1999 Dodge Durango Misfire

Hello all,

i have a 1999 dodge durango with the 5.2 i believe it is and it has developed a misfire. it is throwing a code that it is cylinder #4. it is getting spark and the plug isnt fowled or anything so i was just wondering what to check next and how to go about fixing it. speedy responses would be very much appreciated because my sister is taking this car to school in a few days and i need to have this fixed to get emissions tested. if you need more info i can try my best to fill you in more, but any input would be awesome! thank you so much!

Check for vacuum leaks, make sure that injector is working, make sure that injector is getting a signal, do a compression test, do a leak down test.

Make sure the plug wire is on tight at the dist cap. Swap a plug wire with another cylinder and see if the code moves. Do a compression test. Ohm out the injector on that cylinder. Put a noid light on the injector connector and wiggle all the wiring that's anywhere near it to see if the signal drops out. Check the condition of the terminals in the distributor cap.

Tune ups usually get ignored on these things since its such a pain to do, Ive fixed so many magnum V8's running bad with just a tune up that its pretty much the first thing I do.

^ +1. Tune up first.

These things are known for vac leaks underneath the intake manifold causing a misfire. There's a black 'plate' that bolts to the intake manifold underneath it. PITA to do.

I'd throw plugs in it, make sure the wires/cap/rotor are good, and drive it around very easy on the gas and hope the computer monitors will set so you can get an inspection sticker on it.

Easy way to check for the plate leak: Unplug the pcv line and the hose going to the breather on the other valve cover. Hold your fingers over both while the engine is running and see if the crankcase develops a vacuum.

Generally you get super ---- mileage and oil loss from that leak as well.

They are also known for a misfire due to rings/valve seals. I know you said it wasnt fouled but its pretty common. Youd likely notice it though. For some reason most ive seen were cyl #7? lol

Also check the wires, they can easily hit the exhaust manifold.

Yeh, i have a high miles magnum 3.9 (basically same motor) that gets misfire codes with none of the things i mentioned wrong with it. I forgot about that. Once the check engine light has been on for 2 or 3 yrs you kinda forget which codes it has!

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Originally Posted by Vigo

Easy way to check for the plate leak: Unplug the pcv line and the hose going to the breather on the other valve cover. Hold your fingers over both while the engine is running and see if the crankcase develops a vacuum.

Generally you get super ---- mileage and oil loss from that leak as well.

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I was told to open the throttle butterfly and look to see if the plate beneath it is oily. I think your idea is a lot better!

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Originally Posted by Orangetona

They are also known for a misfire due to rings/valve seals. I know you said it wasnt fouled but its pretty common. Youd likely notice it though. For some reason most ive seen were cyl #7? lol

Also check the wires, they can easily hit the exhaust manifold.

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Speaking of, I have a 5.9L that likes to throw codes P0300, P0301, P0303, and P0307 quite frequently. Are valve seals pretty common? I replaced the passenger side head with a spare when I got the engine as the original head had a spark plug stuck in it. I'm wondering if I should replace the driver side head as well.

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Originally Posted by turbodaytona87

Speaking of, I have a 5.9L that likes to throw codes P0300, P0301, P0303, and P0307 quite frequently. Are valve seals pretty common? I replaced the passenger side head with a spare when I got the engine as the original head had a spark plug stuck in it. I'm wondering if I should replace the driver side head as well.

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Well 1, 3 and 7 aren't all on the same side, but the stock heads do like to crack. Diagnose it before taking it apart, we've given you idea's on what to check.

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Originally Posted by turbovanman

Well 1, 3 and 7 aren't all on the same side, but the stock heads do like to crack. Diagnose it before taking it apart, we've given you idea's on what to check.

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WAT?

I've got an M1, no leaky plenum there. Injectors have been swapped around, no change on cylinder misfire. Plugs are new, wires are new. Tried swapping coils. Tried replacing MAP and TPS. Fuel pressure tests good. Vacuum is decent (18-19")

1,3,5 and 7 are on the same side, 2,4,6 and 8 are on the other side as well, just like a chevy engine, it's fords that run in order; 1,2,3,4 on 1 side and 5,6,7,8 on the other.

I know, I was just surprised to her him say that.

I'd still get a can of carb cleaner and check for vac leaks.

LOL yeah definitely all on same side. Sounds to me like a vac leak is more likely. Being that its 3 cylinders.

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Originally Posted by turbodaytona87

WAT?

I've got an M1, no leaky plenum there. Injectors have been swapped around, no change on cylinder misfire. Plugs are new, wires are new. Tried swapping coils. Tried replacing MAP and TPS. Fuel pressure tests good. Vacuum is decent (18-19")

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Hahahha, oops, my bad.

So yeah, it sounds like a head problem. We had a customer with one bank random misfires, removed his heads and that side was cracked, valve grind on one head, replaced the other, fixed.

Yeah I might swap it sometime. I think I want to check the wiring harness first though, the computer seems to have weird readings for some sensors.