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chasing studder/stall on cold start

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chasing studder/stall on cold start

Old 12-27-2018, 04:50 PM
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chasing studder/stall on cold start

Hi, I have [color=left=#800000]93 5.7L K L05 with 16168625 pcm and BDJZ code. Stock. In a C1500 suburban.
I've been chasing a studder/stall after cold start. I have recently replaced the fuel pump (bad sending unit, replaced pump while in there - didn't notice difference after), EGR valve, and verified to best I can injectors seem to have good pattern.
I captured log data using TunerPro - thinking maybe I could get idea where/what was causing problem but I've no experience in this. I can see things happening - but nothing obvious to me. Kinda a chicken/egg thing for me, can't tell if what I see is result of the stall or cause of the stall.
Data below is about 1 min after starting on about a 60 deg day. back out of drive, put in drive and at constant throttle it starts ok then studders and often stalls unless I mess with the throttle. I also often have trouble on cold start unless I give it some throttle. Runs reasonably well after warmed up (most of the time..). I looked thru all the data output from Tunerpro and did not see anything changing rapidly at time the stall starts except timing, rpm, etc. - highlighted data. Any education/advice would be appreciated. It's been a while since plugs, wires, rotor - so that was going to be my next step unless someone has experience that can save me the time. [/color]
stall cold start 1.pdf
stall cold start 2.pdf
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stall cold start data.pdf (223.2 KB, 5 views)
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Old 12-28-2018, 04:38 PM
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Re: chasing studder/stall on cold start

I'm sure someone far more intelligent than me will be along soon to help.

Just curious what the coolant temp numbers look like during this cycle. Have you looked at them?
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Old 12-28-2018, 06:48 PM
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Re: chasing studder/stall on cold start

It was a cool start & drive - about 60 deg F when it studdered/almost stalled. Starting temp was about 50deg.
I've read a bit since and it seems knock counts are too high? I also noticed that knock counts sit on a constant 747 counts during period of stall/studder. I've noticed in other runs (while driving OK) that knock counts will also sit on some constant value. I don't know what knock counts should be doing, don't have any experience on TBI data logging - but seems to me that "real knocks" wouldn't be so constant and it may be noise which is being counted instead of actual knock/pinging.
I thought I'd go through grounds, check/clean them and see if that makes any difference. Perhaps false knock counts are causing spark timing retard.
I can't log actual knock retard as ads outputs battery volts unless I change a value in bin - but I can only log data now.
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