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So, I have a beater farm truck ('91 F250 300 i6) and the egr tube is not attached to the exhaust. This is because a previous owner cut out the cats and tag welded the egr tube to the side of exhaust where it's open to regular old air. I've always had code 558 and still do. Recently, I was out getting feed, stopped the truck, and restarted it a few minutes later and noticed a loss of power followed by the power rapidly decreasing until I was just putting along until it overheated and I towed it home.
I checked the codes when I got home and they were as follows:
The active codes are: 114 (O,R) IAT sensor out of range – IAT, 558 (O) EGR vacuum regulator solenoid/circuit failure – EVR or PFE or Solenoids The codes in memory are: 126 (O,R,M) MAP or BARO sensor out of range – “>MAP, 327 (O,R,M) EGR feedback signal is/was low – EVR or PFE
I THINK the EGR has stuck open but I'm not sure. The truck barely runs at idle, the RPMs barely rise when the gas pedal is pushed, and it seems to get hot fast. Also, and I don't know if this is related, the battery light stays on and the dash voltage meter reads low.
A few days later I confirmed that I had fuel pressure, I tinkered around and cleared the memory codes and ran it (barely running as described) up to temp and the only code is 558.
So, if the EGR is stuck open and drawing atmosphere (regular air), what codes should I expect? Is it likely that the truck will run like I've described if that's the case?
EGR open to atmosphere would act like a large vacuum leak, that would produce a high idle but not much else. A MAP sesnor fault could definitely produce these symptoms
Yes, what Hit Man X said (although the IAT code was from the engine being cold) most likely
and,
Check the actual Hertz output of the MAF
If the EGR is open even a little bit at idle, the engine will die
I agree with a EGR block off plate for testing, but hate photochemical smog, so make that EGR work if you can
So let me see if I understand; if the EGR is stuck open even at idle AND is open to atmosphere, vs. exhaust gas, then this will act like a massive vacuum leak. The engine will not likely run or will idle horribly (which it’s doing).
To test or “fix” the problem block off the EGR using the famous beer can delete or some similar method. Then, check the MAP sensor to be sure it’s got proper voltage or is sending signal within the correct range. Is that about right? What should the voltage be to the MAP and what range of voltage should it be sending back to the computer?
The MAP sensor gets a reference voltage (5 volts) from the ECU (processor) and puts out a Hertz signal back to the computer
Pinpoint test steps for code 327 (in the PCED) will go through what you need to do
I have a 93 book (PCED) that lists the 3 digit codes and pinpoint tests, it might be slightly different for your 1991
Use AllData at your library to print out the pinpoint test steps for your 91 and do them
Not all meters read Hertz, it takes a good / fancy one
Good luck
I did the beer can delete (blocked off the EGR) and it made no changes. Ran it at rough idle until it came up to temp, shut it off and checked KOEO and there are no codes in memory. The only code is the 558 (active). Restarted it for a minute and all of the sudden it picked up RPMs, then died, and won't start at all now. I'll let it cool off and try it again but i think the EGR isn't the issue.
Here's another observation that may mean nothing; when it's running at rough idle, there seems to be a good bit of noise at the rear of the engine and especially at the passenger side rear.
Noise is vague. What kind of noise: mechanical like a tap or rattle or whistle from a vacuum leak? A vacuum leak would still make sense since the computer is still setting the EGR code. It cannot apply vacuum to the EGR and see a response from the sensor.
So as stated above the truck just died and wouldn’t restart. Thought I’d check the rotor for corrosion and it was spinning free. Pulled the distributor and the gear was gone. In the second pic you can see it happily perched where I was able to fish it out with a marshmallow skewer. It may be this is the chief cause of the rough idle but what causes a pin to shear like that? IMPORTANT NOTE: I had the distributor apart several months ago and used the original rolled pin when I put it back together which may be the cause of the sheared pin. What’s missing? There it is.
Consider using vac plugs on the vacuum tree off the intake plenum for non essential items. Retain: Fuel pressure vac line, MAP, PCV. Basically get to the bare minimum to operate, then start adding items back like brake booster. Then cruise control. Etc.
Note the PCV hose is difficult to access on these and is often cracked badly. This also could be part of your issue.
Yes behind the TB and below the vacuum tree. I had my upper plenum removed so easy to swap in a new hose. I have not tried with it on so I cannot give advice, sorry.
I have not seen a failed roll pin like that, oil pump drive...yes. Hopefully no damaged caused on your camshaft. Easy to reset to TDC, I like using a welding rod down the No 1 hole and going from there to roll the engine over. The 4.9 you can peek down the oil fill cap and watch the rockers too. Once you are on No 1, back the crank off to 10* BTDC and stab the distributor again. Obviously recheck the timing when the engine is hot with the SPOUT connector pulled.
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