Problem: When I start it, it never initially idles up. Immediately after starting it idles at around 5-600. If it is cold, it will die right away unless I get on the gas to get it idled up for a little bit. Additionally, if I rev it high, like 5K, then drop off the gas, it will almost die before recovering to about 500 rpm.
I would suggest posting a LT/ST fuel trims for both banks too.
The "bold" part sounds exactly as a fuel trim reversal looks like.
Cheers,
Mike
The PIDS you want to record are; 1)IAC Counts, 2)Desired RPM, 3) RPM, 4)Desired Throttle Position, 5)Throttle Position.
With the ohm meter your looking for 40-60 ohms across pins A&B and across C&D. Then infinite ohms across pins A&D and B&C.
Might as well try those IAC relearns (one at a time) before you do any testing. Be nice if that solves the problem right there...but I'm not betting on it.
Taking a look at it right now. Ohmed out the contacts. All in spec. 52.6ohms A/B, C/D and infinite for A/D, & B/C.
I only have torque lite for my BT dongle, and it doesn't have IAC counts, desired RPM, or desired TP. Maybe there's a better app? Did the relearns, didn't really seem to make a difference. I guess I was wrong about 500, it idles right around 650 like it's supposed to, but when I get the A/C going (not working yet), that may drop. Fan, radio, and lights drop the rpms by about 50.
With engine warm, and air intake off, there is a LOT of suction going through the iac air hole. (See pic). Is that right? It will barely run, surging up and down with the air intake off.
I would suggest posting a LT/ST fuel trims for both banks too.
The "bold" part sounds exactly as a fuel trim reversal looks like.
Cheers,
Mike
Well, not sure if I have an LT trim in my app, but I put on this FT1x1, and the ST. After a good rev, the ST really drops negative pretty far. Seems to have a hard time stabilizing the trims. Here's a few pics. One at 2K, and one just after falling off after a rev to 4K.
Hey guys, I have to backpedal a little bit... Usually when I start this, it's cold, and it never initially ramps over 700 before dropping to around 600. Now that the engine is good and warm, I'm realizing that it does in fact ramp to 1K right away (when warm) and drop immediately to about 500, then level off at the 600 to 650. Just want to make sure I'm posting facts. It still drops too low (IMO) after a high rev 4-5K, it will drop to about 400 for a sec, stumble sometimes, then level back off at 650. I edited my initial post to reflect this, sorry.
Hey guys, I have to backpedal a little bit... Usually when I start this, it's cold, and it never initially ramps over 700 before dropping to around 600. Now that the engine is good and warm, I'm realizing that it does in fact ramp to 1K right away (when warm) and drop immediately to about 500, then level off at the 600 to 650. Just want to make sure I'm posting facts. It still drops too low (IMO) after a high rev 4-5K, it will drop to about 400 for a sec, stumble sometimes, then level back off at 650. I edited my initial post to reflect this, sorry.
I'm appreciating the input, thank you.
Sounds like your IAC is moving the pintle in and out then. I would next consider the ECT sensor. Also, maybe take your MAF off and make sure you didn't accidentally break loose a side of one of the little resistors from the bars in there while you were cleaning it. With my eyes, I need a 10x loop to see it clearly. Will your tool show you MAF g/s and MAF volts? Will it show you ECT volts?
EDIT: I think the fuel trims you are looking at are both ST fuel trims. Though I'm not real familiar with the app. See if there is another PID that specifically lists LT.
With engine warm, and air intake off, there is a LOT of suction going through the iac air hole. (See pic). Is that right? It will barely run, surging up and down with the air intake off.
Yes, that is the air bypass to the IAC that is letting the engine breathe while the throttle plate is closed. IAC is controlling the airflow.
While the truck is stumbling, unplug your MAF sensor and see if anything changes.
Sounds like your IAC is moving the pintle in and out then. I would next consider the ECT sensor. Also, maybe take your MAF off and make sure you didn't accidentally break loose a side of one of the little resistors from the bars in there while you were cleaning it. With my eyes, I need a 10x loop to see it clearly. Will your tool show you MAF g/s and MAF volts? Will it show you ECT volts?
EDIT: I think the fuel trims you are looking at are both ST fuel trims. Though I'm not real familiar with the app. See if there is another PID that specifically lists LT.
Ok, good to know. In this pic, I changed the displays so they can be seen easier, but it doesn't keep track of highs and lows. I can do a graph on the short term FT, but there is no long term. I did add MAF gs, but there's not one for voltage or anything ECT other than the coolant temp reading. I checked the wires and resistor things as well for the maf, they still look good.
Yes, that is the air bypass to the IAC that is letting the engine breathe while the throttle plate is closed. IAC is controlling the airflow.
While the truck is stumbling, unplug your MAF sensor and see if anything changes.
Yep, if I have the air intake off and it's stumbling bad, if I unplug the MAF, it smoothes right out. I'm thinking I'm just going to raise the idle using the screw just a hair, maybe 700 or so.
Yes, that is the air bypass to the IAC that is letting the engine breathe while the throttle plate is closed. IAC is controlling the airflow.
While the truck is stumbling, unplug your MAF sensor and see if anything changes.
Yep, if I have the air intake off and it's stumbling bad, if I unplug the MAF, it smoothes right out. I'm thinking I'm just going to raise the idle using the screw just a hair, maybe 700 or so.
04-26-2018, 06:31 PM
