AEM troubles

Hey Folks!
I have a 426 gen3 hemi managed by the MP AEM grey box (part# P5153528). I just crossed about ~3k miles on the brand new motor and it was running GREAT. I was slowly dialing in the calibration but some gremlins began to expose their ugly heads and finally took the system down! Here's the story...

With about 500 miles on the fresh build we were making the 800 mile trek to Mopars at the Strip in Vegas and the car shut down like a switch about a 1/3 of the way into the trip in the middle of the Nevada desert (!!!). We were just cruising along at 75mph (2100rpm), engine temp was 180, and everything seemed normal and fine. We coasted to a stop, checked for the obvious things (leaks, voltage, fuel pressure, etc), and nothing appeared suspect. Turned ignition on, heard the fuel pump activate, and the motor fired right back up, so we went on our way (nervously of course). This happened again another 300 miles down the road and once on the way back. Then it started acting up while driving around town when fully warmed up; engine would start and run for a bit then die. During this bout with car not running and ignition on, I moved my attention under the dash and could hear the main ECM relay in the fuse box clicking on/off rhythmically and the relay felt very warm. I turned ignition off then on again and fired it back up and got me home with no issues.

Last weekend in the middle of a 150 mile mountainous drive to a car show it turns off again. This time I shifted into neutral, turned ignition off then back on, and let the clutch out in 5th to roll start it, hardly breaking my pace (I was getting this down now). It started acting up again driving through the destination town, and finally right before the cruise it "switched off" for the last time and didn't come back. When I turned the ignition on this time, I couldn't hear the fuel pump activate at all. Again, all the usual checks revealed nada. Then I connected a laptop to the ECM and I could tell it was trying but just couldn't establish the connection. Usually when I connect to to the ECM via laptop a progress bar shoots across, the ECM firmware version displays, and the tuning dashboard pops right up. That the fuel pump isn't activating and the ECM isn't staying alive long enough for the laptop to connect, I'm thinking that the ECM went bad. I tried swapping around the relays, unplugging/replugging in the ECM (while power was off of course), and tested the power and grounds of the pin receptacles in the ECM connector (all good there). I even opened up the box to look for fried components or toasty smells. Here is screenshot of the software trying to connect to the ECM...


I was thinking the box may have been overheating since the failure happened after the car has been running awhile, but the installation instructions say to place it in the interior and not be exosed to temps >257F. I have it installed behind the dash secured on top of the bracket above the steering column. There's no way its gets close to that hot in there. Anybody have any ideas? I wish I had another unit to test with. Along those lines, I'd be very interested in picking up another MP AEM box (P5153528) if anyone has one laying around they're not using. It looks like this...

Otherwise I'm afraid my only other option is to consider going a whole other EFI route: factory DBW, FAST/XFI, etc.

It almost sounds like a flaky connection somewhere, but you'd think it would show itself more consistently than that. The fact that it usually starts right back up is the weird part. Have you tried again after it has been sitting for some time? I suppose there could be some electrical component that just doesn't deal with heat anymore and is breaking down internally. I've had two motorcycles with ignition issues that would manage to keep running if it failed while driving, but as soon as the bike died you couldn't get it restarted because it killed two cylinders. I'd ice down the suspect component with a spare can of freon (maybe not the best plan, but it was what I had on hand), and it would light back off. Trying to think if there are any other tests that come to mind. I guess if possible you could try icing down the computer if your harness is long enough to get it out from under the dash to see if it's something failing when it gets hot.

If I remember correctly Tincup had a similar issue with his shutting down. He was using a factory box but I believe the issue was the same. I also think a new ECM was the cure

toplscuda said:

If I remember correctly Tincup had a similar issue with his shutting down. He was using a factory box but I believe the issue was the same. I also think a new ECM was the cure

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Hmmmm, I seem to remember it being a bad Crank Position Sensor. In Cruizin's case I think his problem is a bad ECM as he is unable to get his laptop to recognize the ECM.

One of the things that I would ALWAYS look at when diagnosing a problem with EFI is the grounds. I'd make absolutely sure that I had EXCELLENT grounds for all sensors and the ECM. A bad or intermittent ground can cause a lot of havoc.

Regards,

Joe Dokes

Thanks for the responses guys, those are great suggestions! I'm suspicious that heat may have caused the issue but I know that it's not maintaining it, if that makes sense. I went through the whole round of troubleshooting the day after the car was towed, in other words everything was completely cooled down. I would also suspect bad grounds but the grounds (and permanent & switched 12v) on the connector all test good and solid, ECM still won't come back to life. To give some background, I way overbuilt the grounds on this car, lol! I have a 00 ground cable from battery (in trunk) to the shock mount bolt (superfluous now with 4 link) on bare metal, star washered, and painted over, grounding the chassis very well. Further up another 00 cable connects a stud/bolt in the frame (similarly prepped) to a bell housing bolt (into rear of block), which the EFI system ground is also star-washer sandwiched to. Just to be sure I also grounded the front left cyl head to the AlterKtion frame via 8ga cable.

One other thing left to try is doing a "pull through" test on each receptacle in the ECM connector with a dental pick or something similar or smaller size than the ECM pins to ensure each pin is making contact when the ECM is plugged in.

In the meantime I'm on the hunt for another ECM:
Want to Buy AEM (Mopar Performance) grey box P5153528!!! Please let me know if you, or anyone you know, has one to part with. Thank you very much!

Checking the pins for retention is a good idea. My brand new MSD box when I was first trying to fire my car had the pin lock loose on the connector. It wouldn't fire and I would get a bad cam sensor message on and off. Finally got smart and put a meter on the pins at the sensor (after buying a new sensor) to see what was up and found out one went nowhere. Followed it back to the MSD box and found out the pin had pulled out of the connector just enough to not be noticeable, but also not make contact.

