Rough idle and stalling

[enjoi.this]

I just got the engine back in the car this week. Replaced the head gasket with a thicker cometic along with new gaskets on the top end.

When I fire it up it completely cold it seems to idle fine with a AFR of 14.7 but after about 30 seconds of run time the AFR drops to 10.0 and starts missing until stalling out. I can keep it running if I hold my foot on the gas but still misses and runs super rich.

There are no codes or leaks in the intake system and timing is set (to the best I could get it). Rechecked cam timing also. Im stumped as to why it wont run normally. so any input or suggestions would be great!

Edit: One thing that has changed since last year is Im not using the lex afm anymore since I have maft-pro. So Im running it on a stock AFM and 550 injectors to try and make it run right before hooking up maftpro.

 

[91Supra313]

I didn't know you needed an AFM when you run Maf-T Pro. Sounds to me like a nice little vacuum leak. Check all the vacuum fittings and make sure you didn't miss one or put one on the wrong connection.

 

[enjoi.this]

Maft pro is by passed right now since it wont run at all with it. Thats why Im using the AFM to try and trace this down.

Went through all the vacuum lines too with a diagram so they are all right.

 

[mkiiichip]

BHG may have toasted the o2 sensor driving it rich in closed loop. Try disconnecting it.

 

[jetjock]

You're running a stock AFM and 550 injectors?

 

[enjoi.this]

I never had a BHG just put in a thicker one since it was too high compression for what I wanted. I did try disconnecting the O2 and it just ran richer..?

@jetjock

I only running the stock AFM right now with 550's because I sold my lex afm. Will be going right to maft-pro once this is all sorted out.

 

[enjoi.this]

I tried unplugging the AFM just now and started it to see what happened. Seemed as tho it smoothed the idle out a lot and it ran for longer before dieing. Probably ran for 1.5 min compared to 30 seconds..

 

[enjoi.this]

I tested the AFM elctronics with an OHM meter today and the Temp side seemed had open circuit both ways.

Also tried running the car with AFM unplugged and idled normal. While it was running I plugged back in the AFM and it immediately started to run shitty then stalled. Sounds like that is more the likely the problem. This will be the second one in 2 years...

 

[jonahs_supra]

my last afm did the same thing
ran like dog shit but if i unplugged the afm it would idle better
replaced it with a new 1 and no more problems

 

[enjoi.this]

Seems like im going to be replacing it again here if I cant get the speed density working. really starting to annoy me big time.

 

[jonahs_supra]

i dont blame you
i went through 3 used ones in a matter of 6 months...
decided it would be wise to just suck it up and buy new
now im going speed density with my hks vpc in 2 weeks lol

 

[enjoi.this]

wow eh now that really sucks!! haha

how much did the new one run you?

 

[90mkiiisupra400hp]

Did you ever figure this out? I am having the same problem, I wired up my Maft Pro and idle goes way rich and stalls out, so I bypassed the Maft and went back to lex/550 and same thing, but I am getting code 21(o2 sensor), I put in a good o2 sensor but the car still won't idle. Just wondering what fixed your problem cause it sounds just like mine. Thanks

 

[enjoi.this]

The AFM was no good. It pooched out after the car sat all winter. Installed another known good afm and boom ran perfect.

 

[SupraBog]

I went through about 3 AFMS before I gave up and decided to go MAP ECU. Still tunning it now with a wideband but man what a pain to deal with the stock AFMs. Some people have said that the oil from a K&N filter would mess those up.