Are all 5.0L EGR valves the same? Code 34.

Posted by: Bluwaggo

Are all 5.0L EGR valves the same? Code 34. - 02/24/21 09:18 AM

Background: The Red CEL of Doom (TM) has been making itself known and after changing my shorts, I picked up an OBD tool and found out it's just a code 34 and a code 10.

Relevant: I have my smog pump removed and I've recently redone most of my vacuum lines with rubber--the vinyl simply kept breaking.

I'm going to take another pass through the vacuum setup to make sure I've got that configured properly (the smog solenoids are still in place and plugged but I guess I could just remove them) but assuming my problem is actually a bad EGR, are all 5.0L solenoids the same? It looks like there's two different sensors (beige and black), but what about the valve itself? It would be really nice to just be able to grab whatever NOS exists on ebay.
Posted by: Bellwestern80

Re: Are all 5.0L EGR valves the same? Code 34. - 02/24/21 09:08 PM

So there's two "engine" lights on some '89s.

The red 'ENGINE' light comes on for two reasons: High coolant temperature or low oil pressure.

The amber 'CHECK ENGINE' light comes on like any modern check engine light.


Regarding the EGR, you can certainly try cleaning it first. It can get carbon buildup on it, or the sensor attached to it may not be in good shape. As long as the vacuum line is still going to the correct solenoid on the fender, you should be okay. If you want to replace it, any car SEFI one will do, same for the position sensor. The color doesn't seem to have any affect to it working.

Leave the old smog solenoids plugged in, otherwise the car will code out for those being absent. Only way to really make those go away is to determine their resistance values and find a suitable resistor you could put in line to the circuit to fool the computer. I don't have my smog system either, but those solenoids are still mounted, albeit with no vacuum going to them and no lines running off of them.


Moving away from that and back to the red 'ENGINE' light, does it flicker or stay on steady at any times?
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/24/21 09:31 PM

I thought it was crazy for the EGR to trip the red one, so....

Yeah, it stayed on for about 5 minutes while I finished driving to work, then about another 5 minutes driving to an appointment after work. No flicker.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/24/21 09:33 PM

Also, the water pump is new and the thermostat is new, so I guess it could be oil pressure. It's there a good place to tap for an oil pressure sender?
Posted by: Bellwestern80

Re: Are all 5.0L EGR valves the same? Code 34. - 02/24/21 09:51 PM

Usually oil pressure gets the flickering issue at idle, not driving. Not impossible if it's not maintaining pressure at cruise though. IIRC, the temperature switch will throw it north of 280* and the oil pressure goes at less than 4 PSI.

That said, Ford not giving us any gauges besides speed and fuel was dumb. There's an extra port you can thread into for the oil pressure near the oil filter. You may need to get a small extension fitting to give yourself enough clearance. Best thing about that extra port is that allows you to leave the warning light switch in place for extra attention. FWIW, I'm thinking if you have low oil pressure at cruise, the engine would be making some pretty interesting noises.

I'd also recommend adding a temperature gauge so you know what its doing so you don't accidentally cook anything. You can replace the switch on the driver's corner of the intake with a sender. Also, while it's nice to think all new parts are good, I did have a sticky thermostat on my '97 that would stay shut way too long. The needle would get almost to the top of the normal range before it rapidly fell off as the thermostat finally opened. Swapped it for another and it stopped doing that.

Hopefully you're not actually experiencing any serious issues and its a flaky switch at one of those points, but give yourself some assurance with real readouts. The warning light is too little, too late.

I'm currently running just a temperature gauge to the left of the steering column, but I have plans for a tri-gauge setup that mounts under the ashtray that'll incorporate temperature, oil pressure, and volts.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/24/21 10:38 PM

I felt the hoses after my last drive and while the upper rad hose felt normal, the hose that runs from the temp control to the front of the engine was extremely hot.

And yeah, 4psi is basically catastrophic. Still, the light went out after I swung a U-turn and I would think that points to oil. Oil level is fine, of course.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/25/21 10:23 AM

I ordered a Bosch water temp gauge which should be here Saturday. I need to find a less expensive electrical oil PSI gauge and then I'll install that. The Bosch mechanical gauge is only $20 but I'm not a big fan of running an oil line inside the car. I did it in my Mercedes and never felt quite safe.
Posted by: Bellwestern80

Re: Are all 5.0L EGR valves the same? Code 34. - 02/25/21 10:50 AM

I used one of these electric oil pressure gauges in the ‘97: eBay Link
Works good.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/25/21 12:02 PM

Well, that works! Thanks for the tip and it's on its way.

