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hey group, im hoping someone has some insight to my problem with my 91 sentra. I am overdue on my registration because I need a smog check,however, my engine light stays on althought there is nothing wrong with my car. it does go off at times but im never near the smog station when it does.I m trying to avoid a big fee in getting it checked out when it possibly could be somethin as simple as tightening a screw underneath my car .Im hoping someone has some insight on this problem.I need help asap thanks for listening .I am in the bay area california ,san jose if anyone is from here and knows a good reliable trustworthy mechanic
 

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Wise Cracker
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boomernook said:
hey group, im hoping someone has some insight to my problem with my 91 sentra. I am overdue on my registration because I need a smog check,however, my engine light stays on althought there is nothing wrong with my car. it does go off at times but im never near the smog station when it does.I m trying to avoid a big fee in getting it checked out when it possibly could be somethin as simple as tightening a screw underneath my car .Im hoping someone has some insight on this problem.I need help asap thanks for listening .I am in the bay area california ,san jose if anyone is from here and knows a good reliable trustworthy mechanic
You need to figure out why the light is on to diagnose the problem. The ECU has a self diagnosis mode where it flashes and based on the number of flashes you can tell what error code is being sent. You should search the forums for this as it is explained, you can also find a list of the codes and what they mean.
 

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Da Dirty South
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Check engine light

It could possibly be your EGR valve. My light used to flash ,but then about 6 months ago it stayed on. I got it hooked up to a scanner and reported a EGR flow interrupt. Thankfully where I live, I don't have to worry about Smog Control.
 

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boomernook said:
hey group, im hoping someone has some insight to my problem with my 91 sentra. I am overdue on my registration because I need a smog check,however, my engine light stays on althought there is nothing wrong with my car. it does go off at times but im never near the smog station when it does.I m trying to avoid a big fee in getting it checked out when it possibly could be somethin as simple as tightening a screw underneath my car .Im hoping someone has some insight on this problem.I need help asap thanks for listening .I am in the bay area california ,san jose if anyone is from here and knows a good reliable trustworthy mechanic

Damn Boomer!! I thought I made a post about my car and didn't know it! LOL I'm doing the same thing right now.
 

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I just checked my ECU thanks to NOSTRODOMAS' advice, and sho nuff...code 0302..."EGR control valve does not operate" Gotta check for prices now.
 

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Before replacing, check all the vacuum hoses associated with egr for leaks. The egr valve is about $100 and the backpressure transducer (bpt) is about $50. Also, if all the hoses are ok, I'd remove the egr valve and bpt and clean em up. By doing these two things, I was able to clear my check engine light for less than $10 in vacuum hose. Just a thought.
 

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Do we have two EGR valves? I'm looking at the diagram (from the Haynes manual I think) and it shows an EGR valve at the end of the throttle body arm where the intake arm starts, and an EGR valve & EVAP canister either on the throttle body itself or just underneath it. If there are two, then how can we tell which one is jacked up? I will go look under the hood and double check.
 

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2HunKris said:
Do we have two EGR valves? I'm looking at the diagram (from the Haynes manual I think) and it shows an EGR valve at the end of the throttle body arm where the intake arm starts, and an EGR valve & EVAP canister either on the throttle body itself or just underneath it. If there are two, then how can we tell which one is jacked up? I will go look under the hood and double check.
It's not really two egr valves, the second is more like a vacuum actuator that is based on exhaust backpressure. As you look at the engine bay from the driver's side, the egr valve is to the left and the bpt is to the right. Follow the metal egr pipe from the header to the actual egr valve. This has one pipe threaded onto it, one vacuum hose at the top, one rubber hose going to the bpt and two bolts and washers holding it to the intake. This comes off pretty easy and can be cleaned up with a little carb cleaner. Move the poppet around inside and make sure it's moving freely.

The bpt has the rubber hose from the egr valve at the bottom and two vacuum hose connecting to an elbow on top. Remove these and the two philips screws on the top and it'll come right out. Clean this up (do not use carb cleaner since it is not good for the rubber diaphragm inside) and use a piece of vacuum hose and mouth suction to verify the diaphragm is still sealed and actuates properly.

Put everything back together with new hose (about $7 at autozone), clear your check engine light, cross your fingers and drive around for a while. My light used to come on most often in cruise at highway speeds.

Hope this works, sorry for the long post.
 

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No, dude. that's fine. Thanx. Yesterday, I never turned the car back on after I reset the ECU. This morning, (Had to work) just hopped in and drove. No check engine light. Just now after work I tried to run my ass to the Smog Station before it came back on LOL!! But I got dinged for the Ebay air filter. So tomorrow I will run to the junk yard to get a stock one, and try to do what you suggested with the hoses. I hope it will work. My idle is a little off. I advanced it a little so the car won't die at intersections. But we'll see. I should change the damn oil too.
 
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