Chevy & GMC Vans

For some time my 90 Safari has been plagued with a high idle speed that I can't seem to reduce . Believe its caused by a sensor or something of sort and don't know where to start with this issue . Can someone point me in the direction . Thanks for your timely response.

when i purchased my 92 astro. it had a high idle as well. It turned out that there was a vacume tube that went from the pcv valve on the valve cover to the front of the TBI that was missing. I replaced the tube and pcv valve (inexpensive parts) and the idle returned to normal.

So you may have a vacume leak somewhere.

In speaking of vacuum leaks could be possible and will dig deeper and look for such . Did have some weird noise sometime ago going down the highway , it kinda sounded like my van was running a blower . Some sort of whistle came for a short time then disappeared , shortly after had this problem of excessive idle . My timing is dead on the money . Perhaps I''ll perform obd test for codes . Thanks for the tip .

A simple way to check for a vacuum leak is to have the engine running & supply a fuel source to the suspected areas of vacuum leaks. (fuel sources being - aresol brake cleaner - propane - butane) This type of fuel is airborne & will go into the engine with the vacuum leak & cause the engine to rev up. Once you determine the source, you can then determine how to fix.

Once is enough to post a response.......

justice wrote: It turned out that there was a vacume tube that went from the pcv valve on the valve cover to the front of the TBI that was missing.

Yep.. happened to my mom's truck when she got it from the shop (it was disconnected )

Water Boy wrote:Once is enough to post a response.......

I'll say
I come back & check & I find this......

Thanks there v8famvan sure did adsorb that one . No excuse for missing a good answer . LOL

Well the idle issue has me stumped . Had some change after replacing EGR, PCV, IAC, fixed leaky hoses etc., and this week it has worsened. The idle is intermittent up and down at times , usually up. When driving at around 49-52 km/hr the motor kinda pulses as if an injector problem , but they seem to spray uniform when watching. When running for some time at "normal temperatures", for the first time SES light came up when what appeared was shifting up or down from 1st -2nd and stays on till you come to a near stop then goes out and everything smoothes out . This problem has me confused , obviously overlooking something, would a MAP sensor cause me such grief ?

Well what code was set that caused the SES? Let's start with that one...

v8famvan wrote:

Water Boy wrote:Once is enough to post a response.......

I'll say
I come back & check & I find this......

LMAO, I'm guessing WB was having posting problems

NotDadsW41 wrote:Well what code was set that caused the SES? Let's start with that one...

Good idear NotDads . Didn't have a chance to check the codes lately but will today weather is a little better. In the past when problems started No Codes will come up other than code 12. Will get back after the check because I'll be supprised if any show up. Thanks for the input.

NotDadsW41 wrote:Well what code was set that caused the SES? Let's start with that one...

Good idear NotDads . Didn't have a chance to check the codes lately but will today weather is a little better. In the past when problems started No Codes will come up other than code 12. Will get back after the check because I'll be supprised if any show up. Thanks for the input. Well NotDadsW41 did a test from the ALDL block and came up with code 12 , code 12 , code 12 , and after a long wait and scratching both heads a 3 flash pause 3 flash came up telling me MAP sensor. Man I hope that this clears up all my nightmares . Thanks again. I'm sure I'll be back , LOL

Ever got this resolved?

My '90 would idle high due to the O2 sensor. It burns about a quart of oil every 200 miles. That clogs up the O2 sensor. My mechanic has one of those high-dollar scan tools and it showed a slow response from the O2 sensor.
Use the AcDelco sensor.
Do not use a Bosch.