EGR/O2/Vacuum Problems?

[ZX6RArcher]

Hey guys-

First time poster here, but I've been an avid Bronco fan ever since my uncle had them (two of them). I loved how he could take the top off in the summer and how in the winters he could pretty much bully his way through anything with it.

So the need came where I need to tow my race bike to the track and I found a used 87 Bronco XLT for sale for $1000. The body was solid, the paint was iffy, and the interior wasn't too bad. I talked the guy down to $900 and drove away a happy camper. All I want to do is do the $50 paint job as seen online and maybe possibly a small body/suspension lift. So all in all, I'm happy. It's got the 302 EFI and the C6 auto tranny (rebuilt 20K miles ago).

So fast forward to now (2-3 weeks later) and I'm having a few issues with it. When I first start it, I let the idle calm down to under 1K RPMs. When I stick it reverse and drive away, the CEL comes on but goes away. At first I thought it was maybe a wiring issue, but I checked the wiring and all is good there and it comes on and goes away when I initially give it gas. After it warms up a bit, it very seldom comes on.

I went to O'Reilly's and bought an EEC scanner and it popped two codes; 41 and 33. I went out and bought a new EVP sensor and EGR valve just in case I needed them and started troubleshooting. I also picked up a vacuum pump to test vacuum lines. When I run a multimeter across the pins and move the plunger on the sensor it varies in resistance so that tells me it's running fine. When attaching a vacuum of 10" to the vacuum port on the EGR valve, the resistance varies, not a whole lot, but a little.

When I put 10" of vacuum on the EGR valve it holds the vacuum so it's telling me that the diaphragm is still good. But, when I apply vacuum I am not seeing the diaphragm move so maybe it's stuck? I can also put 10" of vacuum to it with the EVP sensor removed and it holds, then remove the cover from the top port and hear the air rush in and see some dust/gas/particles come out. So I'm wondering if possibly it isn't gunked up and stuck causing the EVP sensor to not move giving me the code 41 (EVP sensor closed).

I also tested the yellow vacuum line going to the EGR valve and I'm not getting any vacuum there with the engine running and under load (roughly 2K RPMs). So I started following that line and it looks as if it's disconnected. There is another yellow vacuum line that is sitting on top of the intake manifold that isn't attached so I'm thinking it's either that line or the line to my EGR valve. I'm guessing it's the line for the EGR valve since I'm not getting any vacuum on that line and when I try to apply a vacuum the gauge doesn't move at all like it's venting to the atmosphere. I've searched the forums and looked at the sticker on my intake box to look for the routing but I can't seem to find exactly what the EGR's vacuum port should be connected to.

So if anyone could, please let me know what the EGR valve should be attached to and attach pictures, I'd be grateful. The guy who had this before me disconnected a few things so I'm wondering if he didn't mess something up. The truck runs well, it's just the CEL that momentarily comes on time to time while driving and it seems like it idles a bit rough and every once in a while I get a power surge while just driving. So that's why I'm leaning towards and EGR issue and the possibility of the vacuum line being either defective or not attached to the proper vacuum source.

Also, could this issue be causing the issue with my O2 sensor running lean? Like if the exhaust gases aren't recirculating, could that cause the EEC-33 that popped up on my scanner? Any suggestions or personal experiences you guys have had would be greatly appreciated! Thanks in advance,

-Tony

 

[50joe]

I'm gonna go off the the top of my head with out checkin the schematic, so bear with me a bit. If the EGR is holding vacuum, do a engine running test. At idle, with vacuum applied to the egr, the engine should stumble or stall. If it does, you know the ports are clear. If not they are plugged, but that shouldn't trigger a code in a "stupid" computer system like we have. All the sensor on the EGR valve does is tell the computer weather or not the valve is open. You should not have vacuum to the egr at idle, or just reving the motor. Usually, an EGR only kicks in over a certain RPM under load, and/or under a long deceleration. The line to the valve,(red I think), should attach to a solenoid on the other end, which can either be controlled by another solenoid, or a ported vacuum switch(screwed into the intake). These older systems can be a pain in the ass, so a good manual with diagrams, and operations specifics are a big help to the backyard guy.