P0340_alternator has been changed

[Ready2Rockyou]

2006 4.6 running a 5.0 with 2009 Saleen 3V take-offs, Comp cams, Paxton intercooled, delete plates, new motorsport throttle body, 39 lb injectors and dual pumps.

I have changed the alternator and verified both cam sensors; and in addition the wiring looks fantastic. What I'm wondering is since I haven't had it on the dyno yet (yes, it's coming soon), could the mail order tune be providing too much fuel causing this condition? I'm asking as it almost feels like the motor is so rich it stumbles at low idle, and every so often, will throw the engine light on and the ensuing P0340 code. When I'm WOT the thing rips, but at idle she doesn't want to run too smooth....

Thoughts? Everything else seems fine.

Yes, I did a search and read all about the bad diode in the alternator, however I did not see this being asked. Maybe I'm way off here; but my gut usually isn't that far off.

Any help would be greatly appreciated.

Thanks in advance.

PS-Cecil County dragway opens this Friday!!

 

[TexasBlownV8]

Measure and actually watch the voltage. It ay idle at around 14v (like it should) but if the voltage is dropping down into the 12's, you'll get a P0340. You have no visible way of really knowing (the 'voltmeter' on the instrument cluster is a dummy light).

When my car started occasionally throwing P0340 codes, it would drop voltage when running to the point where the code would come up. By monitoring it (even via datalogging), you can see what is happening. If the voltage is staying up there around 14 and you got the code, the charging system/power feeds are not the problem.
(Yes you've changed the alternator, but you didnt mention with what. And, what loads are on your electrical system: lights, fans, pumps, stereo, etc. By measuring the voltage, you'll know if you're still having voltage issues.)

 

[Alfiedagr8]

What cams are you using?
Are you using the stock phaser?
Any modification to the phaser?

 

[TexasBlownV8]

...and, any mods to the tune to account for the cams or mods to the phasor's (like limiters or lockouts)?

 

[Ready2Rockyou]

Okay, I never data logged until now-and it's so easy I'm kicking myself in the ass. I selected battery voltage and a couple variables thru live link of the battery functions. From that it gave me alternator readings and battery readings. Alternator read 13.8 and the battery read 12.8 volts. No additional power drains other than the Motorsport dual pumps. The alternator is new from Summit racing, tuff stuff. The cams are-compu cams 127330. Stock phasers I believe (JDM 5.0 long block, 3V heads).
So, obviously I contact Summit and do a switch? Any other thoughts?

Thanks for the help also.

 

[TexasBlownV8]

Hm. Your battery voltage and alternator voltage should be the same. But not just that, you have to watch it awhile when running. It may fluctuate and drop.

When running, confirm that voltage AT the battery, across the terminals, is one of the values being logged. When running, even 13.8 is a little low. If the battery voltage is under 13 using a voltmeter measurement, either the alternator is not charging or the fuseable link is blown between the battery and alternator.

There's a "PCM Voltage" PID, at least as read and reported by the PCM. That's the value I was watching , and it would vary as much as 1-1.5 volts when the alternator was starting to flake out. Now with a new PA alternator, it stays at 14.1 +/- 0.1.

(And thanks for the kind words in your PM.)

 

[whiteman46]

had the same code replaced alternator and mine went away luckily... but just for humor i took it to a shop and the guy insisted on replacing my whole exhaust and re flashing my hard drive cause someone had "messed" with it and that was what was probably causing the problem... said my exhaust was "to much" haha asked him about the alternator and he said none of his diagnostics led him to that.. just some tid bit from a mechanic in north carolina !

 

[TexasBlownV8]

The last part says it all.

Usually p0340 is the alternator. Sometimes it can be other timing-related issues.
But exhaust? I'd have laughed so hard and left laughing.

 

[Alfiedagr8]

The last part says it all.

Usually p0340 is the alternator. Sometimes it can be other timing-related issues.
But exhaust? I'd have laughed so hard and left laughing.

Yeah u never heard of that? With bigger exhaust it lowers the back pressure causing the Phasers to
Over advance. Causing the p0340 codes we all get. There is a TSB bull-shh-ittt. Good info on there. The fix is to go to stock or add a perpetual valve.

 

[TexasBlownV8]

..well think back more through the cams and valves and springs...for backpressure to affect cam positioning, there'd have be be quite a bit of pressure, or huge pulses, to force an exhaust valve open, compress the spring, and thus take some pressure off of the cam (with a depressed rocker arm, it's not going to be in much contact with the cam), and then altering the spring tension of the vct spring. Chances are the rocker would come out and no longer contact the can nor valve (change a cam sometime and see how easily the rockers fall out if they loose cam lobe pressure).
Perhaps a clogged cat or major obstruction could cause enough back pressure to do that.

But less pressure on the exhaust (the opposite), keeps the rockers solidly against the cam with the springs keeping the valve closed tighter. Same as aftermarket stiffer springs, and those dont cause such codes.

I would think things like incorrect oil viscosity or oil pressure issues would have more of an effect than exhaust.

 

[Sprayin Blue 3V]

Gunna revive this. I'm throwing a P0340 code right now, directly after I put my BBR stage 1 cams in. I dont exactly believe in coincidence so I'm going to go ahead and throw the alt out of the equation. I checked voltage at the battery while running and got like 13.6v. I'm fairly confident that it is good.

I think I might have skipped a tooth on the passenger side when putting the cams back in. Would a skipped tooth cause a P0340 to show up?

 

[rford426]

I had p0340 was the alternator...Came back on 6months later (last friday) car died and just picked up my rebuilt alt this morning its the alt i bet

 

[Alfiedagr8]

Gunna revive this. I'm throwing a P0340 code right now, directly after I put my BBR stage 1 cams in. I dont exactly believe in coincidence so I'm going to go ahead and throw the alt out of the equation. I checked voltage at the battery while running and got like 13.6v. I'm fairly confident that it is good.

I think I might have skipped a tooth on the passenger side when putting the cams back in. Would a skipped tooth cause a P0340 to show up?

Yes. As well as broken timing chain components.


Sent from my iPhone using Tapatalk

 

[Sprayin Blue 3V]

I had p0340 was the alternator...Came back on 6months later (last friday) car died and just picked up my rebuilt alt this morning its the alt i bet

its not the alt.

Yes. As well as broken timing chain components.


Sent from my iPhone using Tapatalk

Yeah I'm pretty sure this is what it is. I'm gunna pull it apart and re do it. Thanks!