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Discussion Starter #1
Bear with me on the noob shit, but I need to get this straighten out.

Fuel system is brand new, tank to the injectors. Literally everything. New ecm, TPS, IAC, new intake gaskets, cap, rotor, wires, motorcraft plugs, cleaned TB, no vacuum leaks, 100% stock down to the emissions. NO CODES. It sat for years and I replaced everything to get it running and up to spec.

It has a rough idle when I first start it. I can floor it and it clears out, but still has a hiccup or three till it gets up to temp. Once it's warm it generally runs fine. I've put about 600 miles on it hoping the new ecm may need to "learn" or something to that effect with no luck.

What am I missing or forgetting?
 

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I know you said the IAC is new but are you 100% sure it is working properly? The symptoms fit. I personally do not know how to test these particular IAC units so hopefully someone who does can chime in.

-Joseph

EDIT: I believe your TPS should have some adjustment. Have you played with this yet?
 

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Have you verified temp sensor voltage/resistance when cold? If it was reading warm all the time it would cause shit idle, stalling, and hesitation on startup because it would think the engine was already at operating temp, and obviously once there thinks everything is great.

Conversely if it was reading cold all the time, it would run super rich because it's stuck in "choke" mode and reverting to cold fueling tables. GM stuff usually reverts to cold when it fails, not sure where the Ford ones tend to go but it's an easy check.

Also verify TPS voltage and adjust as necessary. Not all are created equal and can need a little tweaking.
 

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Get a fuel pressure gauge and check for leaky injectors too.
 

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I know you said the IAC is new but are you 100% sure it is working properly? The symptoms fit. I personally do not know how to test these particular IAC units so hopefully someone who does can chime in.

-Joseph
I've cleaned and tested them by just applying 12V and comparing to a known good one. The plunger moves freely a certain extent when you touch power to it.

The usual symptom I've seen is a fluctuating idle that slowly moves up and down in RPM, almost killing the vehicle on the low end, because the IAC can't compensate fast enough. Usually caused by grunge. My '87 5.0 Mustang was notorious for it and I'd clean it up every 8 months or so.
 

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Discussion Starter #7 (Edited)
The IAC works, I can unplug it and it wants to die. TPS is set to .9 volts (highest it can go) up to 4.2 volts WOT. I also replaced the coolant temp sensor and air intake temp sensor. Cleaned the throttle body and blades.

Same shit different day. Just bounces back from 600-1000 rpm at idle. It drives/run fine. No problem around town or cruise set at 70.

Once again, no codes. I'm leaning towards blocking off the EGR now.

How does one check for individual leaky injector if they're all on a rail?
 
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