I'm new to these 4.3's so I'm not sure how much pick up and go they're supposed to have...but I feel like they should perform a lot better than mine currently is. Feels somewhat sluggish when taking off, like I have to give it a lot of gas in order to go anywhere. 98 Jimmy 4x4

Here's what I've done:
Spark plugs (AC Delco iridiums)
Wires
Fuel filter
Techron treatment x 2
Air filter
Cleaned MAF sensor
PCV valve
Verified condition of all vacuum connections
ECT sensor
No codes present

Tomorrow, I will be replacing the cap and rotor with AC Delco parts. I'm not sure how old the current equipment is. Is there anything else I should be looking at? Seems like my engine has a slight stumble or hesitation at idle, too.

 

Did you think of checking compression? Did you clean the TB. What did the plugs look like?

 

No I didn't think to clean the TB or check compression. Might get one of those Seafoam intake cleaners today and try that, too.

http://4.bp.blogspot.com/_mwzxyywxcG...plugs+sign.jpg

Spark plugs that came out were Denso TT's and were "normal" -- slight brownish color.

 

So you cleaned the MAF, but have you tried driving it {warmed up} with the MAF disconnected?
Difference driving cold and hot?
Any starting problems?

 

If you don't have a compression tester would'nt worry most likely not the problem. I think your going to see big improvment with cap and rotor. If Pettys MAF trick does not work start looking at fuel pressure, that is a gage thats a must have.

 

Cap and rotor replaced with AC Delco parts...the terminals on the old cap were very white. Rotor has seen better days, too. Didn't really notice a change.

I had the truck warmed up and as soon as I unplugged the MAF sensor it died. No stuttering, no hesitation...just shut off.

Cold and warm, it seems like it runs the same. I haven't noticed any starting issues although if I shut it off and then have to start it again within 10-15 seconds it starts VERY fast...don't think that's really a problem, though.

Edit: do I have to unplug the MAF BEFORE I start the vehicle and run it? I thought I read some other threads that mentioned people unplugging it while it was running so that's what I did.

 

Unplug MAF with key off so that the PCM notices it gone on self test and will then select different mapping.

If it still doesnt want to keep running, you've established that there's something wrong other than MAF.

 

I will go unplug MAF with key off and run it for a bit and edit/report back with my findings. I would rather replace a ~$100 MAF than replace the spider or something else fuel related.

Edit: unplugged MAF and let it warm up. Truck runs very similar with MAF unplugged. There might have been a SLIGHT increase in acceleration/pick-up, but the slight stumbling at idle is still present when not plugged in.

 

Should this point me in the direction of a faulty MAF sensor? None of the parts stores are stocking a fuel pressure tester for rental, so it might be a few days until I get to that point.

 

USUALLY...
If the truck runs same or worse unplugged, it is NOT the MAF.
Runs noticeably better it IS the MAF