Won't idle, but............
10-17-12, 12:42 PM
#1
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Won't idle, but............
My 400 won't idle for some reason, but if you just slightly touch the throttle a TINY BIT, it runs like a top and there are zero issues. It seems like the idle has just dropped slightly below where it needs to be to maintain the car running. A minuscule increment of throttle and the world is a happy place.
I popped the throttle cover plate off and changed the position of the idle set screw on the throttle plate and BAM the world was all perfect again.
Now, something went wrong. Something changed. Something needs fixed. What could it be?
I checked my vac lines........ all good. Unplugged the TPS and the car got much worse so that is working. Unplugged the MAF with the same results so it is working. I have the PS pump bypass mod I came up with years back and posted here so no PS fluid issues or vac issues thereof. As long as that idle plate screw is up a little bit changing the idle position (NOT THE ACTUAL RPM, just the throttle position) then I have no issues. It actually still idles at the perfect rpm, I did not change the RPM by adjusting the throttle up that is what is weird.
Running out of ideas........... If you got in this car and drove it off you'd have no idea I had to adjust the set screw on the throttle plate, it runs like a top.... idles at 700 or so.
I popped the throttle cover plate off and changed the position of the idle set screw on the throttle plate and BAM the world was all perfect again.
Now, something went wrong. Something changed. Something needs fixed. What could it be?
I checked my vac lines........ all good. Unplugged the TPS and the car got much worse so that is working. Unplugged the MAF with the same results so it is working. I have the PS pump bypass mod I came up with years back and posted here so no PS fluid issues or vac issues thereof. As long as that idle plate screw is up a little bit changing the idle position (NOT THE ACTUAL RPM, just the throttle position) then I have no issues. It actually still idles at the perfect rpm, I did not change the RPM by adjusting the throttle up that is what is weird.
Running out of ideas........... If you got in this car and drove it off you'd have no idea I had to adjust the set screw on the throttle plate, it runs like a top.... idles at 700 or so.
10-17-12, 12:46 PM
#2
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Forgot to make a list..........
~ fuel pump and ECU are fine, car runs perfect
~ vac lines are checked
~ MAF and TPS checked
~ intake checked for fluid and blockages
~even after turning idle set screw up car still idles dead on 700 rpm where it should
It just acts like the throttle was low, everything else is well.... I know that points to TPS, but it checked out on ohms test and unplugging makes a huge difference. You would never know that I had to do this earlier to make it run if you drove it right now, but the question I need to know is WHY. Something needs fixed.
~ fuel pump and ECU are fine, car runs perfect
~ vac lines are checked
~ MAF and TPS checked
~ intake checked for fluid and blockages
~even after turning idle set screw up car still idles dead on 700 rpm where it should
It just acts like the throttle was low, everything else is well.... I know that points to TPS, but it checked out on ohms test and unplugging makes a huge difference. You would never know that I had to do this earlier to make it run if you drove it right now, but the question I need to know is WHY. Something needs fixed.
10-17-12, 03:55 PM
#3
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And after 30 miles whatever was screwed up unscrewed up and the idle speed shot up to 3000 which was the amount I had set the idle screw up to get it to idle normally. Now I had to set the idle screw back to it's original position and everything is back to where it was............. at this moment. So a vac line can't fix itself, a fluid line could have gotten a clog, but if it does it again we'll know it is electrical in some way.
10-17-12, 04:44 PM
#4
10-17-12, 08:18 PM
#5
Crap, I forgot to check for codes that didn't illuminate the CEL before ordering a new IAC for my car.
I have the classic "revs to 3k, drops, repeats" issue though and the TPS checks out with the meter so I'm still leaning toward IAC for me.
Your TPS check included the idle switch, right? That's separate from the variable resistance of the TPS terminals. Just covering the basics...
I have the classic "revs to 3k, drops, repeats" issue though and the TPS checks out with the meter so I'm still leaning toward IAC for me.
Your TPS check included the idle switch, right? That's separate from the variable resistance of the TPS terminals. Just covering the basics...
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10-18-12, 05:34 AM
#8
1JZ Single SC400
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Codes are:
24- Intake air sensor. Built in to the MAF. This keeps the intake air sensor at 68 degrees if this code is tripped.
21- Main 02 sensor, either left or right one...
Code 31- Air flow meter (MAF)... Again if the computer is reading this code, it is in the fail safe mode. NO air is being measured to the ECU for 2 seconds above 300 rpm. Second thing is engine stall. Check voltage at MAF, and if good, check ECU...
I have the PDF file, this is directly from that... Good luck..
10-18-12, 07:15 AM
#10
Just a small thing to check: The throttle drive line cable, the one above the throttle body/TPS. Mine was running really rough but when I tightened the loose throttle cable, to fixed it in an instant. Though. you have codes that say otherwise...I'd just peek a look at that...
10-18-12, 01:45 PM
#12
I have seen it both ways, the o2 causing the maf code and the maf causing the o2 code. since you have the IAT code in addition to the maf code, I would first look at the maf and it may solve your o2 code. those circuits may also share the same engine ground, so take a glance for pinched wires on those connectors.
10-20-12, 08:38 AM
#14
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It came back last night. I have a spare MAF I'm gonna swap this morning and see what it does. The issue is that since I am the one who unplugged the maf and tps to see if it made a difference I may be the source of those codes.
Many thanks!
Many thanks!
