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IAC???

B

B.RAIDER

NAXJA Forum User
Location
Central Texas
Ok, I have a question about it.
All other sensors checked good as I have posted in my MAT thread.
Replaced:
MAT sensor
New o2 sensor
MAP checks out ok
No sign of exhaust leaks
TPS checks ot ok ...vehicle shifts fine....
IAC was tested with a IAC tester and showed to work. But would not bring it down to correct idlling rpms once it was run up to higher rpms.
I read somewheres on here that if you put something (plastic card or similar) on top of the IAC port on the TB to stop the air ... the engine should die. Mine keeps running.....
Or should I put the top back on the TB with it pluged up and test it that way.
There is no vacuum at that port( with the top air box still off). Does that signify the IAC is bad?(not allowing air in)...or the wireing is corrupt( if that be the case)? Remember I did a smoke test on the vacuum system ( mentioned in my other thread), so no leaks showed up in the vac system.
The idle is fine at start-up then it starts searching from 750- 1000 rpms then gradually goes up to 1250-1500 rpm once warm.
 
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"on top of the IAC port" meaning inside the TB or pulling the IAC off and putting a card over the opening in the side of the housing it was bolted over? The former I would agree, it should die. The latter, the idle should rev way up.
 
kastein said:
"on top of the IAC port" meaning inside the TB or pulling the IAC off and putting a card over the opening in the side of the housing it was bolted over? The former I would agree, it should die. The latter, the idle should rev way up.
Click to expand...
IAC still installed and still hooked to power..... "on top" of IAC port....
 
Did you remove the IAC and clean the TB housing and the pintle on the IAC? I use carb clean in the housing and a qtip until it comes out clean. I use a tooth brush on the IAC pintle.
 
old_man said:
Did you remove the IAC and clean the TB housing and the pintle on the IAC? I use carb clean in the housing and a qtip until it comes out clean. I use a tooth brush on the IAC pintle.
Click to expand...
Did all the cleaning. Just took the IAC out and checked it again with one of the "exercise" gadgets that my mechanic friend let me borrow to use. The IAC works back and fourth as it should.
I left it set in the all the way back position, installed it and left it unpluged, to see what happens. The rpms shot up to 2500 rpms upon start up. I cut the ignition off then went and pluged it back in and it started as it should with idle around 750-900 range. Then as before it starts searching for a sweet spot in the ideling then steadily climbs to 1250-1500 rpms and stays in that range.
I'm guessing the ECU is my next stop.............:banghead:
My guess is something "telling" the IAC to open prematurely upon warm up....but what?
Coolant sensor checks ok also....I didn't mention that one.
In my other thread (MAT???)...to save some from reading it all.... I smoke tested the vac system and nothing showed up there either.
 
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Pull the air tube and check the "base" idle setting. The adjustment wrench should be a 3/32 allen. Back the adjuster off until the throttle plate is fully closed and the adjuster is no longer acting upon it, then screw it back in until the throttle plate just begins to move and no more. Put the air tube back on and check the idle.

Also, have you checked the entire vacuum harness? They get real brittle and you could have cracks almost anywhere. And, along with the v/harness, have you checked the EGR system?
 
joe_peters said:
Pull the air tube and check the "base" idle setting. The adjustment wrench should be a 3/32 allen. Back the adjuster off until the throttle plate is fully closed and the adjuster is no longer acting upon it, then screw it back in until the throttle plate just begins to move and no more. Put the air tube back on and check the idle.

Also, have you checked the entire vacuum harness? They get real brittle and you could have cracks almost anywhere. And, along with the v/harness, have you checked the EGR system?
Click to expand...
I will try the adjustment........as it sits now, it (throttle plate) is completely closed..... it looks like.
The vacuum harness was checked via a vacuum smoke test at my freinds shop. We went over the vac systm with a fine tooth comb (under, over inside and out). We put so much smoke in the system it smoked out of where we had it hooked for ten minutes before we stared it again.... LOL.
 
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I use carb cleaner instead of smoke.
 
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have you torqued down the intake/exhaust manifold bolts?

have you looked at these threads for possible solutions?

http://naxja.org/forum/showthread.php?t=1007698&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=997335&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=905849&highlight=high+idle+renix


what finally got the high idle problem on my 89 under control was doing a top end cleaning(intake, head, valves) with seafoam, manually cleaning the throttle body and IAC, torqueing down the intake/exhaust manifold bolts, and the cleaning of all ground connections. on my 89 there was a single ground wire coming from the main wiring harness(huge wire loom going through the firewall to the fuse block) that was attached to the drivers side fender wall in front of the windshield washer fluid tank. cleaning this connection made a big difference.

have you checked/tested the ground to the tps? some people run a new ground dedicated for this.
 
old_man said:
I use carb cleaner instead of smoke.
Click to expand...

I'm a firm believer in the "stogie" test.

Fire up the stogie, get it going, take a good hit and without inhaling blow into an open vac hose. If you have a vac leak, it WILL show up. Cost, .99 to 5.99 (depending on the cigar), works for me everytime.
 
ParadiseXJ said:
I'm a firm believer in the "stogie" test.

Fire up the stogie, get it going, take a good hit and without inhaling blow into an open vac hose. If you have a vac leak, it WILL show up. Cost, .99 to 5.99 (depending on the cigar), works for me everytime.
Click to expand...

You have got to be kidding me...That simple? :doh:

You mean I didn't need to cause that small explosion in my garage when I tried to build my own smoke machine using an old expresso machine, mineral oil, and a regulated air brush compressor. :explosion

:worship: My hat off to you sir...
 
89xj said:
have you torqued down the intake/exhaust manifold bolts?

have you looked at these threads for possible solutions?

http://naxja.org/forum/showthread.php?t=1007698&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=997335&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=905849&highlight=high+idle+renix


what finally got the high idle problem on my 89 under control was doing a top end cleaning(intake, head, valves) with seafoam, manually cleaning the throttle body and IAC, torqueing down the intake/exhaust manifold bolts, and the cleaning of all ground connections. on my 89 there was a single ground wire coming from the main wiring harness(huge wire loom going through the firewall to the fuse block) that was attached to the drivers side fender wall in front of the windshield washer fluid tank. cleaning this connection made a big difference.

have you checked/tested the ground to the tps? some people run a new ground dedicated for this.
Click to expand...



89xj said:
have you torqued down the intake/exhaust manifold bolts?
Click to expand...
Not yet...don't have a universal joint to use with my 1/2 drive torque wrench.

89xj said:
have you looked at these threads for possible solutions?

http://naxja.org/forum/showthread.php?t=1007698&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=997335&highlight=high+idle+renix

http://naxja.org/forum/showthread.php?t=905849&highlight=high+idle+renix
Click to expand...
I had read two of the three......have already checked most, if not all of the stuff mentioned.
89xj said:
on my 89 there was a single ground wire coming from the main wiring harness(huge wire loom going through the firewall to the fuse block) that was attached to the drivers side fender wall in front of the windshield washer fluid tank. cleaning this connection made a big difference.
Click to expand...
I cleaned the C-101 plug this morning with contact cleaner and used dielectric grease when I put it back together.
No change..................
89xj said:
have you checked/tested the ground to the tps? some people run a new ground dedicated for this.
Click to expand...
Yes, the ground is good and TPS test and works as it should.
 
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