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That ^%$%# Check Engine Light!


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Like a lot of you I have had an onging fight with my Check Engine light on my 91 LS 400. It reads out to be my egr, but that is not much of a help.. I have posted on this before. Well the thing is again back on.

So I checke vacum lines. All checked OK no leaks. Replaced the fielter in the egr Vacum Mod. And as it was only 4 bucks put in a new PCV valve. Still the dam light is on.

Last time I had a fight with this I did all the above and put a new gas cap on. Light would go one and off depending on the fuel level in the tank. After I desided to live with it. It started to work right.

On getting gas at this time I am not getting that "hiising" sound on "poping" the gas cap open. I doubt it is a bad gas cap as the "new" one is only about 1 1/2 years old. Any ideas on what or why no vacum on gas tank?????

Thank you.

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Just making sure you are "resetting" your CEL after performing your repairs.... I am not god with the gas tank sounds though.

I forgot to state that I did reset the the computer. I know some do it by pulling thefuse, but I find it a lot easer to just pull the + battery cable for 5 to 10 min.

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OK now an update.

I desided to try a cheep fix. I bought a new gas cap at AutoZone. For $8.00.

I know have vacum in the tank, and that sound when you open the gas cap.

I reset the CPU etc. Check eng light is off... For now. Only been about 20 miles of driving. We will see.

I know I can replace the gaskit on the factory cap... But the gasket from Lexus is $10.00 Cheeper to buy a after market gas cap.

I did not think it would be the gas cap, as the "old" one was under 2 years old.

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So you saved 2 dollars by going aftermarket? Twice?


Part of the scheduled maintenance for these cars is inspection and replacement of the sealing ring on the gas cap. The EGR system must have a vacuum in the tank to operate correctly (for capturing loose hydrocarbons before they get into the air).

Therefore if you don't have the hiss (the inrush of air into the tank) when you remove the gas cap then you have one very easy and cheap fix due.

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