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TBI not wanting to idle at start up

Kay86K5

Kay86K5

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Hello again all. If some of you remember, I went through a TBI motor swap on my '86 K5 multiple months ago. Motor is a bone stock 89 TBI350 with the '89 700r4 bolted behind it. I bought a wrecked '89 k5 and pulled everything from it and swapped into my '86. I used the factory '89 wiring harness and re-worked it/spliced it into my '86 harness. I finally got the thing to run great after some hickups.

There is one thing that I can't seem to figure out and havn't really taken the time to research until now. Everytime I go to start the motor up, it doesn't like to idle. I have to keep my foot in it, just barely, to get it to start and then slowly let off the throttle, then it will idle and run great. Without this it will not want to start and idle. Everytime I turn the key off, it will do this.

I am wondering if I need to look at my wiring again, or if someone has had this before and knows any tricks. Just about every sensor on the thing (including new cap, rotor, plugs, and wires) is new except for O2

Any ideas? Thanks!
 
What chip is in it? Trying to find out if it's Auto or Manual and what you have?

Is the Park/Neutral Switch hooked up?

Do you have a scan tool to see IAC counts? What are they fully warmed up after a drive in Neutral and Drive?

You could try turning the throttle stop screw in 1/4 to 1/2 turn. This is not an idlem screw, idle RPM is handled by the ECM, it's a Min Air Screw.
 
eagle mark said:
What chip is in it? Trying to find out if it's Auto or Manual and what you have?

Is the Park/Neutral Switch hooked up?

Do you have a scan tool to see IAC counts? What are they fully warmed up after a drive in Neutral and Drive?

You could try turning the throttle stop screw in 1/4 to 1/2 turn. This is not an idlem screw, idle RPM is handled by the ECM, it's a Min Air Screw.
Click to expand...

100% stock chip for Auto. Everything is stock. P/N switch is hooked up and working correctly. My dad has a code reader and when I hook it up, it shows no codes (which I like :D) however I have not hooked up tunerpro to see what is happening, maybe that should be my next step.

Where is the throttle stop screw located? I may give this a try and see what happens

Thanks for the response eagle mark, you are always a wealth of knowledge for injection :thumb:
 
It's what most people think is the Idle Screw, it may have a cap over it.

What happens with age/wear is the throttle blades close and your problem happens. With the scanner you could see a very high IAC count.... all the air going through the IAC and hardly any past blades mixing the fuel with air.
 
Thanks Eagle Mark. I will give that a shot. And I need to get a scanner tool :doah:
 
eagle mark said:
It's what most people think is the Idle Screw, it may have a cap over it.

What happens with age/wear is the throttle blades close and your problem happens. With the scanner you could see a very high IAC count.... all the air going through the IAC and hardly any past blades mixing the fuel with air.
Click to expand...

Just for future reference of people who may have this same issue, its seems as though this may have worked. I popped the small cap off the drivers front of the TBI unit (recessed in just a little bit) and screwed it in about 1/2 turn, maybe a little more. It seems as though it will idle now right at start up.

Before, when I would turn the key on, the fuel pump would prime, and it would crank just fine, and fire just fine, just not idle without my foot in it just a little bit, and eventually would die very soon after start up. Now I don't have to touch the gas and it will fire and idle right away at 500-550 rpms....like it should.

Thanks again eagle mark. You are the man :thumb:
 
Was the plug already gone? Unfortunately people think/thought you could adjust idle this way, unless the motor is changed (or something else is wrong with the motor) you should never have to touch it.
 
dyeager535 said:
Was the plug already gone? Unfortunately people think/thought you could adjust idle this way, unless the motor is changed (or something else is wrong with the motor) you should never have to touch it.
Click to expand...

No, the factory plug/cover was still there. I popped it off and adjusted it. I know that this was set from the factory and the ECM is really what adjusts idle, however, after adjusting this and seeing the results, I would say that what Eagle Mark mentioned before of, "What happens with age/wear is the throttle blades close and your problem happens. With the scanner you could see a very high IAC count.... all the air going through the IAC and hardly any past blades mixing the fuel with air" would be correct and you can adjust this screw to fix a problem that I was having.

As I said, right after initial start up, if I would keep my foot in it, it would eventualy start to idle and run 100% like it should, just not on initial start up
 
Remember, this is not an idle adjustment screw, this is a minimum air screw!
 
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