New here, quick question on possible lean issue

[adamsbomb]

Hey all, new to the forums. Quick question, just got an 87 turbo, car runs great, no hesitation or stalling issues. Temp guage runs in the normal range (despite having been low on coolant when I got it). Car has minor mods, it does have an air/fuel guage, thing is it always reads all the way lean, but I think it is broken or possibly hooked up wrong, wouldn't the temps rise on the temp guage if it were at 16 to 1 or whatever it is. Is there another way to check for lean condition outside of running it to a shop. Also, where is the mixture guage typically hooked up to?
Thanks in advance.

[jfunez]

it uses a wide band or lowband O2 sensor that reads of of the exhaust, tipically located as near or close to trhe turbo elbow...

[suprra_girl]

the gauge that you have is more than likely running off the stock 02 sensor and it is more than likey faulty

you can buy a real one (be prepared to fork out some $$ tho) at www.zeitronix.com

i wouldn't stress too hard about it... anything else which makes you think you're running lean?

[adamsbomb]

Oh, lol, sorry it failed the emissions test very high for nox which I guess can be an indicator of high combustion chamber temps. The car was low on coolant though. I have since refilled it and all is well there , no leakage or loss. It has a manual boost controller, changing the settings does nothing to change the lean condition of the guage though and the car doesn't and didnt get hot on the temp guage though.

[adamsbomb]

Another quick question, should there be a pre-cat on the downpipe?

[mrnickleye]

[QUOTE=adamsbomb]Oh, lol, sorry it failed the emissions test very high for nox which I guess can be an indicator of high combustion chamber temps. QUOTE]

High NOx is an indication that the EGR system is not working properly. Very possible that the vacuum hoses aren't hooked up properly, or the passages are plugged with carbon, and not allowing exhaust gasses to flow into the intake to control the NOx.

The EGR valves are very tough, and usually don't go bad. They could be plugged up with carbon. The transducer (back-pressure sensor) above the valve does go bad.

You can check some of this out yourself by un-plugging the vacuum hose to the EGR valve while the engine is idling, and use a longer piece of vacuum hose (keep it in your toolbox for future uses) to plug onto the EGR and suck on it with your mouth.

If the EGR valve is working, and the passages aren't plugged, the engine idle will fall right off, and possible kill the motor. If this happens, then your transducer is likely bad. Dealer only part.

If you can't hold the vacuum with your mouth (cause air comes thru) then the valve diaphram is bad, and the valve won't open.

If the idle does not fall off, and the valve seems to hold vacuum, (suck and release quickly with your finger on the valve, you should feel it snap shut), then you can remove the metal tube from the valve to the intake manifold, then try testing again. If you get loud exhaust coming out of the valve, then the passages are plugged in the intake manifold, and must be cleaned out.

The passages may be plugged before the valve, in the EGR cooler. Hope not, as it will be a bitch to remove the cooler and clean it out. Check by removing the EGR valve and starting the motor to hear if exhaust comes out the hole.

[IHateHacks]

"should there be a pre-cat on the downpipe?"

Yep.

But like Mr.nickleye said, if the EGR valve and vacuum modulator is working, your EGR passages are more than likely clogged or restricted by carbon, therefore causing your high oxides of nitrogen readings.