Cylinder 3 Misfire

[Rdeitz]

I have the code for a Cylinder 3 misfire. Plug good. Wire good. Replaced the coil pack, still there. Replaced the injector, still there. Jeep is a 2001 Wrangler, 4.0 with 20,000 miles on it. I have heard it is probably the valve springs. Anyone here have that issue and that's what the problem was?

 

[Rdeitz]

OK I replaced the valve springs on number 3, drove it for while to heat it up (freeway). So I replaced the injector, coils, valve springs on number 3. Still shows misfire. The engine runs fine, no loss of power, no back firing, seems normal. This just a secret code they inserted to have you bring it into the dealer and they clear the light for $300? New plugs, wires, engine has 20,000 miles on it.....

 

[chimmike]

Have you checked the exhaust manifold gasket? Exhaust manifold itself? What about the injectors?

 

[Rdeitz]

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Have you checked the exhaust manifold gasket? Exhaust manifold itself? What about the injectors?

 

[Rdeitz]

Replaced the injector on number 3, cleaned the others while doing that. Manifold and other parts still look new, the Jeep stays in a garage and has 20,000 miles on it. No loose bolts.

 

[Jerry Bransford]

Probably the notorious #3 cylinder fuel injector heat soak issue that Jeep issued a TSB for. It's fixed by nothing more than wrapping a piece of insulation around the #3 injector and holding it in place with a small zip tie. Without the added insulation the fuel inside the #3 injector vaporizes when the area around it gets hot.

This is the insulation Mopar specifies for that fix.

https://www.amazon.com/gp/product/B007O3QHDK/?tag=wranglerorg-20

 

[Rdeitz]

Just ordered it.......

 

[pagrey]

The mopar kit is a bit overpriced. I just did mine and used this thermo-tec stuff. It works really well and you can do the whole fuel rail.

 

[Rdeitz]

Just ordered it.......

of course they also issued a TSB on those valve springs.....

 

[Rdeitz]

The mopar kit is a bit overpriced. I just did mine and used this thermo-tec stuff. It works really well and you can do the whole fuel rail.

View attachment 278785

It was $11. I can live with that.....

 

[Jerry Bransford]

of course they also issued a TSB on those valve springs.....

Not for a 2001, that TSB was only for the first couple years of the TJ.

 

[pagrey]

This cost less, that's all I was getting at. Either work and I saw the ship had sailed, really just posted so other people see there are other options.

 

[Wtrask]

Try using sea foam. You may just have carbon buildup on the valves. Or maybe a bad injector. I’ve had both issues. I doubt it’s mechanical.

 

[Jerry Bransford]

Try using sea foam. You may just have carbon buildup on the valves. Or maybe a bad injector. I’ve had both issues. I doubt it’s mechanical.

The #3 cylinder misfire is a well known problem caused by fuel vaporization inside the #3 injector in warm-hot conditions. That's why Jeep issued the TSB specifically and only for the injector for the #3 cylinder where his misfire is located.

 

[Rdeitz]

Try using sea foam. You may just have carbon buildup on the valves. Or maybe a bad injector. I’ve had both issues. I doubt it’s mechanical.

I replaced the injector - it's new.

 

[chimmike]

Having the exhaust manifold right under the intake manifold is doing us no favors for heat control, haha.

 

[Jerry Bransford]

Having the exhaust manifold right under the intake manifold is doing us no favors for heat control, haha.

That's the usual configuration for a straight-six. Insulating the #3 injector fixes the problem in about a minute.

 

[chimmike]

That's the usual configuration for a straight-six. Insulating the #3 injector fixes the problem in about a minute.

Eh, it may have been on designs 40+ years ago. Most slightly modern straight 6's aren't. BMW, Nissan, Toyota at least.

 

[JKP]

Having the exhaust manifold right under the intake manifold is doing us no favors for heat control, haha.

Leftover from the carb days when the heat kept fuel from the carb from puddling in the intake.

V8s used to route exhaust through the intake to heat it.

 

[bromel]

Sometimes a cracked 0331 cylinder head can present with a #3 misfire. You aren't losing coolant, right?