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v6 Magnum 3.9L engine ticks under load? (video)

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Old 07-22-2014, 12:00 AM
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Default v6 Magnum 3.9L engine ticks under load? (video)

I assume this is the pinging everyone talks about, but I hope it isn't since I've already done:

- The cooler autolite plugs
- Several rounds of seafoam
- Several rounds of injector cleaner

It happens at partial throttle under load, usually about 2 minutes after it's started cold.

To help out I stuck my little video recorder under the hood and went for a drive, you can hear it when I accelerate at 2:20 mark and maybe before.


I bought the truck just before the July 4th holiday weekend from state surplus with 169k on it.

Thank you in advance! I've been lurking on here for a while and you guys have excellent write ups for maintenance and fixin'!

I will confess ignorance to these engines since my other car is a Jeep with the 2.4L PowerTech, although there are some similarities outside of the motor.
 

Last edited by Jeepguy05; 07-22-2014 at 12:07 AM.
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Old 07-22-2014, 12:53 AM
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I don`t have any experience with the V6, but im not really hearing anything unusual from the engine. When you got the truck did you get any service records with it ?.


If not, start with a complete tune up. Plugs (already done), plug wires, cap/rotor, 02 sensors, air filter, and go from there. Maybe some one else can hear something in the video that I may be missing.
 
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Old 07-22-2014, 08:57 AM
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Ram Driver: nope, surprisingly enough the State didn't give me anything, including info about the infamous plenum replacement. Only thing I got was the windshield sticker for recent oil changes that show me it's only had 2,000 miles put on it in the last few years. The wires look newer so they might be OK, but the coil appears to be OEM and a little rusty. I actually went through 2 sets of plugs already, the first set were the recommended copper plugs (autolite 5224?) and after reading here I switched to the cooler ones. Last plug near the brake booster was a bear to get out, they never changed it I'm guessing. Plugs I pulled out were the factory label Champions that all had a gap of around .85" from age I guess?


A few more addons:


It idles a little rough for my taste, although 700 RPM is the correct speed I believe.


I bought it with the P0132 and P0138 codes set (both o2 sensors), after clearing only the 138 came back so I pulled the rear o2 sensor which appeared to be OEM and the probe was bent, so I replaced it with a Bosch from autozone. Didn't see until after installing it that I shouldn't have bought that brand, I assume they'll exchange but I will wait to see if the 138 code comes back.


The ticking sound could be normal for all I know, as you can hear in the video there's an exhaust leak somewhere and the tick might not be audible if it was piped right.


With 169k I'm ruling the plenum out as being a problem since it had full oil at purchase and I changed it immediately and it's still full. Haven't done the magnet or mirror tests just yet.
 

Last edited by Jeepguy05; 07-22-2014 at 09:06 AM.
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Old 07-22-2014, 09:36 AM
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Have a look at the plenum before ruling it out. The serious vacuum leak it can generate will make you run lean, and lead to spark knock. (pinging)
 
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Old 07-22-2014, 09:58 PM
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I thought I could hear a little bit of an exhaust leak, so that would be something you would want to get fixed. If both 02 sensors are original, with 169,000 miles on them there both bad. They are supposed to be replaced every 60,000 - 70,000 miles. Don`t use Bosch 02 sensors.


As HeyYou said above, don`t rule out the plenum, at 169,000 miles it needs to be done.
 
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Old 07-23-2014, 10:48 PM
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Well it failed the magnet test (it sticks).

Mirror didn't help me any, but a flashlight and smartphone camera took some decent pictures. All I see is dried oil possibly but you pros might see more:















And also now that I look closer you can see where I drug the magnet across the plate.
 

Last edited by Jeepguy05; 07-23-2014 at 10:51 PM.
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Old 07-23-2014, 10:55 PM
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From what I see, you need to fix the plenum. I don`t see any pooling of oil, but there is more oil in the plenum than there should be.
 
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Old 07-24-2014, 01:47 PM
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I'd have to pay a small shop to do the repair since I'm not comfortable with it, so are there more tests to confirm this is what's causing the ticking before I drop the big bucks?

If the tick is from it running lean I assume the long term consequnces are very bad for this engine.
 
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Old 07-25-2014, 06:00 PM
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Well now I'm pretty sure the plenum gasket isn't blown because I tried a few gauge-less tests mentioned on the forum and it seems like I have plenty of vacuum.

After replacing the downstream o2 my p138 code has stayed out for almost 100 miles. I did get the P0301 cyl1 misfire but the light went off for that after another 20 miles.

Something interesting I saw though was that pouring windshield washer fluid (winter formula with methyl) into the intake helps clean with a seafoam-like effect. Anyone tried this?

My idle is still a little rough and dances around 700rpm in drive, and the ticking persists. Next I was planning on replacing PCV with an official Mopar one and doing the coil.

The P0132 code that was originally set when I bought the truck hasn't come back, but I'm wondering if replacing the pre-cat upstream o2 will stop the ticking? It sounds like on the forums that the first one is used by the engine to make lean/rich decisions.
 
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Old 07-25-2014, 09:10 PM
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Ok, so now your trying to destroy your engine by pouring water into it ?, that's a great way to bend a rod, because water doesn`t compress. At 169,000 miles, any member here would tell you that replacing the plenum gasket is a must do at this point. either way though its up to you.


It is also recommended that you replace the timing chain also.
 

Last edited by Ram Driver; 07-25-2014 at 09:39 PM.


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