missing and popping during warm up

[tb3]

On a engine cold start up, my 84 gn will start right up and run smooth for about 20 seconds, then it will idle down and run rough till it (I'm assuming) warms up (about 40-60 seconds). Sometimes if I give it too much gas during the warm up time, I can hear a backfire through the air intake and the engine hesitates. Its not throwing any codes. My service engine soon light does work, I went ahead and plugged my diagnostic in and it just did the code 12 (everything is normal) light at me. Its been doing this for a while, even before I did my 87 coil pack and module conversion. I pulled my Egr, and don't see anything clogged, its pretty clean actually. I pushed the diaphram up and down with my fingers and it seems to feel normal. The diaphram isn't leaking, its holding tight if I put a vacumm on it and my finger over the hose port. I checked ALL my vacumm hoses for leaks. All my vacuum/boost lines are new, and I have used zip ties (with locking metal tab) on all the ports for a good holding seal. Unfortunetly I haven't done my 87 ECM conversion yet so I don't have ability to use my directscan. (I'm waiting on a response from Turbotweak.com about a chip enquiry). I've been doing some reading/troubleshooting on this for a few weeks now. Something else I've done was pull the wastegate and egr contollers off my driver side valvecover and cleaned them up and made sure my electrical connections on them and the connectors where not corroded. I sprayed the connectons with contact cleaner before reinstalling. Otherwise the car runs/idles great right after that little warm up period. It won't do it again unless the engine has cooled down. I was going to wait and post about this after i've done my ECM conversion to see if the problem went away. But that may be another couple weeks now. Does anybody have any suggestions? thank you in advance.

 

[cool 84]

Backfiring through the intake is almost always a lean condition. If you have a scan tool watch what the temp sensor is reading as it warms up. What chip are you running?

 

[91rangerturbo]

my car does the same thing for the first 1 min or two tops. Until it warms up. It will cough and sputter a little. I am running stock chip and everything. Only mods i have are a 3" mease dp, atr up pipe, Adj reg, hotwire 307, K&N air filter. Stock Chip and etc..

 

[tb3]

It has the stock chip and ECM. Also has stock injectors. I haven't pulled them or tried to clean them because I kind of ruled them out being this only happens during that little "warm up" period. I also definetly do not have any air leaks inbetween my mass air flow sensor and the throttle body. A few weeks back I got a code for a "O2 sensor sensing lean condition". After close inspection of the stock factory plastic air intake pipe, I noticed about 4 huge cracks in the "accordian" section of the pipe right after the mass air flow sensor. I replaced it with a aftermarket aluminum pipe and have never gotten that code since.

 

[tb3]

Oh yeah, forgot to mention, no scantool yet. I have directscan and everything I need to convert except for the proper chip. Which I'm waiting on a reply from turbotweak.com to see if they can make me a chip that doesn't need a airtemp sensor.

 

[SPS]

my car does this also. after spending a lot of time trying to diagnose it, I finally figured it out. my fuel gauge is wrong. when it shows to have like 2 gallons left is actually empty. when the tank is empty is always backfires thru the intake. although it still runs good. i have replaced the pump with a racetronics kit but didnt notice anything weird in the tank. maybe its just the way the pump sits in there

 

[tb3]

Mine does it on a full tank so that rules that out for me. I'm kind of wondering about my temp sensor that cool84 mentioned. I'm fixing to do the F-body radiator conversion, so that would be a good time to pull and replace the sensor. I could always put a meter on it too I guess. At this point, I'm going to focus on getting my ECM converted so I can get my directscan operational. I realise it's tough for anybody on here to try and help me out when I don't have any numbers to show just what exactly my cars doing.