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4.0 sohc feels low on power


sgtsandman

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I put the whole bottle in right after I said that lol. I noticed while I was driving it that it would rev freely up to about 3k then suddenly stop pulling. This makes me think that it isn’t getting the fuel and air it needs. Any thoughts
One step at a time. If you do a bunch of stuff and throw the parts cannon at it, you won't figure out what the problem was and will have no idea what fixed it.
 


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One step at a time. If you do a bunch of stuff and throw the parts cannon at it, you won't figure out what the problem was and will have no idea what fixed it.
Fair enough. I started and listened to it with the hood open and heard a rattle/ ticking noise. Not real loud, but definitely there. I compared it with timing chain chatter on YouTube and it was much quieter.
 

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Fair enough. I started and listened to it with the hood open and heard a rattle/ ticking noise. Not real loud, but definitely there. I compared it with timing chain chatter on YouTube and it was much quieter.
Just means it hasnt gotten bad yet though.

Unless the timing has slipped a tooth the chain/guide being loose shouldnt cause what youre describing but if you think thats an issue it needs to be addressed before it does grenade.

If its ok at low rpm but drops off up high id say its a fuel pump/filter or plugged cat.

Changing the filter is a good idea regardless but if that dont take care of it id diagnose it with a fuel pressure gauge and vacuum gauge
 
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Just means it hasnt gotten bad yet though.

Unless the timing has slipped a tooth the chain/guide being loose shouldnt cause what youre describing but if you think thats an issue it needs to be addressed before it does grenade.

If its ok at low rpm but drops off up high id say its a fuel pump/filter or plugged cat.

Changing the filter is a good idea regardless but if that dont take care of it id diagnose it with a fuel pressure gauge and vacuum gauge
I might do the timing tensioner change since I’ve read it’s not too difficult. I’m also gonna look into the fuel filter. Could it be the air filter restricting air flow?
 

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I might do the timing tensioner change since I’ve read it’s not too difficult. I’m also gonna look into the fuel filter. Could it be the air filter restricting air flow?
Hold it up to a bright light. If you can see light through the filter, it's good. If you can't see any light, it's way over due being changed.
 

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.i have a weakness that i generally assume .... the very first thing one will do..... is pull and read the plugs and check the gap.....because it is free. if they are not obviously wasted maybe just pushing a 60- 70 or more gap...usually brushing em off with a brass wheel and a regap will let you know right away if that was the problem...as your power will be back...

you can put brand new cats and o2 sensors in it...and fawk them up in a handful of tanks of fuel with shitty plugs...

from there the trouble shooting starts.
 
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I haven’t found a solution to my problem yet. Tried to do the fuel filter yesterday but decided not to after I sprayed half a gallon of fuel on the floor while I was the only one home. I had followed the steps ( take out fuel pump relay and start the engine to clear the lines). I’m gonna try again when I have others around to help me. I’m also looking into getting new timing chain tensioners as I have 187,000 miles on the truck and I don’t think they have ever been done. After that the plan is to check out the entire fuel/ intake system, as I think there is a problem with it limiting engine rpm and power
 

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Installing new cam timing chain tensioners is a good idea but it is highly unlikely going to solve your low power problem.

The fuel filter can cause low power by restricting fuel flow.

I had a low power issue at around 225K miles that ended up being clogged cats. One of the precats started breaking up and plugged the front main cat. I suggest you do some diagnostics for restricted catalytic converters, if installing a new fuel filter doesn't solve your problem.
 
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Installing new cam timing chain tensioners is a good idea but it is highly unlikely going to solve your low power problem.

The fuel filter can cause low power by restricting fuel flow.

I had a low power issue at around 225K miles that ended up being clogged cats. One of the precats started breaking up and plugged the front main cat. I suggest you do some diagnostics for restricted catalytic converters, if installing a new fuel filter doesn't solve your problem.
[/QUOTE
Sorry, I wasn’t very clear in that last one I wrote. I don’t expect the timing chain tensioners to fix the problem of low power, but I would still like to do them as the truck has never had them done, and I can hear a slight rattle. hopefully I can get done before it’s too late. I don’t have to replace the timing guides. How do I diagnose a clogged cat?
 

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So the plugs were good and gap was on?
 

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6 weeks on.....
You check clogged exhaust / cats with a vacuum gauge.

Also, the fuel filter replacement instructions I read included having the tank near empty as fuel can siphon out.
When I pulled my fuel pump fuse, the engine died immediately.
 
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6 weeks on.....
You check clogged exhaust / cats with a vacuum gauge.

Also, the fuel filter replacement instructions I read included having the tank near empty as fuel can siphon out.
When I pulled my fuel pump fuse, the engine died immediately.
Thanks. It actually was a clogged exhaust. What happened was the 3rd cat broke apart for some reason, and all the little particles from #3 flowed down with the exhaust and clogged up #4. To fix it I had the 3rd cat replaced with a universal Magnaflow and the 4th cat was cut out and had a straight pipe put in, as there are not o2 sensors behind it so its not needed for emissions.
 

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I had the 3rd cat replaced with a universal Magnaflow and the 4th cat was cut out and had a straight pipe put in, as there are not o2 sensors behind it so its not needed for emissions.
Glad you got it fixed. You ain't from California; that's for sure.
 
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Glad you got it fixed. You ain't from California; that's for sure.
Yep. Don't get me wrong, Cali is beautiful, but the politics and policies aren't ideal. I live in eastern Washington so I don't have any emissions crap to deal with thankfully.
 

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