94 2.3l ranger rough idle

[bmostowy]

I'm new here so take it easy on me if I'm doing something wrong.

With that out of the way, I'm looking to get some advise: I've got a 94 with the 2.3 four banger which has run like a top until recently. It started idling rough and stalling out at idle a few weeks ago, it still cruises alright, and I haven't noticed a significant dive in gas mileage. I replaced the plugs and wires when I bought the truck about a year ago, and I dump some sea foam in it every now and then to keep it clean. I have no service lights on, but when I run the KOER diagnostic I get a code 172 "Oxygen sensor not switching – system is or was lean – Single, Right or Rear HO2S – Fuel control." KOEO returns 111, all systems normal. I've since replaced the O2 sensor, MAF, and IAC valve to no effect. Going off the "Lean Condition" code, I did what I would do to a bike or quad: start spraying Carb & choke cleaner around looking for an air leak. I found one possible leak: on the back of the EGR valve, there are holes in the housing, and when I spray them, the engine picks up.

Is this normal, or should I replace it? I'm just looking for advice before I throw any more parts at it.

Thanks Guys

 

[XLTsplash]

You can test the EGR valve with a hand held vacuum pump. The EGR valve should hold vacuum. If you apply vacuum to it with the engine at idle it should run very rough or die, when you release the vacuum the valve should close.

 

[bmostowy]

Thank you, I'll give that a try tomorrow.

 

[tomw]

You likely have a perforated EGR vacuum diaphragm. If there is a hole, air will get pulled into the area behind the diagphragm, and fed into the intake. You can disconnect the tube and plug it with a golf tee. If you idle smooths out, I think you've found your trouble source.
OTOH, there is not supposed to be any vacuum to the EGR at idle...

tom

 

[bmostowy]

Thanks for your input guys. I installed a new EGR valve today to no effect. The engine still picks up when C&C cleaner is sprayed on the back of the diaphragm housing, so to ensure this wasn't the cause, I put a thin piece of cardboard in between the manifold and the valve. The engine still idled rough, but when I sprayed around the valve, it didn't pick up. I started looking for other air/vacuum leaks, and I believe there is one the part in the picture, not at the fittings, but around the black plastic cap on top of the solenoid, so I think that's what I'll try next, unless you all have any different recommendations.

Thanks

 

[tomw]

The trouble reported for KOER may be a temperature related thing. If the O2s are not warmed up all the way, they won't switch or report ANYthing. And that is 'lean' by definition of the O2 operation.
I do not have one of those solenoids on my old truck. What do the green and red tubes connect to? If the solenoid is a 'vent to atmosphere' in one of its modes, i.e., dump the vacuum signal..., then I'd think it would not affect engine running, or at least should not.
The EGR on mine has two valves. One to apply vacuum, and one to dump or hold vacuum. The 'dumper' operates on signal from the computer, which has been 'told' by the EGR exactly how far open the valve is. The computer picks the 'point' it likes, opens the vacuum 'apply' solenoid, lets in vacuum, closes the apply, then operates the dump to get the valve positioned as it wants. The vacuum is NOT bled to atmosphere all the time, only when it is not needed any more.
I guess I'd ask at a parts store to see one of those solenoids, bring a long a piece of tubing, and suck on the port connected to vacuum on your truck. If it holds vacuum, you need a new solenoid as yours is apparently letting air flow into the port via a rupture or failed valve. I think.
tom

 

[bmostowy]

For those who responded, thank you, and I'm happy to report I resolved the issue. For anyone who is wondering, the problem was very simple, a stuck one-way valve on a breather line (see picture)

 

[Jmiddleton95]

How did you fix the problem? I think I'm having the same issues