O2 Sensor, IAC or other? Another Low Rough Idle
05-25-2015, 10:48 PM
#16
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I drilled a 3/8" hole on each side of the CPS 
was i just supposed to drill one?
I think I left some grime on the sides by the connecting rod of the butterfly valve. i'll clean that up. I also noticed that the blade catches on something if i open it slightly.
I unplugged the line on the manifold that goes to the firewall side of the valve cover.
was i just supposed to drill one? I think I left some grime on the sides by the connecting rod of the butterfly valve. i'll clean that up. I also noticed that the blade catches on something if i open it slightly.
I unplugged the line on the manifold that goes to the firewall side of the valve cover.
One hole woulda been fine, but I'm thrilled to hear of the results of both holes!! LOL.
See my Tip 14 on the throttle butterfly adjustment procedure. Looking forward to your report back.
05-26-2015, 09:52 PM
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so here what i got... i cleaned up a little... it looked cleaner than I remember it.
ran the exact same after cleaning. just for fun, I opened up the TB a tad bit m
ore, still the same. watched IAC retract with key on and slowly close when started.
BTW got 35 psi on the rail and 40 with vacuum off.
05-26-2015, 10:05 PM
#18
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All that looks good to me.
05-27-2015, 01:45 PM
#19
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should the IAC be all the way closed when in idle? how does the ECU control the IAC? off of position/steps or off of an RPM reading? should I just start replacing sensors? why do I have 14 volts on my O2 sensor instead of 12?
05-27-2015, 04:39 PM
#20
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ECU targets an RPM.
Don't just replace sensors.
Because 14 volts is the battery voltage when you tested it.
05-30-2015, 03:55 PM
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some more things to lead me to an answer...
The idle seems to be okay in open loop. it takes a long time for the idle to drop it seems to happen the same time the engine heats up... if it shut it down and start it back up while it still hot, the idle drops fairly fast... I watched the IAC close up (but was still letting air through.
this leads me to believe that the problem is with the O2 sensor. but I am now clear on the duties of the O2, IAC, TPS CTS and MAT during open loop vs closed loop...
Can anyone enlighten me?
BTW I borrowed a friends MAP sensor, and no change so i'm pretty sure i can rule that out.
ACCOUNTABILITY: It really bugs me that people get help on this forum, but they don't bother to post their solutions when they find one. If someone runs into this months down the road and I haven't posted what fixed this issue, call me out!
The idle seems to be okay in open loop. it takes a long time for the idle to drop it seems to happen the same time the engine heats up... if it shut it down and start it back up while it still hot, the idle drops fairly fast... I watched the IAC close up (but was still letting air through.
this leads me to believe that the problem is with the O2 sensor. but I am now clear on the duties of the O2, IAC, TPS CTS and MAT during open loop vs closed loop...
Can anyone enlighten me?
BTW I borrowed a friends MAP sensor, and no change so i'm pretty sure i can rule that out.
ACCOUNTABILITY: It really bugs me that people get help on this forum, but they don't bother to post their solutions when they find one. If someone runs into this months down the road and I haven't posted what fixed this issue, call me out!
05-30-2015, 03:59 PM
#22
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some more things to lead me to an answer...
The idle seems to be okay in open loop. it takes a long time for the idle to drop it seems to happen the same time the engine heats up... if it shut it down and start it back up while it still hot, the idle drops fairly fast... I watched the IAC close up (but was still letting air through.
this leads me to believe that the problem is with the O2 sensor. but I am now clear on the duties of the O2, IAC, TPS CTS and MAT during open loop vs closed loop...
Can anyone enlighten me?
BTW I borrowed a friends MAP sensor, and no change so i'm pretty sure i can rule that out.
ACCOUNTABILITY: It really bugs me that people get help on this forum, but they don't bother to post their solutions when they find one. If someone runs into this months down the road and I haven't posted what fixed this issue, call me out!
The idle seems to be okay in open loop. it takes a long time for the idle to drop it seems to happen the same time the engine heats up... if it shut it down and start it back up while it still hot, the idle drops fairly fast... I watched the IAC close up (but was still letting air through.
this leads me to believe that the problem is with the O2 sensor. but I am now clear on the duties of the O2, IAC, TPS CTS and MAT during open loop vs closed loop...
Can anyone enlighten me?
BTW I borrowed a friends MAP sensor, and no change so i'm pretty sure i can rule that out.
ACCOUNTABILITY: It really bugs me that people get help on this forum, but they don't bother to post their solutions when they find one. If someone runs into this months down the road and I haven't posted what fixed this issue, call me out!
05-30-2015, 04:02 PM
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05-30-2015, 11:54 PM
#24
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05-31-2015, 02:22 AM
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I am curious as to what you end up finding. i have a 90 xj with the same issue..
also,
i have looked at 3 good running 90 xj's and they all have this issue. not sure why yet. there has to be something different between the 89 and 90's. i wonder if a earlier ecu would change anything.
also,
i have looked at 3 good running 90 xj's and they all have this issue. not sure why yet. there has to be something different between the 89 and 90's. i wonder if a earlier ecu would change anything.
05-31-2015, 08:11 AM
#26
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ECUs are pretty much the same.
On the driver's side of your throttle body is a tiny round metal plug.
It can be removed with an awl or pick by tapping one side of it in like when you remove a freeze plug.
Knock it out of there and tell me what you see. Be gentle with it.
On the driver's side of your throttle body is a tiny round metal plug.
It can be removed with an awl or pick by tapping one side of it in like when you remove a freeze plug.
Knock it out of there and tell me what you see. Be gentle with it.
06-01-2015, 11:19 PM
#28
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