IAC
When I first installed my fitech I was able to set the IAC at around 7. My car was running great! I noticed it started to run crappy and noticed my IAC is now set at around 150 and the hissing is really loud. I tried to adjust it and it won’t adjust. The best I got was 130 ish. I can’t figure out what’s wrong. It’s brand new with less than 200 miles on it. Any ideas?
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Are you running timing control? If not, did you shield the blue wire? Check for trouble codes. Datalog the event and post here with Dropbox or Cloud.
Datalog should be approx 30 seconds long, over 170 degrees and at idle.
I’m not running timing control. I’ll take a look at the blue wire and trouble codes and report back. Thank you
Okay, I checked under Fault Codes and it was blank. I checked the blue wire and it is connected to the tach on my HEI. Forgive me as I’m not very technical, but what is meant by shielding? The symptoms that I am having is when I’m driving, it sputters at take off with intermittent signs of running well, it’s like I’m running on a few cylinders and suddenly the others kick in.
Intermittent problems usually fall back to electrical interference. If the ecu receives a dirty or lack of signal, it does not make the right calculations. One very common issue is lack of quality grounds. Try connecting a ground wire from the battery directly to the carb stud. As for blue wire shielding. Plug wires can wreak havoc with this wire. The blue wire is responsible for sending an ignition signal to the ecu for timing of events and rpm. You can find a shielding solution in the Electrical section as a pinned post.
A datalog of events while the engine is running poorly will help a lot.
Got it, I’ll give it a shot and report back. Thank you!
I DID IT! I ran a dedicated ground like you said and fired up the car and let get up to temp. It helped but what did it was the rear adjustment screw on the passenger side. That sucker was screwed all the way down. As soon as I started to adjust that, the motor took on an entire different sound. I got the IAC down between 5-7 and at about 11 when the fans kick on. Ran smooth on the test drive... Thank you!
What adjustment screw on the rear passenger's side? This is the first I've heard about this screw. What does it adjust? I've got similar issues, especially the hissing. Except I can adjust my steps up or down fine, but I always end up with a surging idle. I can hear the unit trying to get on top of it, and it will level out a bit, then the IAC steps start going up and down, until eventually it will go so low that it stalls. In my experience, this almost is always caused by a vacuum leak but I can't find one, except for that open port. I'm pulling beween 11-15mm/hg at idle, when it gets to surging it will go between 10-17. I also wanted to confirm that the vacuum port on the passenger's side fuel pressure regulator is supposed to be left open. I read somewhere that you are now recommending to connect this to a manifold vacuum source. I've been trying to set up the idle for about three days now. I know that's step one. I haven't given up yet, but this thread was close, so I thought I'd ask.
Quote from 7.4 4x4 on May 28, 2019, 10:50 amWhat adjustment screw on the rear passenger's side? This is the first I've heard about this screw. What does it adjust? I've got similar issues, especially the hissing. Except I can adjust my steps up or down fine, but I always end up with a surging idle. I can hear the unit trying to get on top of it, and it will level out a bit, then the IAC steps start going up and down, until eventually it will go so low that it stalls. In my experience, this almost is always caused by a vacuum leak but I can't find one, except for that open port. I'm pulling beween 11-15mm/hg at idle, when it gets to surging it will go between 10-17. I also wanted to confirm that the vacuum port on the passenger's side fuel pressure regulator is supposed to be left open. I read somewhere that you are now recommending to connect this to a manifold vacuum source. I've been trying to set up the idle for about three days now. I know that's step one. I haven't given up yet, but this thread was close, so I thought I'd ask.
What he was referencing is adjusting the secondary butterflies for that they are closed properly when at idle. Sometimes these get a little out of adjustment and are open slightly, causing tuning issues. To adjust, you want to back the front adjustment screw out until linkage quits moving, then adjust the secondary linkage so that it is just closed. Then screw in the primary screw again to achieve correct IAC steps at idle and operating temp.
With that said, many things can cause your issue. Need to know your engine, cam, and settings. A 30 second idle datalog at operating temperature would help also. Start a new Topic.....