Hi, check engine light came on with my 1991 4x4 F150, XLT Lariat. I felt like there was a small stutter in the car around the same time the light came on, but maybe it's unrelated. Truck is also running fine. Anyway, picked up an OBD1 scanner, made sure the car was warmed up, then ran the key on engine off test. Only code I got was 84. After looking up the code, it says EGR Vent fault. Anyone ever got this before, or any suggestions on where to start? Seems like it could be a few things from what I've read, but I have zero experience with reading/troubleshooting obd codes. My rear anti lock brake dashboard light is also on, but its been like that for about 2 months, and occasionally turns off. Not sure if that's relevant or not. Thanks for any help!

 

You would get better results if you posted this in the forum section for your era of truck...

 

https://www.f150forum.com/f10/code-8...-fault-164983/

 

Got it, i see the sub-forums now. Thanks!

 

Thanks! This could be pretty helpful.

 

You should put ALL the truck's details & history into your signature as this page explains:

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You should return it for refund ASAP. They are NOT reliable on these early EEC-IV systems, and are known to display spurious codes....and their code definitions are usually RONG. There is no "EGR vent", so there can't possibly be a fault with that. Read this page (it's long) a few times, and then read codes using a jumper wire.

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The first step in diagnosing any code on any vehicle is to find out if the indicated condition actually exists.Read this page & the NEXT several:

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Apologies for the delay! I did the jumper wire method and still got a code 84. That's good to know the obd1 scanners are not reliable though. The scanners code definition is total garbage. Looked up 84 online and it says "EGR vacuum control solenoid circuit failure" . So, making progress. Looks like there's no vacuum coming out of the EGR vacuum control solenoid, so i think the solenoid is faulty. Either that, or the vacuum tube line is completely busted. But I guess what I'll do is use my vacuum hand pump tomorrow on the tube that enters the EGR valve. If the engine stutters at idle, that should mean the valve is working correctly and the vacuum tube is still holding a vacuum ok. That seem right? Any other tests I should run? This tutorial was extremely helpful: https://m.youtube.com/watch?v=xWpqhdQH01Q From what I can tell, this person was having the same issue I was. Also wanted to ask what I should do if i replace the EGR vacuum control solenoid, should i just disconnect the battery for 10-15 min to clear the codes from the computers memory? Is that necessary? Thanks for the help! I updated my signature too!

 

Online is usually just as bad as the scanner - you should always use the link I posted above.In this rare case, you found the correct definition. But it doesn't look like you actually READ that definition.Re-read the code definition - it has nothing to do with vacuum; it's a CIRCUIT fault. That's electricity - not vacuum.No, you're jumping out of the scope of the code, and guessing.Nothing because you still won't have tested anything related to the code definition, or learned how that system works.

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You should ONLY run other tests - not anything you posted. Get a decent digital multimeter (DMM; $20~80 is plenty) with good batteries. It does NOT need to have the inductive clamp that this one has:

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Other people are irrelevant to YOUR TRUCK'S problems. Focus on YOUR TRUCK.No, you should read the link I posted about codes.It's not showing anything. Did you click the signature link in my previous post? Did you save your changes? Did you check the box to automatically add your signature?

 

My signature should be set, hopefully it works this time.

I do have a multimeter and took some measurements from the power wires that input into the EGR vacuum control solenoid. Looks like I should be reading 12 volts with koeo, but I'm only getting 9 volts. I assume this is a problem, from what I've read this will not be enough to activate the solenoid and I need to find out why I'm missing 3 volts. My battery is good, reading a solid 12 volts.

I appreciate the links, i have been looking them over and its getting easier to understand. Im going to keep reviewing them.

 

Nope, still no signature. Can you see mine? Try either on a computer with a fullsize monitor, or in a real browser (like Chrome - not a posting app) on your phone.

To find out if 9V is enough, simply ground the EVR wire (NOT the red one) with the key in RUN. If you hear the EVR click and it suddenly passes vacuum, it's enough. But voltage is not measured AT a point; it's measured BETWEEN two points, so it matters where you put the black probe. The EVR wire is not the right place for it - it should be on the engine/body/ground, or the B- post.

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