Tested the ECS... ~10000 ohms at ~34F, so I assume that's close enough. Please advise.

Also, is there any way to adjust the throttle screw without a bi directional scanner?

 

yeah.. but it could also have a short to the block which would screw up the reading for the pcm. Did you test for that?Yep... follow the exact directions and when they tell you to command IAC closed remove the IAC physically from the throttle body and plug or tape over both ports.
- or what I did. Loosen IAC bolts a couple turns. Remove Air tube from TB. slide a .002 or so feeler gauge in between IAC and TB so it covered inlet hole. snug the IAC bolts.
It's six or a half dozen as to effort, IMO

 

OK. Will test for a short to the block.

And I forgot to say earlier the intake ari temp sensor tested ~9500 ohms, so I assume it's ok too.

Also thanks for the info about blocking off the IAC. Sounds simple enough... Can somebody post the actual procedure for setting the throttle screw?


Thanks for all the help...

 

bump...

 

Wait a minute.. exactly what are you trying to resolve by doing that?
You do understand you cannot lower idle speed that way, right? The stop screw sets THE MINIMUM RPM with throttle closed.

The reason it's not a good idea to mess with throttle stop is it screws up PCM baselines. For instance the TPS idle voltage.
Before you do that you have to resolve operational issues.
The PCM wants the engine to idle at 600-650 rpm when in closed loop. It will make it do that unless it sees a serious problem. OR there is a vacuum leak. OR the IAC is sticky/stuck.
Before you mess with it, make sure the IAC is operational. The throttle plate and bore is clean, all the way around and that TPS voltage ... which is supposed to be .5 to .9 volts...is out of range
THEN when the engine is up to operating temp, plug the IAC inlet as I descrbed -reconnect and tighten air tube- and see if it idles between 550 and 600 rpm in park. If it does, the idle screw is set right and anything you do to it can only screw things up. Some lope is not unusual.

If it idles higher than 600 rpm {AND esp if the TPS voltage is .5 to .7 volts} then you likely have a vacuum leak.

 

That's all I wanted to know, 550-600 RPM in park is where it is supposed to be with IAC blocked off.

I'm trying to solve a no idle issue... dies out when you let your foot off the pedal, but will run at 550-600 RPM if you hold it there with the gas pedal.

The high idle thing mysteriously came and went... no idea why. I've done everything short of replacing the IAC to verify that it is operational...

 

The ecs is not shorted out to the block. Checked that.

blocked off the IAC and it still would not idle at all. put a toothpick between the stop screw and the throttle arm until it was at about 550 rpm. the tps reads .84 volts with the toothpick in.

does the screw simply need adjustment or ???

thanks for all the help!!!

 

Excellent work... now think about what you just proved. The truck will idle at 550 without the IAC. AFTER you opened the throttle a little to let more air in.

Tells me the IAC isnt working.
Drop the shim out and read the TPS, if it's above .5 v leave it alone and find out what's with the IAC.

You COULD measure tps with no shim. write it down then adjust screw till tps reads .85. When you get the problem fixed then adjust it back. Do not touch the tps screws till then.

 

Ok. will look at TPS voltage.

Thanks!!!

 

Adjusted throttle stop screw until it would idle at 500 rpm with the IAC blocked off.

It generally idles fine now, between 650-850 RPM depending if it's in gear or not.

But it will randomly idle high when you restart it. Usually if you turn it off and restart, it will idle normally.

Would these be symptoms of ???


Thanks