First Post! New FZJ80 Owner... Looking for some expert idle advice! (1 Viewer)

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I’ve literally been chasing the SAME EXACT THING for months now and yes, my TPS is set up correctly and I used OEM vacuum lines, new throttle cable and intake tube, etc. and although every step taken did reduce the idle, it’s still around 1k. It always had the high idle since I got it and it passed emissions previously and now won’t, at this point it idles too high to start the emissions test at some places and won’t Pass emissions because of really high HC’s (High CO as well) and now it throws a code 26. Again, everything I’ve done so far reduced the idle a little and it originally did not have a CEL, then went to throwing a code 25/26 combo and after the valve cover gasket and everything from the PCV valve to brake booster hose. I’m going to start just replacing stuff like the Fuel Pressure regulator (my vacuum line seems plugged on it?) and possibly the EGR valve at this point. Would pin holes by the o2 sensor cause a vacuum leak because that’s what all signs point to?
 
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I’ve literally been chasing the SAME EXACT THING for months now and yes, my TPS is set up correctly and I used OEM vacuum lines, new throttle cable and intake tube, etc. and although every step taken did reduce the idle, it’s still around 1k. It always had the high idle since I got it and it passed emissions previously and now won’t, at this point it idles too high to start the emissions test at some places and won’t Pass emissions because of really high HC’s (High CO as well) and now it throws a code 26. Again, everything I’ve done so far reduced the idle a little and it originally did not have a CEL, then went to throwing a code 25/26 combo and after the valve cover gasket and everything from the PCV valve to brake booster hose. I’m going to start just replacing stuff like the Fuel Pressure regulator (my vacuum line seems plugged on it?) and possibly the EGR valve at this point. Would pin holes by the o2 sensor cause a vacuum leak because that’s what all signs point to?
O2 sensor shouldn't have ANY air leaks or the reading would be off and affect idle. Have it welded to seal any leaks.
 
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If I remember right, replacing the EFI relay kept mine from continuing the stalling out at the light symptoms and no-starts from happening but did nothing to fix the idle
 
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O2 sensor shouldn't have ANY air leaks or the reading would be off and affect idle. Have it welded to seal any leaks.
That statement scares me because my exhaust is pretty rusted, my o2 sensors test fine but when I eventually need to replace them, those things aren’t coming out due to the rust so I’m thinking I may eventually have to relocate to the PAIR valve exhaust ports. What really sucks is I had a set of new o2 sensors that I sold a few months ago because mine tested good, which I could have used to test this out (my uncle gave them to me, he had a NOS set from back in the day just sitting in the garage from an old 80 project).
 
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Did you clean your throttle body when you had it off? I mean did you clean all the carbon out and did you clean the edge of the throttle plate also? Carbon on the edge causes plate to be open more driving up idle. IAC has a harder time controlling idle because of this.
Doing this really helped with my high start-up idle and also helped with warmed up high idle as it returned it to 650. I also cleaned the IAC and reset the TPS.
 
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Dayton, OH
Also, that screw you were messing with is a dashpot. It keeps the throttle plate from slamming shut when you let off the gas abruptly.
Yeah that's kind've what I figured. On startup then, is it normal for the plunger to suck all the way in? The screw should/ or shouldn't be resting against it at idle?

Hopefully getting some help adjusting the TPS the right way per the FSM this week. Unfortunately, I don't have access to a multimeter myself or anything at the moment. Really hoping that will help clear some things up.
 
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Did you clean your throttle body when you had it off? I mean did you clean all the carbon out and did you clean the edge of the throttle plate also? Carbon on the edge causes plate to be open more driving up idle. IAC has a harder time controlling idle because of this.
Doing this really helped with my high start-up idle and also helped with warmed up high idle as it returned it to 650. I also cleaned the IAC and reset the TPS.
I did clean the throttle body when I had it off. When I was done I didn't see any more buildup or grime if I recall. I did clean the hell out of the IAC when I had it off, too. Really hoping that itself isn't bad because I know they are decently costly. Hopefully after I get the TPS set here this week It will point me in a better direction.
 
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Zjohnsonua

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A few things... the 1FZ is modern for its day, but it's a basic EFI system, thankfully. It makes these issues less complicated.

The exhaust leaks are a red herring. Exhaust will be under a slight pressure, thus leaking out, not pulling air in. O2s can cause oddites, but I don't think that's where your issue is.

When everything is right, the ECM sets idle speed and will try to bring it to a few set points depending on gear selection, A/C commands, etc. In short, this isn't a carb, don't treat it like one. Back that dashpot screw off until it just does touch. The FSM has the specs if you want them.

The TPS and MAF are not trivial. When they're out-of-spec, all bets are off. Confirm that they're doing their jobs correctly.

But, what you're describing is reeking of a vacuum leak or IAC prob. The IAC's phenolic needle and the bore it fits into needs to be smooth and have no irregularities (the IAC needs to be able to drive all the way into that boss and make a seal if the ECM commands it). The o-ring around the IAC should be replaced or, if in a pinch, RTV'd to make a seal. Any rubber or relating interface where a seal is formed from the MAF through to the throttle plate is suspect. There aren't many places for failure, you'll find it.

Best of luck. Welcome to Mud.
 
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For what its worth, I have similar issue after buying my cruiser. It ended up being the TPS, however I also did the IAC at the same time just to hedge my bets.
No issue over a year later.
 

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