Cruzin,
I have a brand new MP / AEM ECM still in the box. The programming I sent you came from this ECM. We should talk...

I'm abandoning the AEM system; MP no longer supports it and neither does AEM. Maybe if I could find a box quickly, and for very cheap (like <=$500), I would consider it. But fun driving season is just about here and I need to get this beast back on the road!

After a lot of research and consideration of other options (factory drive-by-wire, FAST, and Holley), I've decided to go with the MegaSquirt 3 Gold Box <http://www.efisource.com/shop/ms3-gen3-hemi-plug-play-gold-box/>. Here's why: it's the least expensive; the tuning interface looks very robust and powerful (Tuner Studio); the circuitry and processing are "open" and transparent; it's robust, scalable, and updateable; and most importantly there's an active community of users and developers, in other words this system isn't going anywhere anytime soon. A parallel in my IT world would be Linux/Unix vs Mac/Windows. Also, I get to keep my current cable operated throttle body which I have a lot of time invested into fabricating bracketry to operate smoothly, and I just like the idea of my foot directly controlling the power. I know I would be more on my own so to speak but there's a large community to support each other (like here on FABO) and I enjoy the challenge and the satisfaction of knowing my systems intimately, and so I can troubleshoot/repair stuff on my own down the road.

Thanks to all who've offered assistance. I'll update with another thread as I progress down this avenue...

That is the same system I plan on using for some of the same reasons. Just a couple grand shy of that right now
Subscribed. I want to see how your new system install goes.

Mike

Agreed, I'm anxious to see how you like the gold box setup as well. I have an MS2 I got as a takeoff from someone that used it on a 340. It's had its teething issues, but I think most of that might have stemmed from a bad relay board. I've since rewired pretty much the entire car with new quality wire and terminals and things work the way I always thought they should.

One last ditch effort (idea) is to send my AEM box to somebody with a known good system, swap it in, and see if they can connect to it. Does anybody else have this in an operable system and willing to test it for me?

Cruisin,
I've decided to sell my AEM box in favor of the Holley system. PM me or better yet, text me if interested.
Cuda SRT8

I have the Gold Box and it is solid, only problems I've had have been my own learning curve with understanding IAC vs my big cam. Everything above idle and cold start has been flawless.

72BBSwinger said:

I have the Gold Box and it is solid, only problemshows I've had have been my own learning curve with understanding IAC vs my big cam. Everything above idle and cold start has been flawless.

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Which "Gold Box" is this? The only Gold Box I'm familiar with is the old MP Orange, Silver and Gold ECUs for electronic ignition distributors

Cuda SRT8 said:

Which "Gold Box" is this? The only Gold Box I'm familiar with is the old MP Orange, Silver and Gold ECUs for electronic ignition distributors

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MS3 Gen3 Hemi Plug & Play Gold Box - EFI Source

Yep, that's the one. I ordered one from them early this week. Mike is a fellow Mopar nut, very knowledgeable, and great to talk to. I'll be updating as the installation progresses. 72BBswinger, it's good to have your feedback and nice to hear that it's working out well for you. I'm interested in your idle tuning issue as I'm anxious about that part too with my larger displacement (7L vs 6.1) and moderate cam (231/240 @ .05). Can the AutoTune function in Tuner Studio help with smoothing out the idle?

Yes it can but his installed tune was a little to aggressive in the timing dept for my combo so I had to change those tables quite a bit. My engine is 7.0L too, 420 cid. My cam is nasty 247/255 @ .050 and has very little vacuum below 1100rpm. You set your AFR targets from idle to 7000rpm and the autotune will then adjust the fuel table accordingly while you drive. Uchoog and I both run MS3 on our Gen III's and he has helped me a bunch and is who led me down the timing road with mine. I like mine with 14 degrees at idle I think he is in the 8-9 area with his, he is at sea level pretty much, I am at around 2300 ft. He has Hilborn with no IAC, I have 92mm TB, stock 6.1 intake and an IAC motor. You will also need to change the base settings for required fuel in tuner studio once you get it hooked up. It needs to know the lb/hr of your injectors and size of engine.

I didn't know if this would be helpful to you guys but maybe just as a reference,,but here's a couple stock 6.1 timing tables.
NOTE: Factory PCM use 2 timing tables, one for Part throttle(14.7 A/F) and 1 for WOT; kPa is Y axis

6.1 09 6Speed WOT Timing

6.1 09 6Speed Part throttle:

New development: AEM finally got back to me!! A little late, since I already pulled the trigger on the MegaSquirt gold box. But their offer gives me pause. They'll give me a ~$460 trade in value on my old AEM/MP Grey box toward an Infinity Series 5 ECU. I could then modify my existing harness terminals to connect to it using their plug/pin connector kit. This is a very attractive option since it frees me from having to take the EFI harness out (and intake manifold) and allows me to recoup some value from the grey box. This means I'll potentially be back on the road sooner and for less $$. The Infinity setup looks very solid and also appears to have a lot of great features w/ custom tune-ability. Then what to do with the MegaSquirt Gold Box?? EFIsource probably won't take it back since they made a custom harness for me (coils under intake). I guess I could use that on a 2005 5.7L hemi that I amazingly just came across for $700 and put it into my lady's 69 Valiant. Though this would be a "low budget" hemi swap using a '73 Duster v8 K-frame and 904. Though that's another story and I'll be picking your brains about it later. What do you think MS or AEM?

Edit: Oh yeah, AEM said they've seen the issue I've had with the MP grey box before, and it's not good. It usually required replacing an eprom chip which they can't source anymore. It's great knowing the problem was "real" and that I wasn't out of my mind chasing down a bad connection somewhere.