Engine loss of fuel after hard acceleration.

[Daveb]

Hey guys, I figured I'd post to see what you all thought. At completely stock power or with the edge comp all the way up, stock injectors and turbo or aftermarket, it doesn't matter, the truck will die after a hard pull if you take your foot off the pedal. It won't drop back to idle like it should. If you keep your foot on the pedal just a little bit for a couple seconds, it recovers and all is well. It sounds like it's running out of fuel. The airdog never drops below 12psi. The vp has about 3000k on it. It did it with the old vp too. I'd like to understand why if possible.

 

Thanks. 

[Mopar1973Man]

How many miles on the injectors?

 

[Daveb]

Not sure to be honest. They are DAP. The ones before it were stock ones with as much as 250 k and they were doing it too. 

[GSX455]

Is it throwing any codes ?  P1693?

I had my overflow valve on the VP44 go bad.   It would buck like its out of fuel under acceleration.   My fuel pressure stayed above 12 psi

 

[Daveb]

Brand new overflow valve with new pump. 

 

I do have codes just recently (engine light came on last week) but the issue was occurring prior to the engine light as well. 

[Daveb]

Just started driving home and now the throttle got a little buckey when I was accelerating. Just started. MAP sensor?

[Marcus2000monster]

Have you troubleshooted for the codes? 

[Daveb]

I just cleaned both sensors. They were not dirty. 

[Mopar1973Man]

Some is running Smarty Tuner? P0602 is a give away for ECM flash tuner. 

 

If you are not using a Smarty or similar tuner then your most likely going towards a failing ECM. If this is true then I would test for excessive AC noise issues.

6 minutes ago, Daveb said:

I just cleaned both sensors. They were not dirty. 

 

 

[Daveb]

Interesting. I have a comp box. The ac seems to be normal. No strange noises. Really? An ECM? Geez I hope that's not true if so what a pile.  

[Mopar1973Man]

 

If you got a dealer near you may try to have the ECM reflashed to see if that helps. Typically this a Smarty thing where people see P0602 error codes because the Smarty alters the ECM information. Since your not using a Smarty and the Edge Comp doesn't alter the ECM programming this means it took damage some how. The most common damage source is bad alternators. Typically people with Automatics tend to get the torque converter lock and unlock issue but wrap tin foil on the charge leads, add a noise filter to the PCM or add or relocate ground wires. Again this never fixed the problem just band aid the problem. So now the noise issue goes on to wipe out the ECM and VP44's. Even manuals like my truck have the AC noise issue but from what I'm learning is the grid heaters cause the failure of the alternator diodes which creates the AC noise issue. 

[jlbayes]

The hypertech and superchips will produce the P0602 as well. You may have an issue with the edge box based on what faults are there.

Edited March 26, 2018 by jlbayes

[Daveb]

well now that I think about it, mopar man mentioned the alternator as being a possible culprit, and one year/15k miles ago, I swear it was making noise. I think I should have that checked first, then clear the codes, and see what happens. On my way to work this morning I think I am losing my pedal. The thing starts and idles fine and drove fine for about 3 minutes. It started acting up and jumping like it didn't know how much to fuel it needed the rest of the way to work. It was like the pedal was jumping around.  Fuel psi held steady at 14. 

 

I'll see if I can clean it too. 

[Mopar1973Man]

50 minutes ago, Daveb said:

It started acting up and jumping like it didn't know how much to fuel it needed the rest of the way to work. It was like the pedal was jumping around.

 

Typical AC noise problem. Next time this happens pull the field plug on the back of the alternator if the problem goes away when the alternator is NOT charging then the alternator diodes have failed. What you post is a classic AC noise issue where the AC noise corrupts the tach signal the ECM varies the throttle up and down back the ECM is seeing the two waveforms. The dash cluster won't report it or show it on the tach but its happening. 

[Daveb]

Wow thank you I will check that!!

 

I know there are only a few wires on the alternator, I can research what the field plug is (guessing the only plug-type connector back there), and will then see what happens. You think it's safe to just pull over when this is happening and then disconnect it then continue on my way without shutting the engine off?

[Mopar1973Man]

1 minute ago, Daveb said:

You think it's safe to just pull over when this is happening and then disconnect it then continue on my way without shutting the engine off?

 

Yes. I've done it plenty of times when alternator failed badly so instead of taking AC noise damage to the electronics I shut down the alternator by unplugging the field lead and continued home on just the batteries. Typically you'll find out all the weird issues go away because now you are on "TRUE DC" power once again. The computers all start work perfect. 

 

The cause I'm finding is the grid heaters that kill the alternator diodes. I'm not clear on why yet but research the solution to this whole AC noise issue. 

[Daveb]

Wow, I'll check that out and let y'all know what I find. 

[Daveb]

Just left for lunch and unhooked it. No change. Starts and idles fine. Barely made it home for lunch. Acted like it was jumping all over the place. Totally erratic throttle. Just got home. Going to take the apps apart and clean it. Don't know what else to check at this point. Gonna be a long slow drive to the dealer. 

Well, I recalibrateed the apps and it did nothing. Starts right up and idles fine and occasionally will surge for a second out of nowhere once every few minutes. Then the pedal is all over the place. 

[Mopar1973Man]

1 hour ago, Daveb said:

Going to take the apps apart and clean it.

 

Don't do it. Just replace it with a Timbo APPS. There is nothing to clean.

 

1 hour ago, Daveb said:

occasionally will surge for a second out of nowhere once every few minutes.

 

ECM issues. You can verify this with a live data tool and monitor the TPS signal. If the signal jumps then the APPS to blame if the signal is steady then the ECM is to blame. Still at that rate test the alternator for AC noise. 

[Daveb]

Well, true dat. All I can do is test that and the IAT and MAP while I'm at it. May as well test the engine crank sensor too.  If it is the ECM this thing is a real POS. I take such good care of it. Now I'm starting to get scared that I'll be able to make it home while out in the UP.  Wondering if it's not a reliable year to own. Seems like you're happy with your 02. 

 

Enough speculating. I'll test everything and see what happens.