Step 1 baselining (91 FJ80) - Off with a....thud. (1 Viewer)

[BlutoF15]

Well, technically step two I suppose, but since step one was changing the oil and checking the transmission fluid (surprisingly good) I wouldn’t count that as anything beyond normal maintenance.

I got my Wits End tune up kit and was stoked. Finished up last night with the new plugs, wires distributor cap, rotor, and vacuum lines. Distributor and rotor were average shape, wires were actually pretty good, plugs were awful.

Went quite smoothly, especially compared to what I anticipated.

Started her up today to take a ride, no need. Runs rougher than before, a bit of smoke, and popped a CEL where there was none with a 31 code.

Vacuum lines triple checked, good. Nothing broken, no missing parts, nothing disconnected. That great feeling of satisfaction after reassembly and beautiful new OEM parts turned right into ugggghhh here we go...

Suggestions?

 

[proteolytic]

Well, technically step two I suppose, but since step one was changing the oil and checking the transmission fluid (surprisingly good) I wouldn’t count that as anything beyond normal maintenance.

I got my Wits End tune up kit and was stoked. Finished up last night with the new plugs, wires distributor cap, rotor, and vacuum lines. Distributor and rotor were average shape, wires were actually pretty good, plugs were awful.

Went quite smoothly, especially compared to what I anticipated.

Started her up today to take a ride, no need. Runs rougher than before, a bit of smoke, and popped a CEL where there was none with a 31 code.

Vacuum lines triple checked, good. Nothing broken, no missing parts, nothing disconnected. That great feeling of satisfaction after reassembly and beautiful new OEM parts turned right into ugggghhh here we go...

Suggestions?

Did you reset the ECU? Reset ECU (remove EFI fuse or disconnect batter for 15 or so minutes) after doing anything under the hood no matter how simple otherwise computer will run it using stored parameters from your old parts.

 

[BlutoF15]

Unhooking battery now, I’ll give that some time, thanks for the explanation/background! I would have definitely assumed that it wasn’t necessary for “just” the stuff that I did.

Still nosing around through old threads/info. I didn’t disconnect the plug to the airflow sensor while I had everything apart for fear of causing an issue but that’s on my official worry list. I left out above that I also threw in a new OEM air filter - which also makes sense for requiring a reset. Lots of new variables in the chain, I suppose.

Thanks again, we’ll see how the reset goes.

 

[BlutoF15]

Oof.

CEL still on though I’m suspecting that requires a manual reset.

Left battery disconnected for about 20-30 minutes, started quicker but runs a little worse. Trying the EFI fuse now as well for another attempt.

Worried about the plug wires as well, and their connections. It seems like the #1, 5, and 6 are at the max end of their travel - any chance that’s causing the rough idle? (Still doesn’t cause the 31 code though I suppose.)

 

[proteolytic]

Oof.

CEL still on though I’m suspecting that requires a manual reset.

Left battery disconnected for about 20-30 minutes, started quicker but runs a little worse. Trying the EFI fuse now as well for another attempt.

Worried about the plug wires as well, and their connections. It seems like the #1, 5, and 6 are at the max end of their travel - any chance that’s causing the rough idle? (Still doesn’t cause the 31 code though I suppose.)

Resetting ECU will clear stored CEL codes (EFI fuse or battery is sufficient but both are not needed). EFI fuse is the easiest IMO.
When you say runs a little worse what do you mean? Bad idle? Bad acceleration? Did the CEL come on right after starting it up or did it take a few minutes of driving? When you changed the air filter if you unplug the AFM (if not perhaps you put too much strain on the wires when lifting it up)?
Before you did anything did it run fine with no problems?
You can also post pics of the things you changed for folks to see if something doesn't look correct.

 

[jonheld]

Well, technically step two I suppose, but since step one was changing the oil and checking the transmission fluid (surprisingly good) I wouldn’t count that as anything beyond normal maintenance.

I got my Wits End tune up kit and was stoked. Finished up last night with the new plugs, wires distributor cap, rotor, and vacuum lines. Distributor and rotor were average shape, wires were actually pretty good, plugs were awful.

Went quite smoothly, especially compared to what I anticipated.

Started her up today to take a ride, no need. Runs rougher than before, a bit of smoke, and popped a CEL where there was none with a 31 code.

Vacuum lines triple checked, good. Nothing broken, no missing parts, nothing disconnected. That great feeling of satisfaction after reassembly and beautiful new OEM parts turned right into ugggghhh here we go...

Suggestions?

31 is AFM.
Likely you tore the intake plenum when replacing the air filter.
Unmetered air anywhere in system will cause a rough idle.
As previously mentioned, it is good practice to remove the 15 amp EFI fuse whenever working under the hood. It will clear out old stored codes and allow the ECU to relearn the sensors. Think of it like rebooting a computer.

 

[BlutoF15]

Yep, makes sense, just wanted to disco the battery in case I didn’t time the fuse removal correctly or something. Neither worked.

Apologies for the “now it’s worse” vague comment.

Truck ran “fine” until yesterday. I say fine as in no CEL, idled mostly smooth (to be 29 years old) but certainly felt in need of a tune up. Felt bogged down under acceleration and with a very mild shudder.

Replaced air filter, plugs, wires, distributor cap, rotor, and all of the vacuum lines on the drivers side “half” of the motor, finishing up the rest now.

CEL stayed on from immediately after start, slightly rough idle, slightly high (about 800rpm) and slight smoke from exhaust.

Reset EFI fuse/battery disconnect, and it seems to run a bit rougher now, but that could be just perception. Definitely rougher than prior to parts change. Attempted to reset CEL light, no luck. CEL is on at switch to on and stays illuminated.

