EGR = lean codes?

[azaizai]

Quick question:

If my EGR valve had a crack at the base (just before where it threads onto the tube with the dpfe lines that connects to the manifold)...would it cause a dual lean code (p0171, p0174) and audible misfire @ low rpm idle?

I know that the DPFE is good (new from 6 mo's ago), the EVR is good (was bad, replaced...idle got a lot better, exhaust still sounds like a misfire) and if I remove the vacuum line from the top of the EGR and create my own vacuum...it will pull the engine down @ idle. Soooo I guess the EGR still functions.


My guess is that since the crack is below the diaphragm that the intake can pull the air through and lean itself out? Does that make sense?

 

[azaizai]

Quick addition:

Didnt mention that I have a 1997 Ford Ranger 4WD 5 speed with a 4.0 OHV

I tried the brake clean trick. I let the 4.0 reach a stable idle (it still rocked of course) and then sprayed brake clean below the EGR, directly at the crack. There was no change. I even tried lifting/pressing on the EGR and spraying thinking it might affect it, but it didnt.

I'm thinking perhaps I was wrong.

I found this through Google Images, it looks very similar to mine but in a slightly different configuration. The crack is very similar.

My exhaust sounds normal for a few seconds and then *poof* it'll release some exhaust after a half second pause. I think this is about the same time the engine rocks a little. Its not super loud or anything, but it makes a noise like the exhaust was trying to say "Puh". There's always a lil dribble of water coming from the tail pipe as well.

Quick history: I've just recently replaced the heads, head bolts and all gasket from the heads to the intake. My driver's side head and head gasket were both cracked. I torqued, checked and retorqued the intake bolts and they've stayed the same for several days now. I've tried spraying all the vacuum, and nothing bogs down.

I'm going to bring home a Volt/ohm meter tomorrow and try some component testing, I guess. The rocking motor (assumed misfire) condition existed before the recent heads/gaskets (I had milky oil and a galon of coolant missing).

 

[tdog]

your egr tube has a big O-ring on the top of it where it goes into the air plenumn that is prone to leaking , especially after any kind of work has been done to it. but if you have any kind of crack on your egr valve or egr tube i would recommend replacing them.

 

[azaizai]

Alrighty! I took off the upper/plastic intake this morning. Found that lil EGR O ring all warped and twisted up! Replaced the gasket So score one point there.

I also poked my head inside and didnt find any gaskets sticking out or visible fluid leakage. So there's another positive point.

I brought out all my gauges and stuff and tried checking all the sensor spec's
All of the intake sensors/IAC tested fine.

I also popped on a fuel pressure tester and checked it out.
I noticed my pressures were a lil low (35 psi with Key on, engine off and a lil below 30 at idle, with a jump back up to 35-36 with the FPR vacuum line off (and plugged))
Now I'm sure this is an OEM, 12 year old fuel pump...but are the pressures adequate? I know they're a lil low, but would that make the difference between lean banks 1 and 2 and not? I cleared the codes the other day and it took a few solid hours of driving before the codes came back on.

I also pulled the plugs and wires on a whim to see if anything obvious showed up.
1) One of the plugs (cylinder 3) had a burnt/brown substance on the insulator at the *wire* end. Like right near the hex part that you put the socket on. Only plug that looked that way. I also found that the wire going to 3 was loose at the plug. Looked inside and the metal part was spread out (didnt touch and make a cylinder...it just spread open like a 'V' until it turned the 90' to connect up to the wire.)
I tried pulling the wire from the coil and see if the engine ran any different.

Well...it ran about the same all the way to low idle, but then it seemed worse...but not *that* much worse. So I'm gonna see what new plugs/wires do for me, I guess.

any thoughts on the fuel pressure? Do ya agree that the burnt stuff @ the spark plug was from the loose wire. I know this is a lot of crap to read, so thanks in advance!

 

[azaizai]

Hmmm...more fun news:

1) got a can of seafoam with my plugs/wires. Put 50% in the tank, and ran 50% thru the brake booster line. Had pretty typical results...lotsa smoke @ the tail pipe (with the lil miss, the pipe was actually blowing smoke rings every once and a while, which was cool). But...as I went to the engine bay, drivers side, I found a tiny lil wisp of smoke from the end of the manifold. I dont know if it was from the EGR tube join or from the connection to the Y-pipe...but there was definitely smoke flowing from down there. From underneath, if I blew on the y-pipe:manifold connection...more smoke would appear from the bottom of hte join. I didnt take this apart when I pulled the heads (those bolts were scary)...so I'm not sure if I did it, or it was always there...hooray.

2) I think I created an oil leak lol. I was reaching around behind the heads near the firewall to see if I could find any loose oil leaking down the backside. Ya see...I got the new fel-pro lower intake gaskets...and I forgot to put the two lines of RTV to seal the valley. I didnt have a leak when I put my hand back there..nothing on the pan or bellhousing.
So I drive to O'Reillys to get the plugs...pulling out of the lot I see a lil spot underneath my truck. Finger it up, its oil. Look underneath...and I've got oil all over the place..doesnt drip a whole lot...but its enough.
So I guess I'm replacing intake gaskets again. :/ I bet that might affect my lean condition too, right?

 

[azaizai]

Well, replaced the lower intake gasket (got the 1 piece gasket this time!), replaced the fuel rail gasket (valve cover gaskets came with a new one, different design...figured why not?), and the plugs and wires then put it all together. Let it idle and everything's back to where we started.

The check engine light came on after about a half hour of driving (less than 50 miles, I'd imagine) and it still has the low idle misfire/lope. No white smoke or sweet smell from the exhaust.

Soooo...I'm thinking I need to work on the exhaust/EGR tube and see if i can get that sealed up (thinking thermosteel for now...then maybe attack it with a torch and some elbow grease when I can get to it). I still need to test the O2 sensors as well. Bah!