Need help tracking intermittent problem with 6.0

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workingdog

workingdog

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I recently took delivery (after 2 years at 3 different shops) of a 6.0 conversion on my '66 FJ40. The 6.0 sits in front of an NV4500 and the stock transfer case. The 6.0 is approximate 2003. I need to figure out the exact year for sure.

When it runs, it runs great, but it has an intermittent issue where it feels like it's dropping into limp mode. Some times it does it all the time, but I just drove it back from a shop to look at it and it didn't do it for them and it didn't do it for me all the way home. It seems to lose power and won't respond to the throttle. It's not dying, just sounds funny and barely able to make headway. Feels like limp mode, but I don't want to jump to any conclusions.

So, my question is, how do I track this down? What kind of device can I get to plug into the OBD II port so that next time it happens, I can then see what's going on?

I have to say, I highly recommend a 6.0 in an FJ40 - when it's working, it's really fun.

Peter
 
What ECU are you using?
 
shawnfj40 said:
Did you have a lot of trouble getting a Ford Diesel in a 40? I thought the 6.0 had a lot of issues?
Click to expand...

I believe he's running a GM 6.0 gas engine.
 
2x What ECU are you running?
What harness? Is the harness original to the engine and ECU?
Did the 6.0 originally have a manual transmission behind it?
 
Attached ECM sticker.

This is a 6.0 GAS vortec (told it was 2003, but I haven't confirmed). Got it from a guy that had hot rod plans that he had changed, so I don't know what it was in front of originally.

IMG_2534.webp
 
What I could find online says

Delphi ECM
Came from: 2000 GMC 3500 6.0L Auto
SERV.NO. 12200411
HDW NO. 09386530
12201281
DFNN

And then somewhere else online I found this

'06 GMC 3500 1 ton dually

I'll get the numbers off the engine and see what they say.
 
I would start with an ECM that you know matches the year of the motor. OR, I would send it out and have it reprogrammed to match your motor and have them delete everything except the sensors necessary to run the engine. If you don't have ALL of the sensors hooked up the ECM will be looking for a signal. If it's not matched to the motor in may be looking a specific voltage or range it's not programmed for. If you have a frankenharness you may also problems there, too.
 
Harness is from Howell, and in theory, the ECM was totally cleaned up when the final step of the conversion was done.
 
I guess what I said above about reading potential fault codes was wasted text?
If you have an OBDII port just do it and check for codes you have nothing to lose!
 
Run the codes, that a shop didn't check the memory is beyond puzzling (meaning, find another shop). I've had a similar issue and it was either the TB or the DBW pedal (throttle body, drive-by-wire). Everyone says replace them at the same time - and that cured it.

That said, I need a lot more information. Is it DBW? (they changed from throttle cable to DBW in roughly 2003 - thus a 2006 computer on an older motor leaves me puzzled) are any mods done to the motor? how did you handle the fuel system? Who programmed it - I have a love/hate relationship with Howells so any claims by them I'd warn you to double check. Intermittent problems tend to be electrical.... and way too often, grounds.
 
Same issue happen to me on a 5.3 a few years back. Drove me nuts for months and found out after a Dyno test that I had a bad ground on the stand alone harness by one of the O2 sensors.
I used the oem harness and it was sent out for modifications. I sent it back for the second time, but they never fixed it.....took it apart myself and found the issue.
I am not saying it could be the harness, but again, same scenario affected the performance of my two front oxygen sensors creating exactly what you are describing.
Another thing I did after that was moving the fitting directly into the header and swapped the sensors to AC delco instead of Bosch.
Edelbrock used to make a beautiful header specifically for LSx swaps with the bung already welded into it. Not sure what's out there today a days...
 
There were no codes thrown. I've cleared and the next time it happens I'll check write away. I have my ODB ii gauge in there, so it's easy to check.

It's drive by cable. So the sensor on the throttle body is a possibility - as is a bad ground somewhere.

Peter
 
One of the reasons I don't like Howells is the connections in the harness for my TBI system were utter crap. No heat shrink, lots of electrical tape, and terrible solder joints. I went through 3 ignition modules before I found a solder joint where they didn't cut the sharps off - it was grounding through the harness.

If it isn't the TP sensor or a bad ground, I'd start pulling wire covering and checking connections. I hope it isn't and mine was a Friday harness....
 
So, my original question still stands. What can I plug into the ODB ii that will record the ECM so that when it happens again, in addition to seeing if there's a code, I can check what, if anything, happened in the engine parameters. Do I need an HP Live box?
 
Managed to take it for a run this morning. No codes when I left. It had thrown P0507 when I got back. Idle RPM higher than expected. I think that has more to do with the lack of VSS. The shops turned up the RPM to keep it from stalling when coming to a stop. I need to figure out how to rig a VSS into this. It did the behavior once, but no other codes were thrown. Will going into limp mode throw a code?
 
Recording is different then reading - recording needs something like HP Live. That said, I've heard tell that Android and Apple both have OBD2 recording available...

That code can be thrown by a TPS, vacuum leaks, or wiring connections to the throttle position sensor (TPS). VSS are available and pretty common... they go in-line with your speedometer cable and provide either an output for solely the VSS or for a cable and VSS. I'll go look, I may have one in the box-of-parts I got from Dakota Digital - I used solely electronic and they sent parts to keep the cable-out for the stock gauges.... if not, they're a good source for the part.
 
from looking around, the set of sensors available to monitor via ODB ii seems pretty limited. I have an ODBLink dongle and I'm waiting for an android phone (the wifi connection available for iOS is not reliable). I'll see what I can record with it. My Scan Gauge shows the TPS wandering around. I assume it's trying to tell me the position of the gas pedal when it's DBC. But I should be able to get it to show me the position of the throttle plate in the throttle body - but I don't know how.
 
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