3FE engine "wobbling" or "pulsating" - Any ideas? (1 Viewer)

[Bryan Smith]

Fair enough. For me I’ve replace most of the spark side in the last 10k (cap, rotor, plugs, wires) and just finished replacing most of the air supply side (new intake boot, air filter, Pcv valve, most vacuum lines). When mine does it, if I let off the gas and go to idle I can push back on the pedal and it is better.

Out of curiosity, when you pop open your gas cap do you get a ton of back pressure (hissing)

 

[ashooter]

Fair enough. For me I’ve replace most of the spark side in the last 10k (cap, rotor, plugs, wires) and just finished replacing most of the air supply side (new intake boot, air filter, Pcv valve, most vacuum lines). When mine does it, if I let off the gas and go to idle I can push back on the pedal and it is better.

Out of curiosity, when you pop open your gas cap do you get a ton of back pressure (hissing)

Yeah, I chased a vacuum leak a couple of years ago, replaced ALL the vacuum hoses, and ended up solving a rough/low idle when I replaced the valve cover gasket and all the grommets, and PCV valve. This is different.

When I go to fill up, the gas cap does hiss some... I wouldn't say a "ton of pressure", but maybe I'm just used to it after 15 years.

Edit: This thread might help, if your issue is a vacuum leak -

Good Cruiser mechanics in Texas??? Low idle... At my wits end.

I've been chasing a low/rough idle in my '92 FJ80 for a couple of months. I've done everything I could think of to do, based on many hours of searching here at mud, but this morning the truck barely stays running without my foot on the accelerator, and sounds/feels AWFUL if I just let it idle...

forum.ih8mud.com

 

[ashooter]

Well, apparently (hopefully) I finally got it fixed!

Ran into a guy I know who used to own a mechanic shop, and as soon as I mentioned the "washboard highway" thing, he said "spark plug wire". So, I ordered new wires, and replaced them... Drove about 20 miles, with 3-4 start-ups/shut-downs, and she started the "engine wobble/washboard" thing again.

The next day, I replaced distributor cap and rotor (which I know I SHOULD have replaced at the same time as plugs and wires)... and she seems to be running fine after 100miles+/-, and a dozen or so start-ups/shut-downs.

Keeping my fingers crossed, but so far, so good!

 

[DustyDieselCruise]

Well, apparently (hopefully) I finally got it fixed!

Ran into a guy I know who used to own a mechanic shop, and as soon as I mentioned the "washboard highway" thing, he said "spark plug wire". So, I ordered new wires, and replaced them... Drove about 20 miles, with 3-4 start-ups/shut-downs, and she started the "engine wobble/washboard" thing again.

The next day, I replaced distributor cap and rotor (which I know I SHOULD have replaced at the same time as plugs and wires)... and she seems to be running fine after 100miles+/-, and a dozen or so start-ups/shut-downs.

Keeping my fingers crossed, but so far, so good!

Was this actually the fix for you, or does the story continue? I have the same symptoms, basically seems like a misfire, and have done lots of diagnostics as specified in the service manual with no resolution. Under very slight acceleration I have a relatively smooth running engine. As rpm stabilizes, for example cruise control set at 65 or even 40 I get the horrible miss.

I reset all the valves, new plugs and wires and am going in tonight with new dizzy cap and rotor. Reset and tested tps, cleaned air intake and idle screw to get idle set 650 rpm. Timing was set according to service manual.

At this point I suspected fuel issues, tested fuel pressure and it was slightly high (50psi) but could have been related to the tolerance of the gauge. Now I’m wondering if it could be due to and injector because I have super bad fuel economy even for this engine (8.5 mpg with no lift or bumper or anything other than 33s).

Maybe it is just the cap and rotor I hope.

 

[ashooter]

Was this actually the fix for you, or does the story continue? I have the same symptoms, basically seems like a misfire, and have done lots of diagnostics as specified in the service manual with no resolution. Under very slight acceleration I have a relatively smooth running engine. As rpm stabilizes, for example cruise control set at 65 or even 40 I get the horrible miss.

I reset all the valves, new plugs and wires and am going in tonight with new dizzy cap and rotor. Reset and tested tps, cleaned air intake and idle screw to get idle set 650 rpm. Timing was set according to service manual.

At this point I suspected fuel issues, tested fuel pressure and it was slightly high (50psi) but could have been related to the tolerance of the gauge. Now I’m wondering if it could be due to and injector because I have super bad fuel economy even for this engine (8.5 mpg with no lift or bumper or anything other than 33s).

Maybe it is just the cap and rotor I hope.

Yes. For me, replacing the cap & rotor was the fix.

 

[Marco Lau]

why are Spark plug wires, plugs and rotors not part of your preventive maintenance before you went down that rabbit hole?