Trailsman1948

Any thoughts. A new engine (5k), super clean smog results at 2500 rpm but way off at idle. Starts fine, hot or cold, idles fine, runs fine shows no symtoms of anything being wrong. My A/F guage shows super lean at 1000 rpm idle, but after about 5 secs idling it drops to about 700 rpm and then shows slightly rich.
Thanks,Peter.

adam c

iTrader: (2)

Adjust your idle to 900-950 rpm for the test. It should pass. Anything under 1000 rpm is legal for the test in CA.

If you don't already know, the idle adjustment screw is recessed on the drivers side of the throttle body, under the intake elbow. Use a small mirror to see it for the first time.

BigWillieStyles

my car runs rich too, i was under the assumption that these cars were to run on the slightly lean side.

Trailsman1948

Thanks, for the info. So it just might be the fuel map goes rich under, say, 900 rpm and I shouldn't have an idle that low anyway?
Peter

jeff p

is your air pump working?

Jeff

Gadd

How about some more info on the car? OEM or aftermarket ECU, fuel pump, cat. ect?

Paul

Trailsman1948

Yep the air pump is there and working. The car does have an M2 upgraded fuel map to match J-spec turbos, XSPower intercooler and Racing Beat exaust, but on the A/F only shows rich on boost and then this low prm idle.
So this doesn't sound like an O2 sensor or something like that?
Thanks, Peter.

Gadd

Are you reading the A/F from a wideband? If you are you should be about 17 at idle with the A/P running. If your using a gauge that's reading the stock O2 sensor, thats useless.

I'd check the throttle position sensor, and then the intake air temp sensor.

Trailsman1948

The A/F is a (useless) narrow band, with funny little red and green lights and not numbers, so I just use it for relative measures rather than absolute. You mentioned the intake air temp sensor but wouldn't that effect the complete rev range rather than just beneath 1000 rmp?
Peter.

Gadd

Yes, but the effect may be exaggerated at idle. But simple stuff first, confirm the airpump is running at idle, check the TPS, and I'm assuming the plugs are new/good shape.

Trailsman1948

So is it common for the TPS go out wack? And should my idle be set as low as 600 rpm anyway?

Thanks, Peter

Gadd

Common, not necessarily. But if it's only slightly out of range, the car will not idle properly and it's easy to check . 600 is to low, it should 720/750ish. with out any accessory on.

Paul

Trailsman1948

It idles perfectly, runs perfectly, its 2500 smog test is squeaky clean. I'll try bringing the idle up to 800/900 rpm range and see if the A/F meter keeps showing the super lean reading it shows at 1000 rpm. Maybe this could just be the fuel map because this car run so well.. except for this part of the smog test!!!
Thanks, Peter.