4.3l v6 strange miss problems

I have a 2001 chevy s10 with the 4.3l v6, Problems started about 2 months ago. Hot start after 10 minute shut down, engine does a millisecond shut down then drives ok for the rest of the trip. several days later, it throws a p0102 code twice and sets off the SES light. 2nd or third drive it clears itself. but the p0102, 01/01 wont clear, and the strange millisecond stall still occurs randomly. Have been checking various items, like fuel pressure, obdII data, etc. Cleaned MAF, but dropped it, so had to buy a new one. It is reading about 0.6#/min at idle, and as high as 12, when acellerating through gears. Also noted that starts were taking about 3 seconds, normally, they take about 1 second. Had this problem 4 years ago, and solved it with a a new fuel pump. Problem still was occurring. Came to wrong conclusion that the fuel pressure regulator was causing the problem, so replaced it with a midprice new one. First attempt to check it, the fuel pressure dropped from 57 psi to below 40psi in seconds. Didn't like that result so, put fuel pressure gauge on the output of the inline fuel filter to see if the pump check valve was leaking. Result was the pump jumped up to 90psi, bled down to 60 psi, then held between 60 and 40 psi for about 30 minutes. Concluded that the first leak down was not back through the fuel pump. Checked the bleed down at the rail schrader valve again, and the bleed down was a little better but drops from 57 to 30psi in <5 minutes. some where in here checked fuel trims and they were way out of wack, ltft > 24% both banks, stft bouncing around all positive like the closed loop system was trying to feed more fuel to the engine. On next short--3mile test run-- the fuel trims have come down ltft about 10% and stft about 0. But it threw another code P0131 as well as the original P0102 code.

I'm betting that I need to replace the new fuel pressure regulator, since it is about 5 psi low and may be slightly leaking. I'm not sure if the P0131 code is a result of the original problems and "may" go away if I solve the first problems or if it is the main culprit in causing all the issues.

I'm retired now so don't do a lot of driving--120,000 miles on the truck.

Would some one like to make a few recomendations? I have just a OBDII reader, no scope analyzer type equipment.

Regards,

Vic Jordan


I fortgot to add that driving with the OBDII reader, it has forced a reset several times, when this has never happened previously--made me think that some sort of electrical intermittent is happening. Had to replace the radiator about a year ago, since then have added 50/50 mix twice about 2 qts total--haven't checked for a head gasket leak, but don't think that is a problem. Don't see any white smoke or any smoke at all.

 

This is recorded live data, the trigger point was in the middle of the data field. The important part is that the ses light was on, the car was accelerated from stop up to 55 (speed limit) then coated back down to 40 hoping to catch the stumble, but failed to occur.

This is freeze frame data, it only stores certain info not all that is available
George,

here is the spreadsheet data from todays testing. I tried to send you the maf scope pictures I took yesterday, but they must be too big to fit in this forum file size. I don’t know how to compress them.

there is some obscure data in a few spreadsheet fields, but it is accurate to the Inova obdii data as collected.

vic

 

What scan tool did you use to capture the live data?