Code 71......Now what?

[Rusty79]

'94 FZJ 80.... 134000 miles...
I have searched through MUD trying to figure this on out.....
I checked the modulator valve and applied vacuum to the EGR valve which seems to functioning fine. I have cleared the code but it came back on about half way through the day. So now what would be the most logical step(s) to take to get this fixed. It does seem like my gas mileage has gotten a little worse than normal. Right now I feel a little stumped....
Any suggestions?

 

[Newps]

Here is my thread and what I did to trouble shoot the problem. My code just went away after a few days and has not returned. Hope this helps.

https://forum.ih8mud.com/showthread.php?t=79300&highlight=code

Tare

 

[Rusty79]

I am checking it out right now thanks...... I did clean alot carbon out of the modulator when I went through it but that didn't fix it.

 

[MoJ]

Rusty -

Please report back on what you find so that I can reap the benefits of your hard work and apply it to my 1994 code 71.

Mine came on about a year ago after wheeling. I reset it and it didn't return until a week ago, after I'd finished wheeling. I haven't started trouble shooting yet.

 

[Rusty79]

Will do..

 

[KliersLC]

Must be preprogrammed.....my 94 w/134k just threw a 71 at me too.....

 

[Rusty79]

That damned little light is staring at me.........It's a conspiracy!

 

[topend yobbo]

I get a funny light that comes on when Im about to run out of juice , how do I cancell it? Goes away after visiting a fuel station.

 

[zipastro]

Try here 70 post and counting, come on in and join the fun!!!!!!
https://forum.ih8mud.com/showthread.php?t=43028
code 71 and PO401 are the same thing, EGR problems
94' would show a code 71 95-97 show po401 because of the newer diagnostic system.

 

[Stumper]

Mine has been on for a month or so, 94 with 135,000 on it......damn the light, damn it to hell. Ill start reading....

 

[Beowulf]

Jimbo and others with the 71 and/or P0401...

Read This thread in the FAQ. It covers the theory and testing of the individual components in the EGR system. Despite the protests of some, the proper repair of the EGR system is quite easy once you understand how it operates.

Post back if you have questions. Many, many guys on this forum have successfully fixed their EGR problems and will be willing to assist.

-B-

 

[CJF]

I am checking it out right now thanks...... I did clean alot carbon out of the modulator when I went through it but that didn't fix it.

Hmm...

On a 91-92, at least, a simple test of the modulator is to see if you can suck air in from the bottom port; if you can, it's shot (busted diaphragm). Cleaning out the carbon won't help; it's still busted.

Curtis

 

[GeoRoss]

dammit, code 71

 

[CJF]

Try here 70 post and counting, come on in and join the fun!!!!!!
https://forum.ih8mud.com/showthread.php?t=43028
code 71 and PO401 are the same thing, EGR problems
94' would show a code 71 95-97 show po401 because of the newer diagnostic system.

Any of you guys frustrated enough yet to try replacing the sensor? (See above thread.) I'll bet that would take care of it for a lot of folks.

Disclaimer: I have no *direct* evidence to back up the above claim. I just honestly think that's what's going on for most people who have carefully checked out the system and are still getting the code.

Good luck to all,

Curtis

 

[zipastro]

Any of you guys frustrated enough yet to try replacing the sensor? (See above thread.) I'll bet that would take care of it for a lot of folks.

Disclaimer: I have no *direct* evidence to back up the above claim. I just honestly think that's what's going on for most people who have carefully checked out the system and are still getting the code.

Good luck to all,

Curtis

I would love to see about 4 or 5 others try this first then I would take a chance myself with the $90 crap shop. Maybe Dan would like to subsidize this experiment?

The most frustrating part about this problem is that just about anything you try makes the light stay off for -awhile- giving you a false sense of success. I Assume that this is because the EGR system is -rarely- activated? I have heard that it only activates when:
*Engine is at full operating temp
*Never at idle
*Never at WOT
*Only when you are traveling in excess of 40 mph and you take your foot off of the gas

anyone else?

 

[Beowulf]

I Assume that this is because the EGR system is -rarely- activated?

This is incorrect.
-B-

 

[GeoRoss]

OK, I made a mistake and washed my 80 this weekend. Not only is it going to rain, but I got my first CEL, ... 71.

I have read many of the posts/FAQ?etc. I have some questions.

The first thing to do is to check all hoses that they are firmly connected and free from carbon build up. What is good stuff to clean said hoses or is it easier just to replace them if filthy?

Check the modulator for carbon build up. If ugly, replace. How ugly should it be before replacing. Can it be cleaned and if so, is there a preferred solvent?

After this, one should put their attention on the temp sensor (clean with what?)


These are the 'easy' things to do, the next step is to check the VSV, EGR, clean the housing.

I guess my main question is what to use to clean these various components and is there a prefered method to clean these components (soaking, scrubbing, ect)?

Thanks and I am glad to join the "EGR-CEL" club

Ross

 

[zipastro]

This is incorrect.
-B-

* Engine temperature more than 170 F.
* Ambient air temperature more than 20 F.
* Engine run time more than three minutes since 170 F.
* Engine speed 2248-2688 (auto. trans.), 1952-2400 (manual trans.).
* Manifold absolute pressure from 5-20 hg.
* Short Term Adaptive Fuel Trim is adjusting pulse width by less than +7 percent and more than -8 percent.
* TP sensor from 0.6 to 1.8 volts.
* Vehicle speed sensor more than 40 mph.
(general rules for generic EGR system)

I guess it depends how you interpret rarely(bad choice of words by me). Would I be wrong to say that out of 60 minutes of average engine run time the EGR system would be active less than 3-5 minutes?

 

[Beowulf]

Zipastro,
While you may think that list represents a series of "rarely occuring" events, it is basically just saying the engine needs to be warmed up and the vehicle speed is over 40 MPH. In fact, these are the same parameters that cause the P0401 to trigger except that the MIL is set after it meets these parms on 2 successive trips.

Would you say your P0401 rarely activates or does it activate just about every 2 trips?

-B-

 

[Beowulf]

The first thing to do is to check all hoses that they are firmly connected and free from carbon build up. What is good stuff to clean said hoses or is it easier just to replace them if filthy?

Ross,

You can use intake cleaner. There is a mesh filter in the EGR modulator that you can blow out with compressed air.

I would do the FSM tests before I got gung ho with the cleaning. If you can blow air through the hoses and passages then they are not clogged. The EGR temp sensor is just a metal probe so clean it with alcohol or anything that will remove the carbon. Again, the FSM tests are your first plan of attack.

Everyone gets freaked out when they have to test the VSV for EGR because it is under the intake and the FSM calls for removing the intake. With some dexterity, you can remove that part without removing the intake. IIRC, there is only 1 bolt and it needs to be accessed with a long extension from underneath going up. Somewhere in the archives I have posted a pic of the VSV with it's bracket in the past. Once you see the pic it will help with figuring out how to remove it and the hoses and the electrical connector.

(Later: Found it....)

-B-