Reinhart, if you have any links which contradict what I've stated, I'd honestly appreciate being corrected.
When you didn't supply anything new to the most polite request possible for further information, I looked into it myself. I discovered information which appeared to back up your earlier statements, and readily posted it all for everyone to see. What more was I expected to do?
Stayed in open loop for a long time. Longer than a 4 cylinder. Then was popping in and out of closed loop a lot, then settled down. Again 4 cylinders running good don't do this. At least I haven't seen it.
I'd be suspicious of the thermostat. Put in a quality Stant SuperStat 195° thermostat... part number 45819.
Is it possible to post a picture or video of this occurring? It would be interesting to see exactly what this looks like.
Eveything is put away for the night. It was spewing smoke from under the flying saucer. Basically where the diaphragm is. Reading up on EGR Valves. If they have a Vac leak they get stuck open and it...kills your gas mileage, makes the car run like poop, along with having a vac leak.
Today I changed plugs, wires, coil, dis cap, and rotor, O2 sensor. Runs stronger, much less stumble, but I still have that backfire hesitation at low speed under load. I'm assuming EGR will fix that.
It was spewing smoke from under the flying saucer. Basically where the diaphragm is.
Ah, so it was actually the EGR valve diaphragm, and not the EGR valve itself that was leaking.
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Originally posted by Curlrup:
Reading up on EGR Valves. If they have a Vac leak they get stuck open...
There are positive and there are negative backpressure EGR valves. They react in a different manner. I forget which ones are factory installed on the 2.8 engine.
[This message has been edited by Patrick (edited 04-04-2021).]
The big black 1/2 inch ish hard tube coming out of the driver's side of the intake manifold to the throttle body by the IAC.... what is that? Leaking like mad with the smoke machine on. Right at the manifold.
Also it could be stuck open because of a faulty diaphragm. Which is an even bigger vac leak, and explains the bad gas mileage.
I believe with a faulty diaphragm the factory 2.8 EGR valve wouldn't be opening. That doesn't mean though that the valve is necessarily sealing exhaust gases properly.... but I think you found the major source of your vacuum leak below.
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Originally posted by Curlrup:
The big black 1/2 inch ish hard tube coming out of the driver's side of the intake manifold to the throttle body by the IAC.... what is that? Leaking like mad with the smoke machine on. Right at the manifold.
That's the tube that supplies air from the IAC valve. If it's not attached snugly onto the manifold or into the back of the TB, there'll definitely be a huge vacuum leak!
I'm surprised you hadn't reported issues with an excessively high idle speed.
[This message has been edited by Patrick (edited 04-04-2021).]
Nope. No high idle, but smoke machine found it. The EGR after pulling the vac line and plugging it while searching for other leaks still was blowing smoke. So it's stuck open too since smoke went down the EGR tube. When I hooked the vacuum up again with smoke it was smoking even more. So I would say the diaphragm is gone, and it's stuck open.
The EGR valve is normally closed with no vacuum present. It's engine vacuum that opens the valve. The EGR valve may be stuck open (probably carboned up), but it wouldn't be open due to the diaphragm leaking. You've found two separate issues which will both be solved with an EGR valve replacement.
If you don't believe my take on EGR valve operation, ask The Ogre. He'll set you (or me!) straight.
New EGR comes today, so I pulled the old one...It seems fine... It opens and closes when I pull a vac on it. The gasket however looked boned. I guess we shall see when the new one gets here.
New EGR fixed a lot. It still spit and sputtered once. I put the smoke machine back on it and found another leak....wwwwwaaaaayyyyyyyyy down between the lower plenum and the valve cover. Can't see exactly where, but that's where its coming from. Intake or lower plenum gasket?
It's much much better though I would say 98% there. So looks like the intake is coming out soon.
