Error Code 172 Lean 1994 F53

[semcha]

I am getting the OBD error codes 172 and 334. 172 is KOEO. 334 is KOEO and KOER. The symptoms when driving are a mild hiccup in the engine after driving for about 15 minutes. That is followed by a cascading loss of power to the point that if I have slowed to a stop, I can barely accelerate without lurching. I may be able to get to 25 mph on a flat road, if that. A couple times, I have heard a bang in the engine compartment, maybe a cylinder misfire? It doesn't happen much. If I turn off the engine, I can restart, and drive for about 3 to 5 miles before it starts again. Check engine light comes on sporadically. Doesn't stay on.

I tested the fuel pressure. I get 40 at idle. Up to 45 WOT. The fuel pump was replaced a little over a year ago by the previous owner. Trying to fix this problem, I replaced the MAP sensor, the fuel filter, the fuel pressure regulator, spark plugs, spark plug wires, distributor rotor (cap looked perfect, did rotor just in case), O2 sensor, EGR Control Solenoid (to fix the 334 code, didn't work), vacuum lines to MAP sensor, vacuum line from EGR valve to EGR Control Solenoid, vacuum line from EGR Control Solenoid to the next junction. I previously had replaced the EGR valve and throttle body control, about 7 months ago.

I cleared the codes after each fix. I am going to replace more vacuum lines. I'm at a loss what to fix next or how to diagnose something else. I have looked through the forum for this issue, which is why I replaced the items that I did so far. I appreciate any ideas you may have!

I swear, with each fix, the engine sounds better, but I just can't get this issue fixed. Ugh!

Sean

[subford]

The 172 code is not a KOEO code but a CM code that say the engine is running lean.
The back fire you hear also say the engine is running lean.


The fuel pressure should be about 32psi at idle and about 40psi at WOT.
I do not know if you gauge is off or a bad fuel pressure regulator.
It should never be over 40psi.


It also sounds like your EGR valve is sticking open. Maybe a bad EGR regulator solenoid. This is the 334 code more than likely a CM code also.

[semcha]

The 172 code comes up as Memory on my reader. 334 comes up as Memory and with the KOER scan. The fuel pressure gauge may have been faulty. It was a rental.

I replaced the EGR solenoid two days ago. It didn't fix the issues. Could the EGR valve itself be bad? I replaced the valve 7 months ago.

I replaced the fuel pressure regulator about a week ago. That didn't fix the issue either.

What the best next step?

Thanks!

Sean

[subford]

The EGR valve may be sticking or the wire to the EGR solenoid may be shorting to ground.
The EGR valve may be causing the lean code in CM.


You may also have dirty injectors. If so you could pull the fuel pump relay, the vacuum to the fuel pump regulator and run the engine on injector cleaner keeping the pressure below about 36psi. If you go over 40psi you will send injector cleaner to the fuel tank. That is what I did to mine.

[subford]

You might also try blocking off the EGR tube going to the EGR valve by dropping a coin in the tube where it screws onto the EGR valve and see how it runs.
I do not remember for sure but think the coin was a quarter.

[RideAHD]

Check your catalytic converter, (exhaust) this exact thing happen to us!

[semcha]

How do I connect fuel injector cleaner to the system? The fuel port?

[mpaton]

You say you have checked fuel pressure at WOT and got 45psi, but was this when you were driving, or did you just blip the throttle in neutral?


The lean code you got i most likely to be caused by low fuel pressure under load.


Just because the fuel pump was recently replaced does not mean it is not failing again.



Your loss of power symptoms seem to be intermittent, but the only definitive test for this is to be monitoring fuel pressure while the power loss is happening.


I can't tell if you have managed to already test this way.

[subford]

Originally Posted by RideAHD

Check your catalytic converter, (exhaust) this exact thing happen to us!

He does not have a catalytic converter on a 1994 F53.

Originally Posted by semcha

How do I connect fuel injector cleaner to the system? The fuel port?

Yes it connects to the test port on the fuel rail and it does not use an air hose like the one in the video below.

Here is the set I have:



And it uses:




I also have the one in the video below, the OTC 7448. It uses an air hose and liquid cleaner. But do not let the pressure go over about 37psi for the F53:

https://www.youtube.com/watch?v=Th9nT_3u4mQ

OR


https://www.youtube.com/watch?time_c...&v=9UKEON2wIkA


/

[semcha]

I changed some worn looking vacuum hoses and put a dime on the exhaust connection to the EGR Valve. I checked the vacuum. I am at 17 at 4,400 elevation. Dropped and quickly recovered when I pressed the gas pedal. Drove smoothly and with way more power, so I think that did the trick. Going to shoot for the next city tomorrow. Hoping for the best!

Should I leave the EGR Valve blocked permanently? I checked the wires to the EGR solenoid. I assume I should get 0 ohms with the engine off. I didn't, so I also assume that means I have a short. Is it worth it to rip apart the wires to replace the whole thing? Seems like an ugly job.

I tried to get the fuel injection cleaner. No luck anywhere in Deming, NM, FYI. Just the bottle stuff for the gas tank.

Thank you for your help!

Sean

Originally Posted by subford

You might also try blocking off the EGR tube going to the EGR valve by dropping a coin in the tube where it screws onto the EGR valve and see how it runs.
I do not remember for sure but think the coin was a quarter.

[subford]

I leave the coin in mine as the end of the tube was broke off anyway.
But electrically it is still stock so it does not give me any codes.


Any good repair shop should have the injector cleaner and equipment to install the cleaner.


I would not put Injector cleaner in the gas tank as it may have an adverse effect on the fuel pump and its valves. That may be why a lot of fuel pumps stop working right along with fuel pressure regulators.

[semcha]

I made it the same distance as before, then got the loss of power. 172 and 334 error. On a whim, I unplugged the power connections to the EGR solenoid and EGR valve. I cleared the memory. When I restarted the RV, it took a few more cranks to start. Then I got the check engine light. But it ran. I was able to drive at highway speeds and up steep inclines with good power for about 70 miles. Then I lost power again.

Checked the codes. No more 172. I had 334 on KOEO and MEM, and a others I can't recall from memory about the solenoid and the EGR valve. I plugged in the EGR valve. Cleared the codes. The engine started well. I was able to drive again for another 70 miles or so. CEL came on at some point, but it didn't coincide with any power loss.

At the next code check. Still no 172. Cleared the memory and drove again.

So, 334 seems to be the culprit. I'm thinking I'm now going into Limp Home Mode because of the error code. Does this mean I need to rerun the wire to the solenoid. What diagnostic checks should I do?

Thanks!

Sean

[twinboat]

Could be a blocked muffler.

Vacuum should drop and stay low while stepping on the gas.

If the vacuum climbs, while loosing power, there is a restriction in the exhaust.

[subford]

Was the coin still in when you lost power after 70 miles?