first off, i drive a 91 t/a l98 and was wondering if anyone could help me out with my problems.

first off, i bought the car with about a month on new plugs (bosch platinum; i dont know if that could be the problem or not) cap, rotor, wires, and a fairly new o2 sensor (also bosch)

the thing is, when idleing in park or nuetral, i notice that the motor will stumble every once and awhile then recover, then in another few seconds, repeat. it doesnt effect the cars performance at all, and the car has great power, but just when its idleing, it'll stumble around and run kinda rough.

but thats not it, mabye once a week, it'll take awhile to start up (it always does, but it craks for a few seconds before it does). and it'll do this 2-3 times then be through for another week or so, then do it again.

and lastly, once every few days, when i go from nuetral or park to a drive gear, it will die.

sorry for the long post, but i've tried plenty of things and out of ideas. its got fresh oil and filter. the k&n is dirt free AND free of excess oil on the k&N. ive ran plenty of injector cleaner in the tank, not to mention feeding 1/2 a bottle of seafoam through the brake booster line into the intake. and also ran a 3 part fuel emmision system cleaner from grease monkey (my old work) in it around 3k ago.

thanks guy, i look forward to hearing your expertise.
later,
mike

 

ok well first off...bosch sucks..ditch that o2 sensor for an ac delco one...our cars like nothing but a/c delco ones.

Sounds to me like theres a miss from your discription, but its hard to tell. Check that cap and rotor and make sure its good.

Also try resetting the minimum air as well. You can try also pulling the iac and cleaning it up. This may help the neutral/park stall

Honestly just sounds like my car. I have all those problems..but its b/c my car has a cam in it lol. Acts just like yours though. Don't take this the wrong way...but are you sure the car doesnt have a cam possibly installed?..without tuning...it might cause the stalling and such.

 

yeah, its got a cap and rotor, ill replace it again if i have to though.

and how do you "reset the minumum air"? sorry, im a former mustang guy, so this chit is kinda still new to me.

 

haha dont worry about it

well here's how you do it..

jump the diagnositc terminal and turn the key without starting the motor. If you go near the throttle body...you should hear a clicking noise. This is your iac opening. Wait about thirty seconds. Turn the key off. Then pull the plug that goes to the iac off it. Now start the car...the idle should be around 400rpm..if its not, adjust the idle screw till it hits that. Then shut the car down. Plug the iac connector back in and fire her up. the ecm will then mess with the iac until the car hits a steady 600rpm idle (for unmodified cars)
----------
oops forgot...Im guess you probably dont know where the iac is..

Look at the throttle body from the front...now look at the passanger side of it. Youll see two sensors on the tb and 2 plugs off the harness going to these sensors. The top one is the TPS sensor..the bottom is the idle air control valve (iac)

 

yeah, i know where teh iac is, but ok, ill give that a shot as well. do you think my ignition control module would have anything to do with it?

 

its a possibility. That could deff cause a miss at idle, however i figure if it was..you'd be having more problems at high rpm and such.Try pulling it, cleaning it up..and putting new die electric grease on it and mounting it back up.

 

check for leaks, make sure your running good gas in it like he said clean the iac if the ign mod was going bad then you would probably get a code 42 pop up. one thing to check is cracks or splits on your wires make sure there not laying on anything that can burn a hole or cut them.

 

i would dump those bosch plugs too. a good set of standard A/C delco plugs will work just fine, no need to spend extra money for platinum.
the CR45 plugs in my car have been doing just fine for well over 60.000 miles.
the next set i put in will be CR44.

 

I heard the Bosch Platinums get very hot, hot enough to burn any gunk off the tips of the plugs?

 

Sounds like it's just the O2 staying cool, and sluggish (but still triggering closed loop). Or perhaps the old injectors are hitting a low pulsewidth, and not flowing linearly at all (flow rate drops much faster than the PW). Could be an exhaust leak near the O2 as well. IAC out of adjustment won't cause this, but a lack of a P/N switch input would cause the stall when put in gear.

 

nah, the injectors were replaced not too long ago. and whats pn switch input? lol, like i said, i know my fox bodies, but not my thirdgens yet. please eexplain to me what this is.

oh, and the 02 censor isn't too old either, but its bosch, should i replace it anyway?

im picking up new plugs tomorrow, what kind should i get, and what should i gap them at?

thanks for the help guys

 

Not too OLD, too COLD O2. Many recommend the AC Delco O2 sensor over Bosch. If you're running headers, it's highly recommended to switch to a heated style 3 wire O2 sensor (just wire the two white wires to switched 12V (~10amp source) and ground)
P/N is the Park - Neutral switch. It tells the ECU if it's in park/neutral or not, and adds IAC steps quickly to avoid stalling when put into gear.

Raising the minimum air (open the throttle blades more - using the idle screw) can help make the problem go away, but probably isn't the direct cause.

 

carbed87 Pretty much described my car exactly lol.

I've got an 88 MAF 350TPI car..


Ive got a miss from what it sounds like at idle and an idle that is described just like carbed had explained. Even stalls sometime when going into a gear. Im assuming cleaning the IAC will help me out aswell? What exactly should i use to clean it out?

 

just take some break cleaner and a rag...and just get all the deposits off it.

 

nah, ive cleaned my iac plenty of times, and it's still being a *****. mabye the sencor is bad?

and whats the recomendation on the type of plug/gap for my car?

 

ttt?

 

ttt

 

AC Delco's R43TS's, gapped at .035 will do you just fine, but I'd be thinking about the IAC aagin, almost seems like it's sticking/hanging up.

You could continue to toss parts at it, but if you can get a scan tool and monitor a few things, you may narrow it down first.