s14 hesitating and stalling

[sushi]

my 98 s14 struggles and dies when it hits operating temperatures and i can't figure out whats wrong with it. it throws no codes and everything else looks fine. what confuses me is that when i had hotshot header on my car it ran fine, but when i put the stock manifold on with the stock cat, the problem starts again. when its about to die, i can smell that its running rich from inside the car. when it starts hesitating and if i try to keep the rpm up, it shoots out black smoke. if i let off the gas pedal, it dies. do i have a clogged cat? or something else, please help

[Rezlo]

Everything besides the header points towards a bad coolant tempreture sensor, but you might want to check your cat, there is a real simple way, most exhaust shops will drill a tiny hole before the cat and monitor the presure coming out that hole when reved up on a lift, if its not to presurized when reving they just weld the hole closed, if not then obviously you need a new cat (it would seem unlikely as clogged cats will cause it to run bad hot or cold), Could also be the O2 sensor but not extreemly likely as they normaly throw a code.

I would look first at the twin wire ECU coolant temp sensor, (single wire sensor is gauge) its like $12 from a parts store and causes numerous hot running rich conditions.

[Buffalo Daughter]

could be your egr thats closed. Could be your cat but you should shake it if it rattles that could be toasted already. DO NOT DRILL A HOLE. What they do to diagnose that they unlug the o2 sensor in the exhaust itself, not the one in the manifold, and hook up a gauge through there. It sounds like something is being plugged. Could be your temp sensor since your car dies on start up.

[Rezlo]

If you want to check if its the cat you have to unplug or make a hole (which then gets welded shut after and retains both O2's for correct readings as done by 90% of exhaust shops) BEFORE THE CAT, but if its the cat it would do it all the time, not just when its hot.

EGR open causes problems EGR closed isnt a problem, and 95% of the time it will throw a code for EGR flow error's so its more than likely not EGR

Temp sensor...

[sushi]

engine temp. sensor and both o2's have been replaced.

[Buffalo Daughter]

If you want to check if its the cat you have to unplug or make a hole (which then gets welded shut after and retains both O2's for correct readings as done by 90% of exhaust shops) BEFORE THE CAT, but if its the cat it would do it all the time, not just when its hot.

EGR open causes problems EGR closed isnt a problem, and 95% of the time it will throw a code for EGR flow error's so its more than likely not EGR

Temp sensor...

you do know that if the egr is stuck completely closed that you'll have detenation and melt your cat, Plus fuck up some sensors along the way?

[sushi]

i shook the cat and it doesn't rattle the temp sensor was replace <1000mi. still hesitates and shoots black smoke out of my exhaust. oh and this only happens sometimes, not always. 75% of the time it drives perfectly fine.

[Nightmare]

I have a similar problem. My BPT valve needs to be cleaned and my idle control valve needs to be replaced.

[Sanchi]

Alot of ppl get this problem with their s14. The VERY first thing you should check is your throttle body! Pull out your intake and see if that sucker is clogged up! Most of the time its just that dont think too much into it. My car was haveing the exact same problem. And it would go away for like acouple of months then return twice as bad!! even in high speeds if i let off the gas it will want to choke out and die.

If your throttle body is jammed up in GUNK it's not gona open and close right. That would explan the hesitating and stalling up the mofo. Not to mention when you let off the gas it dies. It cant idle if it's gont shit clogged all up in it! Get some cleaner a tooth brush and a towel... wipe that shit clean!!

Hope that is your problem!!