UberNoob

air filter needs changing?

MotoEvo

iTrader: (3)

For the catalytic, the basics are a visual test to see if the honeycombs are clogged (you should be able to see light through the catalytic), and to tap it with a rubber mallet to see if any rattling can be heard. You can also check by using a vacuum gauge to measure the back pressure before and after the catalytic.

For the o2 sensors, you'll have to measure the voltage. I don't know if the GS is a wide band or narrow band sensor though. For a narrow band, you can try the following: http://mymiata.paladinmicro.com/Miata4-WireO2.htm
The how-to test is at the bottom of the page.

For a wide band, it's a bit easier; place it in a rag sprayed with brake cleaner. It should stay at full rich until the rag dries up. If it goes to lean before the rag dries up, it's a bad sensor.

If all those check out, I'd start looking at the vacuum lines to check for any cracks/leaks.

Anyway, good luck and hope you can get your mpg back!

sam12345

iTrader: (1)

Try this

https://www.clublexus.com/forums/ls4...-in-1-fix.html

whytry

iTrader: (1)

Any thought of maybe fuel filter needs changing? Any ideas. I've done some searching and it sounds like its not needed but still... I saw a DIY on it but I can't find it now. V

Also for checking O2 wouldn't a rag loaded with brake cleaner burn up on hot exhaust like the cat?

sam12345

iTrader: (1)

I think he means remove o2 sensor and measure with rag over it (rag over the part that is in the exhaust

whytry

iTrader: (1)

Oh I got it. That makes more sense. Thx bro

whytry

iTrader: (1)

Update - I went down and had my codes ran n it wasn't throwing any but the tech said it looks like I might have a 02 sensor going. He said it was displaying characteristics of being lazy on the readout n that could be part of the issue. So I replaced my 02 sensor 2 on bank's 1 and 2 per his recommendations. (Thx DIY). Been about 3 wks and now I am throwing codes. Here are the codes:


P0441
P0446
P0455 - evap
P2418 - evap control system bypass malfunction

They are all tied to the EVAP system in some way shape or form. Anybody have any ideas of what to check or where to go from here? I'm getting desperate... Please help.

Blanco

iTrader: (8)

Evap codes are usually legit. I know I had to replace some valve near the evap canister once. I think I may have had to replace the canister itself several years ago.

Don't recognize the first 2 codes, but that last one sounds like it could be pointing to the valve I'm speaking of. It's not too expensive, and could probably be an easy DIY.



Part 77740N in the diagram is the part I speak of. CL price is listed at $61 and change.

EDIT: That diagram is for a 98 GS400, don't know if it's the same for a 430, but you get the idea.

Just stumbled across this thread. Think it'll fix/answer all your problems.

98 GS300 P0441 & P0446 W/(Pic)

whytry

iTrader: (1)

Nice I will look at that

neegroy

iTrader: (19)

really does this come into play?

but yeah i dont remember ever seeing my car mpg at 19-20mpg lol fluttering around 13-15 LOL

JDRICHARTZ

I am having the same problem with my very low mileage (53,802 miles) 2002 SC430. About 1,500 miles back the check engine light came on. Showed one of the two front air-fuel sensors was bad. Had both replaced ... no change in mileage. I am thinking about using an ethanol treatment additive. Anyone have any experience or info about the latter?