Leaky EGR Vacuum Modulator! HELP PLEASE!

Okay so last weekend, on the drive back down to Phoenix from Payson (bout 85 miles one way), my check engine light turned on. The steep uphills had my little 2RZ working exxxtra hard. I'm assuming that's part of the reason why the light turned on. So once I got back into town, I went to Autozone and had them hook up a scanner to my truck. Turned out to be a P0171 code; lean A/F ratio. Since then, I've replaced my upstream oxygen sensor and PCV valve. Light's still on though. So a couple hours ago I ran that smoke test to check for vacuum leaks and... there's a leak. It's coming from the EGR vacuum modulator. So I linked the intake back up, started the truck and decided to spray some starting fluid at the modulator, expecting to hear a change in idle speed but there was no change. I always thought if you spray starting fluid at a vacuum leak, idle speed would change.

So I guess what I'm asking is: should I spend $80 and buy a new modulator? And do you guys have any other suggestions for how to fix that P0171 code?

 

The scanner that read the code should be able to reset the light and erase the fault code. Also what is that setup you have in place of the intake tube?

 

Your MAF sensor needs to be in the intake stream to get the proper fuel mix.

 

Oh, that was for the smoke test. You basically seal up the intake somehow and blow smoke through it. It was only set up like that for about 30 minutes.

 

I "think" you can clean your egr. But dont quote me. Google it. If not. try a junkyard. Guaranteed it will be less than 80. We all know that risk. Is it the egr or just the gasket for said egr..? Something to check if you already haven't. Good luck and hope this helps. Just curious, how did you perform your leak test.

 

yes it can but they wont do it anymore, least not around here. maybe other states are different but around here they passed a law that said if they reset the code for you then they are responsible for the vehicle so their policy now is check and inform only and never reset anything. if you want to be able to reset it you have to buy your own scanner tool.

OP - just disconnect the battery for 30 minutes and that should reset the CEL but after doing this everything is reset so it will take about 200 miles or several start and stop cycles running around town for the ECM to adjust the air fuel mix for best performance so it may run rough at first after doing it and you will have to redo your radio presets.

also that modulator is designed to be open and under that round black cap is an air filter where it draws air in so just because you saw something doesn't mean its bad. look here: http://www.lexls.com/tutorials/emission/egrfilter.html

 

Got similar code, replaced the actual valve itself cause mine was excessive egr. Meaning valve had build up and wouldn't close. 600 miles later something else with the egr. Assuming now I have same issue you are with the modulator. Honestly it's only really effecting gas mileage.

 

Good question, I'll have to look again and see if that's what it is.

And there's a few ways you can do it, but I decided to blow smoke directly through the intake (helps if the throttle body is wedged open). I just removed the elbow hose connector, sealed up the end of the intake with duct tape, cut a small hole in the duct tape, stuck a funnel through the hole, stuck a small hose through the funnel, lit up a stogie and the rest is history.

 

Are you saying that the ECM will adjust to the lean A/F ratio OR that the ECM will adjust the A/F ratio to the correct ratio? Sorry, n00b here.

 

the ECM will adjust the A/F ratio to the correct ratio based on all the sensor readings it gets

 

this was really starting to go some where, and then

I am having similar issues and still need to know if the modulator should leak during a smoke test?

 

The EGR modulator is not airtight. You can pull that top cap off. You'll see a little filter. I would bet smoke would be able to come out of there while smoking it but I haven't smoked my intake before. Check it out and let us know what you think.

 

the modulator is vented to atmosphere. The lean code is a symptom. It could be as simple a a small exhaust leak.

I am curious, do you make this run often? The reason I am asking is that if it were me I would run the fuel tank until almost empty then fill up with Chevron gas and make the run and see if a gas with additives that runs cleaner "fixes" the problem. The high end imports I worked on back in the 80's had odd running issues after a while of around town driving and the fix was either dump some techron in the tank, take her on a long multi hundred mile trip or scrape the build up of crap off the intake valves.

 

Delete it