Check engine light only after driving on highway?

[WisconsinMonSTAR]

Hey guys, so my check engine light only turns on when I drive at highway speeds after about 20 minutes. If I leave my car off for a while, it turns off and doesn't turn on unless I drive on the highway for about 20 minutes. My car is running a little rich, not enough to put out any black smoke but it does smell a little gassy sometimes, but not always. Anyone know why it would do that? My transmission speed sensor is a little off, so my speedometer reads about 15 mph faster than what I'm actually going. I don't know if that plays a factor. Any input is greatly appreciated! Thanks guys/gals!

 

[92AWDHX40]

Can you pull a code.

 

[WisconsinMonSTAR]

Oh and sorry I forgot to mention, but my car is a 1998 gsx 5 speed.

I also notice a low whistling sound when my turbo kicks in. Does that indicate a boost leak?

O'Reilly pulled a high idle code. My car idles between 700-1k depending on the circumstances. My trusted mechanic said it was a running rich code

 

[92AWDHX40]

Do a boost leak to see if you have any leaks that should be done first.

 

[WisconsinMonSTAR]

I don't have a boost leak tester is there any diy ways?

 

[Sychotix]

I don't have a boost leak tester is there any diy ways?

All you have to do is spray some carb cleaner around any gaskets and vacuum lines while the motor is running. If the motor revs anytime your spraying then that's a leak.

 

[Archer Fabrications]

I don't have a boost leak tester is there any diy ways?

Yes go to the hardware store and make one.

Pvc cap same size as your turbo inlet, tire stem, coupler and clamps.

 

[WisconsinMonSTAR]

I just pulled the code P0170 fuel bank 1 code. Does that mean o2 sensor?

 

[Breezio69]

Its most likely an o2 sensor, mine threw that same code when I bought it and that was the fix.

Also, don't listen to sychotix, that's NOT how you do a boost leak test...

There are miles and miles of descriptions on how to properly do one, so I won't get into that, but I will tell you that its not "spraying down your motor with carb cleaner till it revs." if you had a boost leak large enough for that theory to work your car probably wouldn't be running at all.

 

[ohlegend]

I pulled this from another site: "It means your FI system is running either too lean or too rich and the computer can no longer compensate for the problem. You will have to figure out which way it is running and examine the possible problems. On most cars, the MAF is at fault, or the fuel pressure regulator."
They also mentioned a bad O2 sensor and vacuum leaks. I would check for a boost/vac leak first.

(In regards to CEL P0170)

 

[DSM1G90]

Spray thing works good in testing vacuum leaks not boost leaks.

 

[shakeandbake]

Dont blame a o2 sensor for doing its job. You most likely have a small leak that overtime causes the fuel trim to mess up. I had the same thing and it was an old vacuum line that would run a code after some 55+ mph driving.

 

[WisconsinMonSTAR]

I had my mechanic do a vacuum leak test, no leaks. He told me that based on the circumstances, it is likely the upstream o2 sensor. I'll be replacing it tomorrow and see how things go. I'll also be making a boost leak tester sometime this weekend. I think I may have a small boost leak near my bov. It is stock and has a plastic connector that was used because the old one broke. I'll keep you guys updated

 

[WisconsinMonSTAR]

Upstream o2 sensor replaced and the problem has been resolved. Nice and simple!