420A Weird idle Help!

[Seth Schneider]

okay i bought this car as my first car a month ago but it had a high idle, 3500 to 4000, anyways the previous owner said to just turn the car off and pull the actual throttle on the tb full throttle and let go and it will go away, and sure enough it did, and he said it only does it when you mash the gas pedal. also when you tap the gas the car revs up but takes longer to get back down to idle speed it’s not super slow but it’s noticable, also me and my buddies took it for a spin the other night and it did the high idle again and i did the same thing and it went back down, any help would be appreciated. Thanks!

 

[Seth Schneider]

i also checked the pcv valve and it’s working fine

 

[dustyboner]

I have a bunch of extra 420 parts if you don't want to buy new.

I would remove the throttlebody, open it all the way and let it snap closed. Do this a few times to make sure it fully closes every time. Make sure the metal piece on the end of the shaft (end where the cable attaches) contacts the stopper when its closed.

If all that is okay, reinstall the TB. don't reconnect the air intake tube. start the car, let it run for a minute or two. then with it still running, put your hand over the throttle opening, the car should die right away. if it doesn't you have a vacuum leak. to find it, reconnect the intake tube, pull of a single vacuum line, cap the nipple and see if there is any change in your idle. if no change, pull the cap and reconnect the vacuum line. do this for each vac line on the intake manifold (pcv, brake booster, and the three connected to a single fitting) and also for the one on the throttle body.
if none of them change the idle, get a can of starter fluid. with the car running spray on all the possible leak points on the intake manifold, like where the injectors go into the manifold, map sensor, upper to lower manifold gasket, egr tube. you will notice a change in the way the engine is running if you spray it on a leaking area. you can also spray on around the throttle body

 

[Seth Schneider]

my tb closes all the way, and i know i don’t have any vac leaks as i just went out and looked for some today, i’m going to buy a new tb as the guy said above it could be my shaft seals.

 

[dustyboner]

You have a 420a motor. The 420a throttle body has no shaft seals. The TPS has an o-ring that seals that end but only to keep shit out of the TPS not to seal from vacuum leaks. there are bearing pressed into the housing. they are just like skate bearing but a little smaller. The center of the bearing rotates with the shaft. This minimizes any wear to the shaft.

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[Seth Schneider]

interesting i don’t remember seeing that when i changed my tps

 

[Seth Schneider]

also, if i were to have a vac leak wouldn’t the car idle super bad