 

[BlutoF15]

Only thing not installed in the picture is the distributor boot, just haven’t put it back on yet.

 

[BlutoF15]

31 is AFM.
Likely you tore the intake plenum when replacing the air filter.
Unmetered air anywhere in system will cause a rough idle.
As previously mentioned, it is good practice to remove the 15 amp EFI fuse whenever working under the hood. It will clear out old stored codes and allow the ECU to relearn the sensors. Think of it like rebooting a computer.

Gotcha, makes sense to me. The fuse pull is about as easy as it gets.

On the other hand, torn intake plenum sounds firmly in the “uh oh, that’s not good” category. The harness going into the top here appears VERY brittle. I did wiggle it and it sounds like broken glass in there.

 

[jonheld]

Gotcha, makes sense to me. The fuse pull is about as easy as it gets.

On the other hand, torn intake plenum sounds firmly in the “uh oh, that’s not good” category. The harness going into the top here appears VERY brittle. I did wiggle it and it sounds like broken glass in there.

Typically the plenum will tear on the underside of the bellows as you lift the cover of the air filter housing. The top half of the 3FE wants to be as air tight as possible. Unmetered air is the most common cause of rough idle. The gasket on the oil fill cap, the gasket on the oil dipstick, the 4 valve cover grommets, the PCV valve gasket, side cover gasket, valve cover gasket are all places that need to be air tight.

80 Series 3FE Intake Air Hose Kit

80 Series 3FE Intake Air Hose Kit (AIH-3KIT)

absolute-wits-end.com

 

[jonheld]

General Tech - 3FE Tune Up Info

3FE Tune Up Info

forum.ih8mud.com

 

[BlutoF15]

Typically the plenum will tear on the underside of the bellows as you lift the cover of the air filter housing. The top half of the 3FE wants to be as air tight as possible. Unmetered air is the most common cause of rough idle. The gasket on the oil fill cap, the gasket on the oil dipstick, the 4 valve cover grommets, the PCV valve gasket, side cover gasket, valve cover gasket are all places that need to be air tight.

View attachment 2630074

80 Series 3FE Intake Air Hose Kit

80 Series 3FE Intake Air Hose Kit (AIH-3KIT)

absolute-wits-end.com

On it. I see what you mean now re/plenum tear. I’ll pop it back off and verify that isn’t an issue. I did see that air intake hose kit when I ordered the tune up kit but it was out of stock. May as well try again for a true baseline. The valve cover gasket and all associated grommets will be another bad weather full weekend project. I *think* (famous last words) that I can rule those out for this suddenly appearing issue, since I didn’t touch them yet.

But...I started wiggling stuff so anything is possible!

 

[BlutoF15]

Now I’ve done it.

Funny how easy it is to find specific info AFTER you royally foul it up. I found the issue. Guess who is the issue?

I murdered my AFM via the two deadly screws. I now have loads of threads researched telling me not to do that. I thought I was avoiding it by not trying to remove the metal retainer, and just use the “obviously easier” method of popping two Phillips screws out. You all know how this ends.

Now to find a replacement. MOAR ADVENTURE!

 

[TomOsborne]

lol fatally flat Florida. Those screws are inviting I have a spare if you need it. Im in Wakulla (Tallahassee). I'd like to hang onto it ideally, but if you cant find one I can help. I dont remember if you can get Chinese junk from Rock Auto for an AFM.

 

[zayets]

I've read on here you can do a swap the stock AFM for a camry MAF but I'm not 100% sure if its plug and play or if there is some type of conversion involved. I'd be curious if anyone knows more about this mod.

 

[BlutoF15]

Lol - I like me some fishing so it’s not all bad, but we will certainly never understand the struggle of our rock crawler and high altitude overlander brethren.

Thats very generous of you, much appreciated! I’ll take a reservation on it just in case but see if I can source one otherwise before you burn a good spare.

I’m digging up info to see if this is even worth the 10 minutes it would take to install it.

Herko Chinese junk

Cheers!

 

[TomOsborne]

Lol - I like me some fishing so it’s not all bad, but we will certainly never understand the struggle of our rock crawler and high altitude overlander brethren.

Thats very generous of you, much appreciated! I’ll take a reservation on it just in case but see if I can source one otherwise before you burn a good spare.

I’m digging up info to see if this is even worth the 10 minutes it would take to install it.

Herko Chinese junk

 

[TomOsborne]

My spare could be junk itself. It was on when I bought it, suspected it was bad, found a used one and didnt change a thing so now i have a couple. Got a few parts like that come to think of it...

 

[highsierra4x4]

Lol - I like me some fishing so it’s not all bad, but we will certainly never understand the struggle of our rock crawler and high altitude overlander brethren.

Thats very generous of you, much appreciated! I’ll take a reservation on it just in case but see if I can source one otherwise before you burn a good spare.

I’m digging up info to see if this is even worth the 10 minutes it would take to install it.

Herko Chinese junk

Cheers!

the 93 camry v6 will work I had the same issue on my 92 it was a cel light rough idle and white smoke from running so rich went to O'reillys and picked up a camry one fixed it right up

 

[BlutoF15]

My spare could be junk itself. It was on when I bought it, suspected it was bad, found a used one and didnt change a thing so now i have a couple. Got a few parts like that come to think of it...

Ahhhh, gotcha. Well, if I find out that the eBay guy that remans 93-94’s will/can do the 3FE’s all pass that along. That at least gives a rebuild option.

Still good to have a pile of spares even if they’re a “maybe” - for when you do something like I did and turn something into a “aw hell no, that’s broke.”