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EGR System Intermittent failure

2274 Views 2 Replies 3 Participants Last post by  crashq
Good weekend all.

My 1990 Pickup 3.0 L V6 3VZE is experiencing an intermittent problem with the EGR system (check engine code 71). The check engine light will turn on and off, often during highway drives several times. If it starts out with the light off, it may come on during the drive and if it starts out with the check engine light on, it may turn off during the drive...

Is there a part of the system would be most likely to fail occasionally? The valve itself? the temp sensor? the solenoid?

Any suggestions?

Thank you.
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It could be any one of those components that are failing. I would first start by checking for vacuum leaks to the hoses going to all the EGR valve components. If no leaks are found, check the EGR valve for sticking, there could be some carbon stuck up in there making the plunger get hung up. If you have a Haynes Repair Manual it will show you how to test all these components. Hope this helps.
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In addition to checking the components, you should check the wiring to the sensor that goes on the passenger side of the intake maniforld. I don't remember exacly where it goes in, but it is right ablove the middle cylinder on that bank near all of the vacuum hoses. (I will try to take a photo tomorrow.) The wires that come off this are very thin and easily damaged.

After having my heads replaced, I found that the mechanic yanked one of the wires (atteached tothe sensor) out of its connector and damaged the wire. I was doing a fair amount of city driving after the repair, so the engine didn't always get hot enough to trigger the EGR valve (it may take as much as 45 miles of driving to heat it up enough). The problem appeared to be intermittent. After fixing that problem, I also found that he had hooked up the vaccum lines to the wrong places despite the vacuum diagram being stuck on the underside of the hood). Both of these problems caused intermittent "Check Engine" lights. I eventually cut the damaged part of the wire off the sensor, and soldered a new wire on. The problem went away.
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