coming out of the PCM and grounded them. That's it, toke all of 1 minute and I've been fighting this for six months! If there is still a rev limiter there I sure haven't reached it yet
Now all I have to do is put in my mechanical gauges and I'll be good to go. There's nothing like the feeling of pulling on to the interstate grabbin third gear and hearing the tires break loose (Remember, in a 3/4ton 4wd with 33's). Well I really can't describe how good a day this has been.

--Davey