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won't pass smog

2653 Views 3 Replies 2 Participants Last post by  rlg4675
Hello , I've got a 1989 Totota 4 runner w/ the 3.0L V6 w/ a 5 speed and 270000 mi on the clock. The truck runs great but when I took it in for a smog test, the fast idle was too erraticand the truck would not hold the fast idle for the test. The idle surges at anything above 2000 - 3000 rpm when cold and 1500 -3000 when warm. the truck runs fine and will rev up just fine, but if you rev it slowly it surges at 1500 - 2900 rpm and then will rev up from there till red line.I cant find a vac leak any place,the air box has been replaced with a K & N unit. I am stumped the coil looks fine and the distributor has no excessive free play . The cap and rotor are new. Any Ideas are welcome.
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smog problem

The problem is that I can not hold a high idle , the rpm wil surge between 1200 - 2700 rpm and the smog tech can not get the rpm to hold steady. The smog equipment will not register and will kick off and not let the test go on. I cant find a vac leak and the truck will hold a steady cold high idle , but will surge if taken from the cold high idle (about 1500 rpm) to 2700 rpm .Might this be the tps ? Any help is welcome.
If fuel injected, check the IAC valve. This valve allows a small amount of additional air (or less) into the engine to stabilize the idle. Normally it is located on the throttle body, it could be sticking. Check this first. And check the MAP sensor. You can try cleaning these with Seafoam or something similar. Might be a fuel system problem, fuel pressure, etc.

Thank You for the suggestion to check the IAC valve .I will also try to clean the MAP sensor tonight when I get off work, again thank you so much.

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