For the coolant sensor, I bought a 3/4" in-the-hose-sensor-block-adapter-thingy. I'll pull out the auto temp control module (heater core is bypassed anyway) and put it right there. That hose was screaming hot, so should be a good place for it.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 02/25/21 12:09 PM

And I'm kicking myself for not testing the thermostat before I installed it.

When I replaced the (Stant 195deg) thermostat, I also replaced:
Gates water pump
GMB thermal clutch fan (clockwise rotation)
Carquest radiator
Carquest radiator cap
Carquest rad hoses (top & bottom)
Gates bypass hose
Dorman thermostat housing
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 03/07/21 11:12 PM

Tried burping the cooling system while up on ramps... Didn't seem to need it and the RCELOD came on once the car seemed to warm up.

I got under the car to see my options...I assume the bolt roughly center of the photo, just left of the oil PSI sensor is the extra port you mean? Under the chrome hard line.

https://photos.app.goo.gl/uPWLXFUQ139FnhTq9

And then on the front drivers side of the intake manifold, I found what's presumably the temp sensor. I guess stick a T on that? Is that also 1/4" npt?
Posted by: Bellwestern80

Re: Are all 5.0L EGR valves the same? Code 34. - 03/08/21 06:40 AM

Regarding the oil pressure port, maybe I’m mistaken about the existence of the second port. You may just have to tee off from where the factory switch is if you want the switch and sender.

And the switch you found on the intake sounds correct for the temperature one. Regarding the thread size, it is NPT, but I don’t recall the pitch.
Posted by: Old_Guy_Stu

Re: Are all 5.0L EGR valves the same? Code 34. - 03/08/21 07:54 AM

Even when Ford included an oil pressure gauge (Mustang, T-bird, etc), it's nothing more than a warning light. Anything over 4-6 psi pops the needle into the middle of "normal" and it stays there.

Don't put a tee in the coolant passage on the manifold. The sensor needs coolant flowing past it. Putting it in a tee will isolate the sensor. Better to use a tee and some nipples on the heater hose.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 03/08/21 12:00 PM

Upper hose or lower hose or doesn't it matter?
My opinion is that if the light trips at 280, then I'm going to see north of 200 no matter where the sender is installed and that's going to tell me I have a cooling problem (with a 195 deg thermostat).

I also decided to grab some replacement OE sensors in case it's just a matter of them going bad. And I'll cut up my oil filter in case it's blocking flow. Gotta try my best to consider Occam's Razor!
Posted by: Old_Guy_Stu

Re: Are all 5.0L EGR valves the same? Code 34. - 03/08/21 12:25 PM

Outlet hose to the heater (the one with the goofy vacuum valve in it) will give you the highest (most accurate) reading.

I'm betting on a bad sensor. If you had either 280F or 4 psi for very long, your engine would be toast.
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 03/08/21 01:33 PM

They was my first thought as well--remove the auto temp control and replace it with a tube splitter/adapter. Unfortunately, the one I ordered is too shallow to allow the sender to thread in. Maybe I just need to make something out of brass fittings...
Posted by: Bluwaggo

Re: Are all 5.0L EGR valves the same? Code 34. - 04/07/21 02:39 PM

A backyard landscaping project has stolen a lot of my spare time since this problem developed, but I can finally make an update.

Virtually anything that could have gone wrong went wrong.

- The temp sensor is the wrong one (two wire vs my one wire).
- The very expensive custom brass rig I built to go in place of the auto temp sensor keeps the sensor just enough out of the flow that I don't get an accurate reading and I need to splice the upper rad hose. Otherwise, it looks like the coolant is 100* at operating temp rendering the gauge effectively worthless.
- The copper splitter I bought technically does install just fine but I can't attach anything to it. It needs extensions or 45s or both or something. So I just installed the new oil PSI sensor, which thankfully is the correct one, back into the port. I would have installed the gauge instead, but the sender won't fit in that space without help.

All that mess said, I idled the car for at least 15 minutes, it definitely came up to temp, and there was no RCELOD.