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Running pig rich and stalls when warm



Damn I was holing I had something there. In hptuners the guage lights up red as a warning somewhere around 50c. Well then ask to my initial question of what would take an perfectly running cold engine to surging and stalling when warm and then the next day when cold to running proper again? Now I could be out driving for an hour and it's running fine but once I shut it off and come back out a half hour later and try and start it, it pukes black exhaust and stumbles to start like it'll start running on a couple cylinders and slowly adding cylinders till it's finally smoothed out all the while pressing on the gas or it will not start.
 
i went for a drive today and as usual, she fired up and drove like a champ. i let’er sit for about a half hour and tied to fire’er up, she started acting all retarded like before. i wasn’t logging but i was looking at my scan guage and i noticed when it was doing that the timing was very low around 5 to 10. then it would go up to the 20 as normal when she smoothed out. so i went back and looked at my last log, and i noticed the timing was doing the same. could something be affecting the timing? earlier on today when it was doing the same thing i grabbed a spare iat sensor and plugged it in to give it lower temps(room temps), and it didn't change a thing
 
I was out playing around after I let her cool down about an hour after a drive. Tried to fire'er up and she was being stupid not starting, so I unplugged the maf sensor and she fired right up. With her running I plugged the sensor back and she would stall out so I'm assuming it's something to do with that. But once the motors cooled like first thing in the morning, she starts up normal. Any idears?
 
Not yet, I already changed it out about 6 months ago. I just wanted to make sure it's nfg, how do I test that? It runs good cold then ****ty warm. But only trying to start warm, once I get it going by giving it gas and it smooths out then it's fine again.
 


with a aftermarket maf? if so either get it replaced, or best bet is to get a used one from a junk yard, they run around 40 bucks and have a 60 day warranty. my jy maf is 4 years old now. best 40 i ever spent.

i think whats happening is it runs fine cold in closed loop, ( runs off the pcm) once warm its in open loop running off the sensors. and the maf is crappy causing it to run badly.
 
Scottydoggs said:
with a aftermarket maf? if so either get it replaced, or best bet is to get a used one from a junk yard, they run around 40 bucks and have a 60 day warranty. my jy maf is 4 years old now. best 40 i ever spent.

i think whats happening is it runs fine cold in closed loop, ( runs off the pcm) once warm its in open loop running off the sensors. and the maf is crappy causing it to run badly.
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I'm not sure if it's aftermarket, it's from a local parts store and not oem. Yeah this is the second new one. They replaced the first one under warrantee after a month. As for the junkyard, ours are out to lunch on their pricing. Sometimes I can buy new from napa for the price those crooks want.

edit: my tuners going to do me a sd tune.
 
The whole setup is a 2002. I'm going to see if the parts store will warrantee it again as it's only bout a year old. I bough new so I hopefully wouldn't run into this type of problems with a used one, you never know what your getting with used.
 
truth is your better off with a used oem maf. aftermarket mafs sucks a donkeys dick. never last more then a few months.
 


what are your fuel trims? with your tuner you can data log the maf output and see if something is wrong. for a given rpm the maf signal should be very similar. if you see maf readings that dont seem right then it is the maf. it could also be a bad O2, or even a vac leak.

but yes there is a problem with being in closed loop. this points to sensors or vac leak. fuel trims should be positive if vac leak.
 
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