Author Topic: High Idle after warm up / Fuel Injected / Transmission clunk shift  (Read 1878 times)

Offline Thundergun

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High Idle after warm up / Fuel Injected / Transmission clunk shift
« on: September 03, 2015, 09:34:39 PM »
Hey everyone. Need a little help here ...

'87 fuel injected 350 in my 85 k10.

I just did a tune up, plugs, wires, cap, rotor. now when i drive it, and it warms up, it idles a bit higher than normal. The worst part is when it idles high, and i shift the trans from park into reverse, there is a huge clunk. However, when it cools down a bit, it idles normal and there is no clunk.

Im assuming the clunk and the high idles are related.

So I'm thinking to start with Vacuum lines right? But I don't which vacuum lines to check or how to check. i gave them a visual and they all look good, except for the 2 circled. And i don't even know if those would affect idle.

Which lines should i check - where are they - and how to check them?

Also i noticed an open fitting without a line on it .. seems like it should have a line ... it's next to the electronics as shown. right side of engine bank.

Thanks for all your help!!

Edit: I searched 'High Idle' and got a lot of hits - but they were all for carbureted engines.
« Last Edit: September 04, 2015, 02:59:45 PM by Thundergun »
1985 K10 Shortbed, 6" Superlift, 33x12.5x15" tires, 100% bad, '87 fuel injected 350 (i think)

Offline Captkaos

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Re: High Idle after warm up / Fuel Injected / Transmission clunk shift
« Reply #1 on: September 04, 2015, 04:01:05 PM »
Top pic is the Cruise control.
Second pic is the EGR Purge, nothing goes there.
Last pic, not sure what we are looking for?

Is the TPS voltage good? .55V
have you tried resetting the IAC?

Offline Thundergun

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Re: High Idle after warm up / Fuel Injected / Transmission clunk shift
« Reply #2 on: September 04, 2015, 05:14:02 PM »
Top pic is the Cruise control.
Second pic is the EGR Purge, nothing goes there.
Last pic, not sure what we are looking for?

Is the TPS voltage good? .55V
have you tried resetting the IAC?

Thanks.

The last pic was just a general pic, see if anyone notices anything out of the ordinary.

I have not tested that TPS voltage. I have a volt meter so i think i can do it. Can you tell me how?

What is IAC?
1985 K10 Shortbed, 6" Superlift, 33x12.5x15" tires, 100% bad, '87 fuel injected 350 (i think)

Offline Thundergun

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Re: High Idle after warm up / Fuel Injected / Transmission clunk shift
« Reply #3 on: September 05, 2015, 10:43:20 PM »
Okay it looks like i figured it out. The line going from the 3-way T has a large diameter vacuum hose going to the master cylinder (i think it's the master cylinder) for the brakes. It popped off when i was backing into my driveway and i lost my brakes! so i popped the hood and saw it. I put it back in and the idle returned to normal. Also i replaced said line - it looked questionable.

See line photo attached with the hose outlined in blue. Thats the one that fell off and i replaced. Idle good to go!

Also the transmission clunk is gone.
1985 K10 Shortbed, 6" Superlift, 33x12.5x15" tires, 100% bad, '87 fuel injected 350 (i think)

Offline Captkaos

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Re: High Idle after warm up / Fuel Injected / Transmission clunk shift
« Reply #4 on: September 08, 2015, 10:59:59 AM »
so everything is fixed?

Offline Thundergun

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Re: High Idle after warm up / Fuel Injected / Transmission clunk shift
« Reply #5 on: September 08, 2015, 02:25:22 PM »
so everything is fixed?

Yessir! See my post right above. It looks like it was that large diam vacuum line going from the 3-way tee to the brake (booster?). It's outlined in the blue in the picture i attached to my last post. The idle is back to normal. The line looked pretty rough, so i replaced it. Also the tranny clunk is gone, which from reading through other posts makes sense.
1985 K10 Shortbed, 6" Superlift, 33x12.5x15" tires, 100% bad, '87 fuel injected 350 (i think)