FJ62 runs rough climbing hills, timing issue? (1 Viewer)

[PF]

ok, need some help on this one. The truck runs great most of the time. But when I'm driving up hills at freeway speeds it starts running rough. This starts about 10 seconds after I start climbing a descent grade. First the exhaust tone changes from deep and throaty to light and airy. If I stay on gas the truck starts to lose power and run rough. If I let off the gas the problem quickly dissipates. Also this only happens above 2500 RPM. If I change gears (I have a 5 speed manual) and lug the truck up hill at lower RPM it does not do this.

I thought the fuel pump or rail regulator might be going bad so I tapped into the fuel rail at the cold start injector line and rigged up a mechanic fuel pressure gage in the cab. Fuel pressure is solid. Definitely not that.

Because of the way the problem fades in when I'm on the gas and fades out when I let off, I'm thinking it's the timing. I had it advanced before the problem started. Now I reset to factory 7deg, but the problem still exists. I do not fully understand how the 3FE timing advance works. Could something have broken in the distributor? Distributor vacuum filter plugged? What do the wires going into the distributor do? Does the ECU control the timing on the 3FE or is it purely mechanical?

Thanks for your help.

 

[PF]

OK, the only thing I've found out is that timing on the 3FE is ECU controlled and my ECU isn't throwing any error codes. Based on the zero response rate I'm guessing this is not a common problem. Also, I'm still assuming it's timing related but haven't found anything directly wrong with the timing. Anyone? Bueller? Bueller?

 

[SteveH]

Weak spark due to failing ignitor? Have you done a full tuneup - cap, rotor, wires, plugs? Rock Auto (Denso) parts will be cheaper than the dealer - especially the plug wires. Be sure you only use NGK or Denso spark plugs - not evil Bosch or yucky Champions.

 

[FJ40Jim]

Is it misfiring, actually dropping a cylinder(s) under load? If yes, it is not timing. The timing being off by 10 degrees will push down the power curve, but it won't cause a misfire. Actually misfiring is either a weak spark (failing wires, plugs, coil, etc) or AF mixture is too far off to light.

 

[NYNick]

Here....https://forum.ih8mud.com/threads/fj62-heavy-hesitation-tranny-bucking-a440f.741216/#post-8865165

I never did resolve this problem. I'm guessng a new cap and rotor would be a good idea based on the responses to my thread.

 

[RodrigzCrzr]

Check for any cracks in your vacuum hoses as well!
One slight hole and can throw it off.

 

[RodrigzCrzr]

Also check EGR !

 

[Ogremoody]

Seven degrees with computer disabled? When I bought my 62 it had power issues due to it being timed without disabling the computer. I found a 3fe factory manual someone had a drop box link to. It should be timed at seven degrees with the computer disabled. It ends up being like twelve degrees before tdc when you enable the computer again. I can find the info and confirm if you want. Don't go off just my memory! It made a huge difference in how much power the 3fe made. Then I followed the factory tps adjustment procedure and have a smooth add ice idle to go with all the power.

 

[LAMBCRUSHER]

good point Ogre...jumper t1 and te1 in the ecu diagnostic box and set timing to 7*; remove jumper to set back into closed loop

 

[PF]

OK, thanks for all the good advice. Here is where it's at...First, I checked the rotor, cap and plugs. I clean everything a little, but they are all relatively new (about 10k miles).

Then I checked the timing. It was way OFF!! This is the result my last trip to the smog shop and a misunderstanding between me and my smog guy. Long story, but my truck has been running at 0*. So I fixed THAT! Timing is now at 7*. Yes, I used the jumper, thank you.

So, did that fix the problem? No. But it did change it. Here is the thing, the problem only kicks in when I'm hauling ass up hill at 60mph. And it doesn't start right away. Before, when the timing was off, it took about 10 seconds to start making noise and loosing power. Now, with the timing set right, I can be going up that hill for a couple minutes and pushing the truck pretty hard, but it does eventually start to sound funny followed by the same power loss. It doesn't sound like it's dropped a cylinder.

Tonight I checked the ERG valve as well as the other thing next to it (VSV?) and the solenoid. All completely functional. I also checked the TPS. Also working.

Here is my next step. I had a chance to speak with Martin at Martin Davidson automotive. He build my engine. I noted that during break-in the engine consumed a far share of oil. Also, I've got aftermarket Cats that are over ten years old. He thinks it's possible that those cats are partially plugged. Maybe from the poor timing, maybe from the initial oil consumption, maybe from age. He said if my exhaust is backing up, intake vacuum will drop off. I'm going to rig p a vacuum gage in the cab and see if the problem corresponds to vacuum decrease. IF it does, I'll drop the exhaust and see if it will do it, unplugged.

Still looking for backup ideas. Does anyone know what sensors or engine conditions the 3FE computer uses to adjust timing?

 

[LAMBCRUSHER]

the tps needs to be calibrated- even a new one; sometimes an old one will get out of adjustment. the sensor in the AFM on the intake can could also be experiencing some fooyness- those 2 things and the O2 sensors give ques to the ecu for fuel trim and timing. Did we check the air cleaner filter and the air cleaner to intake duct for cracks?

 

[PF]

Thanks for the replies. I checked the TPS, only made a slight tweek. Cleaned the Air filter. Also adjusted the timing. From what I can tell it was a timing issue. Changing the timing had the biggest effect on how it runs even though the FSM seems to say that the ECU determines when to throw the spark. It runs fine now. 65mph up hill in 4th gear no problem. Rock n Roll!!