D'Z28

z28 with 129k new plugs new wires fuel filter ,map sensor and oil change also a new coolant temp sensor car has me stumped when cool runs fine warms up turns to crap till next morn fire it up runs like a lt1 should then back to bs any ideas

Z28silverstreak

What kind of water temps are you running after it's warmed up? If you're having circulation issues of some kind the LT1's do not like a whole bunch of heat. I would recommend using some kind of live data scan tool, because there are 2 different coolant temp sensors, one for the gauge and one to send to the PCM. I would see what temps the PCM is receiving, because if it thinks it's too hot it will retard your timing...a lot in attempts to cool off. Also do you have any misfires or anything?

D'Z28

170 on water temp backfires thru exhaust bank 2 lean sometimes will clean its self up and run for a bit but right back to running like crap

joelster

Which coolant temp sender did you replace? The computer runs off of the one in the water pump. They do go bad, not at all uncommon. Once the car is warmed up it will still be running in enrichment mode if that sensor is bad, and it will stall out and be pig rich. If that sensor is fine jack up the car and unplug the o2 sensors and see what happens. If one of your o2's is bad the same symptoms could happen. Both of these things could be seen with a scanner like a Tech 2.

D'Z28

One in water pump was changed its proly due for o2 sensors car has 129 k on clock only had her for 5 days gonna check a few things b4 i start replacing parts

Guest47904

Disconnect one of the front (you didn't tell us what year or anything else) O2s and see if the problem clears up after it's hot.

D'Z28

94 Z28 all plugs firing have brown tint to them unplugged 02s made no difference . once it reaches temp and hangs there for a few acts up so im thinking somethin in ignition icm ,coil so n theory gonna run it till it acts up pull icm go test it see if breaking down when up to temp

Injuneer

Have you scanned the PCM for codes (they don't all turn on the SES light)? How do you know Bank 2 is "lean"?

D'Z28

Ok hears what we found tonight massive miss number 5 running rich as all get out icm tested 6 times got slower as we went along ran for bout 10 mins died can smell gas wont start smells flooded so gonna change plugs and pull o2s to check them seems to b runnin rich when it is runnin heck idk im over it

D'Z28

NEW DRIVERS 02 , icm cold fire up runs like new shut it off after bout 45 min have to let cool b4 trying to start also 4500 rpm stutter what gives fp 42 no missin till 4500 out of ideas scans show nothing out of ordinary

bw_hunter

Stutter at mid to high rpm...test the opti

D'Z28

New napa coil no more stutter still got cooling times b4 restart from normal operation

slick1hunting

Might want to check for leaky injector.

bw_hunter

I'm not sure what you're telling us here. Are you saying it won't restart right after you shut it down?

D'Z28

Injectors r good since its cold i'll warm it up 10 to 15 mins then its about 20 min drive to town so lets say 45 to 50 mins b4 i shut it off after stoppin here and there . if i try and restart it she wont fire if i sit there 30 mins or so sometimes longer and let cool off a bit she will start right up after she primes up