91ToySR5

hey all... i have a 91 toyota p/u sr5 with 3.0 v6 5spd 4x4.... when i come to a stop (usually will just put it in neutral and brake to a stop) my idle is dropping to 300-400 rpm and you can hear the engine misfiring. if i tap the throttle it'll go back to the normal 800 rpm and run smooth as glass. sometimes it'll drop lower than that and stall if i don't tap the gas fast enough. i can also duplicate it by revving the engine while stopped, when the rpm's come down it'll do the same thing. oh - and this only happens once the engine gets to normal operating temp. when its cold/warming up it has no problems what so ever.

i have checked my timing - ok, put new ignition wires on no change. checked the coolant temp sensor as per fsm ok. i swapped my afm with a spare, no change. i checked the dashpot as per fsm and is in spec. checked throttle position sensor as per fsm, ok. the engine was replaced approx 6k miles ago for unrelated reasons and it did the same thing.

i really don't know what else to check. really hope someone can help me out. thanks in advance!!

rob

abecedarian

are you getting a check engine light while the engine is running or have you tried pulling any trouble codes?
have you checked for any vacuum leaks?

SLOWBOOST

mine does this every once in a while too, my case is the idle adjustment screw backing out slowly from engine vibes. all it takes is a couple turns and back to solid.

91ToySR5

thanks for the replies guys - there is no engine light on and i've checked for codes - none... the idle set screw seems to be ok - it is very difficult to turn by hand... gonna put some new plugs in it tonight not that i think its the problem but its been 2 years so can't hurt... can't tell that there are any vacuum leaks, had some before around the injectors but bought all new grommets and o-rings..

thanks again

SLOWBOOST

you would have to turn it with a flathead. they can loosen up but still be tight by hand.

thook

What were your findings on the coolant temp sensor? IE, the ohm readings.

If you strongly believe the coolant sensor is good, it sounds like a throttle body/intake issue to me. Maybe the dashpot affecting throttle release/idle return.

http://personal.utulsa.edu/~nathan-b...93throttle.pdf

91ToySR5

i suspect the dashpot as well. when i do the check in the fsm - plug hole, race to 2500 and release throttle it does drop to 2000 rpm, but if i do the 2500 drop w/the hole unplugged it usually drops to the 200-400rpm range and runs rough. where is the "VTV?" i've noticed that the a/c idle up doesn't work either - tho i don't have the system hooked up anymore.

thanks again

91ToySR5

ok - as mentioned above, idle screw is tight - can only turn with a screw driver - i have checked the vtv's, all working as per fsm. the coolant temp sensor at normal operating temp (just went by guage on dash not a thermometer) was .3 or .4 as i recall. it intersected on the graph in the fsm.

tested the distributor - air gaps were all in spec .38 max on one side - spec is .2-.4

tested resistance of pick up coils - spec 205-255 ohms

G1 - 255 ohms
G2 - 255 ohms
Ne - 258 ohms

seems like the pick up coils are at max resistance, one over max - fsm says should replace distributor - thoughts?

91ToySR5

just wanted to give an update - if i unplug the vac. line to the egr valve the problem totally goes away. have been driving it for about 2 weeks now like that and no problems. i plug the vac hose back in and it starts all over again. i'm guessing the modulator valve for the egr is messed up...