update on LT1 cold start/idle issue

[BLK95TA]

so you might remember my post a week or 2 ago about how sometimes my car will run for a half second and then die on initial startup and then run fine on restart.

i had also mentioned sometimes it would start up but idle rough. well i caught that on video today and something suprising as well.

normally when this happens i will shut the car off and restart it to clear the problem however today i was filming and was letting the car run. after approx 45 seconds the car actually started running normally. you can hear it on the video. weird to say the least.

does this mean it's more likely something like an IAC problem than the fuel pump/FPR i was originally suspecting?


http://www.youtube.com/watch?v=EQIHqaMyENg

[quik95lt1]

sounds like it had like 0* of timing in it then it woke up

[96LT1355Z28]

Quick95, I'm not good with the PCM stuff but is it possible it's something with the tune from open vs. closed loop? Seems like somethings not right till it starts running off of O2 data in closed loop.

I guess the OP could get a scan tool and watch the O2 data and see if it changes when the car goes into closed loop.

[BLK95TA]

fwiw this motor is essentially bone stock. there is no tune in the pcm and nothing was changed that caused this. it just started randomly doing it and seems air temp related. this rarely happens. usually the car starts up fine or starts up and stalls 1/2 a second later and then is fine on restart.

[Ninja Mihail]

IS THIS A SPEED DENSITY TUNE OR DOES IT HAVE A MASS AIR FLOW SOUNDS LIKE A 02 SENSOR STARTING TO GIVE UP ON YOU NOT YELLING FOR GOT TO TAKE CAPS LOCK OFF IM BAD ABOUT THAT :doh:

[BLK95TA]

its a 95 with the stock MAF. would the bad o2 sensor cause the car to startup and immediatly die? that's the other half of the equation. sometimes it will do that as well (actually it does that probably 10x as often as it does what you see in the video above)

[Ninja Mihail]

its a 95 with the stock MAF. would the bad o2 sensor cause the car to startup and immediatly die? that's the other half of the equation. sometimes it will do that as well (actually it does that probably 10x as often as it does what you see in the video above)

I have had o2 sensors do strange thing not make it die but idle a 300 rpm before look at your mass sensor closely make sure there isnt any thing on it maybe get some cleaner on it also try cleaning you o2 sensors and iac . my car being speed denisty tuned really depnds on 02 sensors and the map sensor you can check your map sensor gasket and see if its worn out that can cause some false readings by the computer . when it runs like shit does it smoke black

[Ninja Mihail]

man i watched the video again it really points to you mass that my best guess

[Fastbird]

It would NOT hurt to get in there and clean your IAC passages and TB. It may be a sticky IAC and was just hanging low due to insufficient airflow.

[xdeified]

Just out of curiousity. When its running rough, if you rev it does it clear the problem quicker? On mine every cold start causes my car to run as if its missfiring until I Rev it for a few seconds or until I take it on the street. By the time I get to the stop sign its cleared.

Sent from my LG-P999 using Tapatalk 2

[Fixxer99TA]

Not the same vehicle of course, but my 02 dakota 4.7L did the same exact thing (fired up, ran like shit like that, then all of a sudden figured itself out after a minute or so... sometimes a bit more) and it was an 02 sensor.

[BLK95TA]

Just out of curiousity. When its running rough, if you rev it does it clear the problem quicker? On mine every cold start causes my car to run as if its missfiring until I Rev it for a few seconds or until I take it on the street. By the time I get to the stop sign its cleared.

Sent from my LG-P999 using Tapatalk 2

if i rev it it will backfire and pop not clear up. that's why i would normally shut it down and restart it and it would be fine.

[purplt1]

I would try cleaning the iac like said before.

[quik95lt1]

get a scan tool on it datamaster is free for 30 days id use that........watch the timing and the iac counts somethings up and for it to clear up like that im saying its EFI related, it sounds like the ecm is starting up on very low timing and then reverting to normal timing shortly there after.......if it was an iac issue giving it throttle would fix the problem.......you have a raw fuel smell when it does it out the pipes?

[BLK95TA]

not sure on the raw fuel smell. this doesnt happen very often. most of the time it does the stall right after startup thing and then is fine. im thinking thereis a fuel leak down problem. after i pulled it out of the garage and shut it off i started it back up to see what it would do and it immediatly stalled.

[cholmes729]

Opti spark. Just sayin

[BLK95TA]

was cool out today and it started and stalled about 4 times before it stayed running.

[96LT1355Z28]

I haven't gone through your other thread so sorry if this is a repost but have you checked the vacuum line from the intake to FPR for fuel? Whats the fuel psi doing when this happens? Like Mike said, try get a scan tool and watch what the O2's and IAC are doing when it occurs.