Got a 93 s10 blazer vin w. starts fine as soon as you turn the key its on. but after about 10 seconds it starts surging really rough idle almost dies. but when i put it in drive or reverse it clears up immediately. but as soon as i put it in neutral or park it will start surging again. if i drive it around a mile or 2 and put it into park it runs fine NO rough idle. when i turn it off and go into the store and come back 5 minutes later and start it up it will start surging and idle rough again for a few minutes then its fine. on a cold morning if i just let it idle and surge it will clear up in about 5-6 minutes and run just fine untill i shut if off for a few minutes. about 20 degrees F cold
driving around town and highway driving runs just fine.

replaced so far
tps sensor new
egr valve used
map sensor used
iac valve used
dist. cap new
rotor button new

none of these changed anything.
spark plugs looked good

im pretty sure i dont have a vacuum leak

any ideas?

 

You could have a fuel leak in the plenum, take the sensor of the top of the intake and look inside and see if the right side is shinny and clean, if so it a regulator leak. Otherwise you plenum gasket could be leaking.

 

yea i was thinking that since right after i replaced the lower intake manifold gaskets and started it up is started doing this. since i had to move some of the hoses around to get to the intake bolts i might have cracked one of them. but since i cleaned the intake i wont be able to tell if there is gas leaking unless its puddled up.

 

Even thought I don't have one and need one and it seems impossible to barrow one, you should try to get a fuel pressure guage kit and see if it loses pressure.

 

Fuel Pump Tester $19.99

And some say that some parts stores will rent them to you.

 

Smell your motor oil... If the gas is leaking internally, where is it going to go??? Its going to run down and mix in the oil, making your oil smell gassy and probably put it overfull. In extreme cases you can get it diluted down enough to start washing cylinder walls and berrings.

 

turns out that the the injectors are leaking. the oil does smell like gas but not so much overfull. so i think i caught it in time. but i pulled the plenum off today and the whole passenger side of it was soaking wet with gas. so i turned the key on and watched to see if there were any leaks around the regulator and did not see any gas leaking. so im thinking the injector hoses at the base of the spider were leaking. i picked up a cpi unit off a friend for 125 only like 6 months old. he put the new one in his but then the bottom end went out cause i guess his was severe enough it dilluted his oil and messed up the bearings. he aslo gave me a brand new regulator with it. i also ordered a nut kit which is the fuel lines going to the spider off of ebay for 40 bucks. i dont see how the heck your supposed to put the lines back in without bending them? so as soon as i get the hoses i will put it all in and a new oil change and some lucas oil treatment. will let you know what happens.

 

replaced cpi injector assembly and nut kit. primmed fuel and nothing is leaking now. soo put everything back together and it just surges in park again. for like 5 minutes then its all fine. what am i missing? it idles just fine after 5 minutes. or if i do a cold start like in the morning it will surge like its gonna die and run rough, but if i put it in drive or reverse it will smooth out right then. put it in park then it starts surging again. but if i let it warm up for 5 minutes while surging it will smooth out and run like nothings wrong.

 

You take the intake off to put the nut kit on. They press in from the back side. Might as well grab an intake gasket set and some new coolant and something to clean up all your parts like new with...

 

yeah did all that. and it still continues to surge in park and not in drive. what else could be doing that.