Got this truck not too long ago, when I got it, it had a check engine light for 2 things, TPS sensor, and another sensor I forget the name of, but is vacuum actuated. After replacing those 2 my check engine light went away but I'm still getting a really rough idle. Too rough to just be engine mounts, but they are definitely getting torn up from the shaking. The ticking that kind of sounds like a misfire is because of a crack in the exhaust manifold, not sure if that could cause an idle this rough by tricking the egr system? Plugs and wires are new as well as all of the normal matenince stuff, only other thing I can think of to replace is injectors but wanted to see if anyone else had this problem before I put money in the wrong places. It's not a surging idle like I've seen some people have with their 5.8's and 302's, the rpms stay pretty steady but it just shakes the whole truck like crazy. I will post a video of the shaking below. Oh yeah, I also thought maybe 1 cylinder was low on compression, I didn't do a compression test yet so I'm not 100% certain, but I put a bottle of engine restore in it, everyone that I have seen use this stuff it solved all of their low compression issues. With it in the engine now there is not the slightest difference in the way it runs.

 

https://youtu.be/6HhjgeSOaso
Here is a video of how much it shakes.

 

That exhaust leak may be your problem,air entering the exhaust plays havoc with the o2 sensor.

 

Hopefully that helps it, I'm pulling the manifold off now to see if I can weld up the crack in it for now

 

You may have to perform the compression check to prove you don't have an issue.

Check your plug color while there are out.

Check your plug wires for any wires crossing over others.

 

The only thing this Snake Oil will do is clog your lifters a little more than they are already.

 

I did a compression test recently and all of the cylinders are within 90-105 psi, which is pretty low. Guess it's time for a rebuild haha

 

That about 30% wear and tear since 1989, you have fairly even wear.
Is it smoking at all ?
How did the new spark plugs look ?

Exhaust leak fixed yet?

 

Spark plugs looked great, no smoke whatsoever, none of the plugs looked burnt at all, just one of them had a little oil on it, but I'm just assuming oil is getting passed that one valve stem seal, which is an easy fix. And nope, haven't gotten the manifold fixed yet, thought I'd do a compression test first to see the state of the engine, I thought those numbers were too low, seeing as some people have 5.8's with 140-170psi. Maybe they were just really well taken care of. Guess I'll buy a new manifold and see the results here soon.

 

Well, 140-170 on a new engine or new rings and a valve job maybe, but not on a 1989...
How many miles on your engine?

Your valves are probably leaking a bit, but if they were really bad you would get some backfiring.

You could use a better video, showing the entire engine compartment.
Doesn’t look like it is shaking much from your video, but hard to tell.

How does it run at highway speeds?

I would block off the EGR-Valve from the intake by sliding in a solid gasket made out of metal sandwiched in-between two regular gaskets.

 

Runs just fine at speed, hard for me to say how many miles, I have no clue how many times the odometer rolled over, could be 160k could be 460k. But I'll try blocking off the EGR along with a new manifold, and upload a new video tomorrow too

 

What RPM is the Idle?
Have you checked the timing?

 

It idles right around 600-700 rpms checked all of the sensors around the throttle body but haven't checked the distributor timing yet

 

Wouldn't hurt to pull the valve covers and check for slop in the rocker set-up, arms, push rods, etc.

 

Would it be worth it to try and solve all of the problems with the idle, or just rebuild it or find a remanned engine with the compression being as low as it is?