5.9l Misfire

[pacofortacos]

Remember a miss could be a dozen things. What led me to finding mine (as it was relatively an unheard of failure) was I did everything and came to the conclusion that it was a mechanical issue.

Compression test showed a couple of low cylinders, the air test indicated exhaust valve.
Even after I pulled the heads, I didn't see the problem (saw the cracks but like I said they aren't an issue). It wasn't until I removed the springs and moved the valves by hand that I saw the issue.
There were actually more bad seats than low compression cylinders.

By the time that I got rid of the truck, number 8 cylinder was getting tired and needed rings.
But it had a couple of hundred thousand miles and was run hard for many of them.
But with the right plugs, tune up and tune the 5.9 can run really well on 87 octane fuel.

 

[pacofortacos]

Lol, I went through a few trans rebuilds even with a deep aluminum pan and heavy duty external cooler.

My ideal truck would have the 5.9 w/8 speed trans

 

[Braeden Clark]

Remember a miss could be a dozen things. What led me to finding mine (as it was relatively an unheard of failure) was I did everything and came to the conclusion that it was a mechanical issue.

Compression test showed a couple of low cylinders, the air test indicated exhaust valve.
Even after I pulled the heads, I didn't see the problem (saw the cracks but like I said they aren't an issue). It wasn't until I removed the springs and moved the valves by hand that I saw the issue.
There were actually more bad seats than low compression cylinders.

By the time that I got rid of the truck, number 8 cylinder was getting tired and needed rings.
But it had a couple of hundred thousand miles and was run hard for many of them.
But with the right plugs, tune up and tune the 5.9 can run really well on 87 octane fuel.

Well if I do end up getting this truck I probably will start with a compression test. Get the worst possibilities out of the way and pray it's not that. The engije only has 133k

 

[pacofortacos]

If it is clean and priced right (aka would it still be a good deal after putting money into it) it might still be worth it.

 

[pacofortacos]

Well if I do end up getting this truck I probably will start with a compression test. Get the worst possibilities out of the way and pray it's not that. The engije only has 133k

That's not bad mileage. More amazing is that it is rust free being a PA truck.

 

[Braeden Clark]

That's not bad mileage. More amazing is that it is rust free being a PA truck.

Yea if its got a spec of rust on it I'd probably pass but it looks really clean and the guy says it is. He claims the only issue is the running rough until about 2500 rpm. Finding a rust free truck is almost unheard of in my area so I feel it could be a good deal. I should be fine putting money into it as long as I can sell my Jeep for a good bit. That is if the trans on the truck is ok for a while...

 

[pacofortacos]

In stock form (motor) and not used with heavy towing, the trans is fairly dependable. There is an anti drainback check valve in the trans line that has been known to fail and cause problems.

My 16 has the 8 speed trans and it is sweet. I would take the 5.9 over the hemi for my use though but the ZF 8 speed is much nicer than the 46RE trans.

 

[Braeden Clark]

In stock form (motor) and not used with heavy towing, the trans is fairly dependable. There is an anti drainback check valve in the trans line that has been known to fail and cause problems.

My 16 has the 8 speed trans and it is sweet. I would take the 5.9 over the hemi for my use though but the ZF 8 speed is much nicer than the 46RE trans.

I really wish the manual trans was more common because I would MUCH rather have that. But they are hard to find

 

[Braeden Clark]

In stock form (motor) and not used with heavy towing, the trans is fairly dependable. There is an anti drainback check valve in the trans line that has been known to fail and cause problems.

My 16 has the 8 speed trans and it is sweet. I would take the 5.9 over the hemi for my use though but the ZF 8 speed is much nicer than the 46RE trans.

Do you know the absolute cheapest aftermarket head for the 5.9 that fixes the cracking problem?

 

[Bear_Gibson]

The cracks really very seldom cause any issue, it's the exhaust seat itself that fails, but happens more often if tuned and running really loaded and even then it really isn't that common on most trucks.
I was tuned and tow a boat from Pa to Fl - the 5.9 ran better than most. Even then it was over 100k miles when it failed.

Mine is Tuned, and I tow a boat.

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[Bear_Gibson]

Cracked? Yes, most often it won't do anything.
IMO the only option is new heads, other option would be to put exhaust seat inserts in but it isn't cost effective.
New heads probably $500-1000 all in if you do the work.

Are you referring to the EQ redesigned heads?

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[pacofortacos]

Eq is one of the brands. There are several.

I put on EQ's but the ports are larger and it just didn't have the low end power of the stock heads after the EQs.

I was going to try CIFIC Auto heads and bought them, but traded the truck before installing. They used stock sized ports w/hardened seat inserts - the machining looked nicer than EQ.

EQ heads are a bit pricey now, almost to the point that aluminum becomes an option.

 

[pacofortacos]

Mine is Tuned, and I tow a boat.

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I think in my case it was the distance, going over mountains and at 70+ mph year after year. Boat/trailer was probably 5000+ lbs., bed packed to the top, cab usually full. I traded the 2001 in 2016.

 

[Braeden Clark]

I think in my case it was the distance, going over mountains and at 70+ mph year after year. Boat/trailer was probably 5000+ lbs., bed packed to the top, cab usually full. I traded the 2001 in 2016.

Can bad injectors cause this misfire issues as well? If so, is there a link for some cheap replacement injectors?

 

[Bear_Gibson]

Can bad injectors cause this misfire issues as well? If so, is there a link for some cheap replacement injectors?

Absolutely, and it would be easy to test. Remove the safety clip that keeps the electrical plug from coming off. I believe its a metal clip on them then while its running unplug each injector to find it. You can also use a temp gun to Identify which cylinder by checking the exhaust manifold temps. Look for one that's lower than the rest

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[Bear_Gibson]

Listen to the engine when you unplug each cylinder. If it doesn't change then you found the dead cylinder.

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[Braeden Clark]

Absolutely, and it would be easy to test. Remove the safety clip that keeps the electrical plug from coming off. I believe its a metal clip on them then while its running unplug each injector to find it. You can also use a temp gun to Identify which cylinder by checking the exhaust manifold temps. Look for one that's lower than the rest

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Would I just unplug each injector until I find the one that doesn't change the misfire?

 

[Bear_Gibson]

Yes, just like pulling plug wires to look for a dead cylinder.

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[Bear_Gibson]

Theoretically, if you had an injector pigtail you could use a fuel pressure gauge to test each injector. Look for pressure drops when power is applied. I'm not sure on the voltage, but I'm sure a little research could shed light on that.

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[Braeden Clark]

Theoretically, if you had an injector pigtail you could use a fuel pressure gauge to test each injector. Look for pressure drops when power is applied. I'm not sure on the voltage, but I'm sure a little research could shed light on that.

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I guess the main thing that concerns me with this misfire is that apparently it doesn't go away until 2500 rpm. Does that point more towards an engine issue? Tps?