Exhaust "Pulsation"

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nmcbride89

nmcbride89

Joined
May 24, 2016
Threads
18
Messages
71
Location
Baton Rouge, LA
Does anyone know what's going on here? It was doing this for a few days, along with a high idle (1000 rpm in park, 750 when stopped in drive), but then it quit and idled perfectly for like two weeks. Now it's back, along with the high idle.

I know that at least one O2 sensor is bad (checked for codes, and the only code was for faulty O2 sensor), and my truck seems to be running rich lately (based on the smell of the exhaust). I have the replacement sensors, but I need to get my exhaust reworked - have the parts I need, just need to get it to the shop (and get my wallet ready...).

One of the POs really did a number on the exhaust when they removed the cats and installed a Flowmaster muffler. Basically, they tied the downpipes together and did a terrible job. There is at least one hole in one of the welds, which could either be leaking exhaust out or air in...

I replaced the spark plugs, wires, rotor, dist cap, fuel filter, and fuel pressure regulator. The PO replaced the fuel pump. Since the problem is intermittent, could it be related to the O2 sensors?

 
To ok this was talked about a while back but is basically standard due to the pattern at which the cylinders go. Mine sounds and looks the same way. Look at the valve adjustment pattern and you will see what I mean.
 
I guess I'll need to go back and search again. Sorry if this has been brought up before...

I can feel the pulsation through the truck, and it seems to make the RPMs blip down when it happens, especially when it's really acting up. What's weird to me is that you can't really notice anything under the hood in terms of sound or anything while it's going on.

My valves are making some noise, so that's on the list to address in the near future.
 
Bet that your "blip" will go away with a proper valve adjustment and tuning. When was the last time you did the normals; cap, rotor, plugs, wires, timing, other adjustments?
If I remember correctly there was not a dedicated thread to it, just something that came up in discussion and it was due to the way the cam and lobes were (could be complete mis-remembering though). @FJ40Jim @Spike Strip @orangefj45 @NCFJ @beno @cruiseroutfit
 
I'd start with a compression test.

Then adjust the valves, do a tune-up ( if it hasn't been done already ) and then check compression again.

That's always a good start.

Since you've already completed the tune-up, I'd say replace the O2 sensor since it's a known issue and can/will affect how the engine is running.
 
gregnash said:
Bet that your "blip" will go away with a proper valve adjustment and tuning. When was the last time you did the normals; cap, rotor, plugs, wires, timing, other adjustments?
If I remember correctly there was not a dedicated thread to it, just something that came up in discussion and it was due to the way the cam and lobes were (could be complete mis-remembering though). @FJ40Jim @Spike Strip @orangefj45 @NCFJ @beno @cruiseroutfit
Click to expand...

I just replaced the plugs, wires, rotor and distributor cap a month ago. Also replaced the fuel filter and fuel pressure regulator.

I have not looked at the timing or the TPS, yet. By the amount of noise my valves are making, that is on the short list of things to look at once I get my O2 sensors replaced with the exhaust repairs.
 
May want to check your Fuel Pulsation Dampener as well, my FJ62 has the same issue but it seems to diminish just slightly when that dampener screw is tightened down and mine seems to come loose occasionally.
 
CaptHamster said:
May want to check your Fuel Pulsation Dampener as well, my FJ62 has the same issue but it seems to diminish just slightly when that dampener screw is tightened down and mine seems to come loose occasionally.
Click to expand...

I have a new one, just haven't installed it yet because I need a crowsfoot wrench.

The screw was out of it a while back, and I tightened it back down. I just checked it again when the blip started back, but the screw was in place and seemed tight...

I definitely need to do the damper and valve adjustment, but I'm still wondering if it's O2 sensor related. Why else would it have stopped and idled perfectly for a while? The weather has been the same (hot, rainy, and humid) for the past two months, so that shouldn't be a factor. I also haven't changed my driving habits, just back and forth to work less than 10 miles daily.

I guess we will see once I change the sensors and redo the exhaust in the next week or so.
 
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