5.9 Magnum will not run right

Hello all, I have been a long time reader but this is my first time posting.
I have a 2000 Ram 1500 with a 5.9L Magnum engine. The truck is a 4x4 automatic trans with 214XXX miles on it. It will start up and idle just fine on the initial start-up, but as soon as I start driving down the road it will bog like it is starving for fuel. When I come up to a stop the RPMs will drop to anywhere between 300 and 500 and then shoot back up to regular idle at about 650 when I come to a complete stop. Recently, it has also intermittently started backfiring out of the manifold under load, however it doesn't always do this.
I have replaced the TPS, the IAC, the MAF, the throttle body, redone all of the gaskets on the manifold, including the plenum, also replaced the water pump and thermostat while I had it torn apart. It has a brand new cap, rotor, plugs, wires, and ignition coil as well. I will be replacing the O2 sensors as soon as I get my new exhaust in, hopefully this weeked. When it originally started losing power it seemed like a plugged up cat, so I deleted it and am putting in a flowmaster high flow cat with new O2 sensors.

On a side note, I've read that backfiring out of the tb can indicate a lean condition, is that correct? I also pulled all of my plugs and they where bone dry and white.

Anybody with any ideas of what could be causing this would be greatly appreciated!

Might have skipped a tooth or two, have you tried advancing the timing a smidge?

I was under the impression that timing on these engines could not be changed without a PCM tuner... is this not correct?

I very well could be wrong and I'm sure I'll be corrected but if you have a distributor then you can turn it slightly to either advance or retard the timing. But if it jumped teeth then it's going to need some work on the timing system to get you going again. I.e. New sprockets, chain(s), tensioner, etc.

All right, thank you I’ll look into that if the O2 sensors don’t solve my lean problem. Also, I forgot to mention once I get at 3000 RPM‘s opens up and runs like a champ


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SYKRAMMAN said:

I very well could be wrong and I'm sure I'll be corrected but if you have a distributor then you can turn it slightly to either advance or retard the timing. But if it jumped teeth then it's going to need some work on the timing system to get you going again. I.e. New sprockets, chain(s), tensioner, etc.

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They are PCM controlled for timing. There is no adjusting at the distributor.

Yeah umm now I'm stumped, if it was a timing issue then it would be rough throughout the rpm's. You said you don't have a cat anymore?

Gr8bawana said:

They are PCM controlled for timing. There is no adjusting at the distributor.

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O,ok, yeah I wasn't completely sure what year the pcms came into play with the timing.

At the moment no, but it was bogging before I cut it out to try and fix it. Like I said I’ll be putting a full exhaust with new O2 sensors on this weekend.


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wait n see what some other folks have to say, you'll get it figured out soon with the knowledge of the members. Gl.

Have you checked fuel pressure? Could be a pump going bad. Need to check at idle and under load.

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I checked at idle when it first started doing it, I don’t remember the value but I believe it was in normal range. What’s the best way to test under load?


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Rest of my exhaust is in today, planning on installing it tomorrow and I’ll check the fuel pressure when I do that. I’ll let y’all know the results. Thanks for the help so far guys!


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Check it at idle and then rev it up to 2000 rpms. See if it drops off.

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So new exhaust is in, shorty headers flowmaster cat and cherrybomb extreme duals. Also put new o2 sensors in and swapped the plugs, so far so good no stumbling or stalling!


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RedDodge said:

So new exhaust is in, shorty headers flowmaster cat and cherrybomb extreme duals. Also put new o2 sensors in and swapped the plugs, so far so good no stumbling or stalling!


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Click to expand...

Glad to hear you got it sorted!

Take it back, drove it around more and it is not fixed. With new o2 sensors continues giving P0132 code and still chugging and bogging occasionally. Currently testing the circuit for the o2 sensor wiring, any other ideas would be greatly appreciated.

Let's think about this, runs fine with no load. Start driving apply load seems like it is starving for fuel. Is there a serviceable fuel filter? Think about it, maybe google. No its a sock on the fuel pump. Where would the fuel pump be? Maybe in the tank in the fuel tank. You got it, start there....

That is where I'm looking next because I'm running out of ideas, but if it was the fuel pump then why would it wake up after I got it up over 3000 rpms? I'm just confused about that part, but ill be looking at the fuel pump hopefully this weekend anyway. Thanks.

Curious was it the fuel pump? I’m in the same boat you were with my truck. I’m at my wits end.