I finally got my '07 5.3 Vortec fired up in my '66 Jeepster. It sounds great at idle, but as soon as you hit the gas, it revs up, then cuts the fuel. It doesn't stall, just drops the rpm down, then fires off again and does the same cycle over and over as long as you hold the gas pedal. As soon as I let off the gas, it drops back into a perfect idle.

It seems like a programming issue. I don't have any fault codes and the MIL is off. All of the basic parameters check out okay with the scan tool. The motor is from a flex-fuel Siverado Classic which may have something to do with it. The auto was replaced for a manual trans and I reflashed the PCM accordingly. I don't believe this one had a separate Fuel Composition Sensor, but have not been able to confirm this.

Any ideas on what to check?

 

the '07 didn't have a seperate fuel sensor like the L59 ( until '06) Yours should be a LMG or a LC9. Those had a virtual fuel sensor which means the ECU software managed the diffferent fuels according the O2 sensors. What pops up in my mind is the active fuel management both engines had. As far as I know the wiring is more complicated and the instrument cluster was part of the engine's wiring..... How did you manage the ETC ( drive by wire..)

I will do the same swap into my '99 Tahoe in a few months....

 

Thanks for confirming there's no fuel composition sensor. I thought that was the case, but wasn't sure. I did delete the rear O2 sensors. I wouldn't think that would create a problem, but. . . .

I don't think the wiring is much different from the earlier versions - at least on the Siverado Classic. ETC was simple -- there's a separate controller wired into the pedal and the throttle. Its pretty much plug and play. That gives a position signal to the PCM. I've confirmed that the pedal is working (can see the throttle move) and the scan tool accurately shows the % throttle. The rest of it is pretty straightforward. There's a serial data line to the gauge cluster, but that's it. I'm not using that and basically modified the harness for standalone.

 

What is your fuel pressure and is it steady during the revs? What are your MAF and MAP values during the scan?

 

Fuel pressure is 60 psi and doesn't seem to fluctuate with the revs. I'll need to check the MAF and MAP -- I don't want to **** the neighbors off anymore tonight with open headers. What am I looking for? I assume MAF value should increase when the throttle is cracked open and MAP should decrease. I'll try to log it and get a max and min value. Thanks for the help.

 

More info -- MAP seems fine, but I think the MAF isn't right. Its at 1 lb/min at idle and never goes above 2 lb/min. This seems low to me, but I don't know what the upper values should be. If I open the throttle slowly I can get it to keep running up to about 2k rpm, then it drops off. The MAF values don't seem to correspond with the throttle opening after the initial jump to 2 lb/min right off of idle. I checked the wiring and it is all fine. I'm starting to think the MAF is bad -- I know it took a trip from the fender to the garage floor a while back, but I didn't think twice about it. Anyone have any thoughts on this before I drop $$$ on a new MAF. And, if I need to do that, is stock the way to go, or Granatelli or ???

 

How does it run when you unplug the MAF?????

Mike

 

What he said