I am the newish owner of a 2004 DII (180k) with an Atlantic British replacement engine (about 20k ago). I have been breathing new life in to the truck and have been trying to take good care of it, but am at a point where I can not figure out what the heck the culprit is.

Occasionally, and I mean NOTHING I can reproduce consistently, the first two minutes after I turn the truck on, my RPMs will drop to about 600 and the truck will stumble and make a pretty loud scary pinging noise, almost like there isn't any oil pressure. Tap the gas pedal, and it goes right away. It does this in neutral and in gear. Same fix: raise the RPMs. When I drive down the street, it's completely fine. By the time I get to my first stop sign, about 4 minutes later, the problem is gone for the duration of the voyage.

This weekend, I took about 10 trips to the dump to drop off truckloads of brush so I had time to test a few things. If I shut the engine off, and started it back up after filling up the trunk, the knocking would be there even if the engine was already at operating temp 210F or so on my UltraGauge. If I kept the engine running, no issues at all. However, consistently, if I shut it off, 5 minutes or 2 hours, when I started back up, backed down the hill, and headed off, the drop in RPMs and banging would appear for the first few minutes.

I have plenty of oil in it and have been using 15W/40 Rotella. I even gave in and brought it to the dealer who had their senior tech with 30y of experience spend 3h with it (he LOVED seeing an old Disco) and he couldn't figure it out either.

Is there some electrical circuit that is running that shuts off after the first few minutes and NOT when something reaches a certain temp? Is there a pressure circuit that might be leaking until it really gets up to speed? It's the consistency of time that is making me think it's electrical.

Really running out of ideas on this one. Any ideas on what to test/check next?

Thanks for your help,

Ryan

 

Can you describe or record the "banging".

Do you have a bang or a tick they are vey different noises

Mine scared the hell out of me on day with a loud thumping, turned all the penetrating oil I sprayed on the y pipe nuts on left side some was drawn into exhaust and detonated.

 

SAI valves when open will make it sound like the engine has an exhaust leak or is ticking, but once the SAI solenoid valves shut the problem will go away. Do you hear the blower sound at startup? Usual fault codes are P1412/P1415 if remember correctly for SAI vacuum leaks, broken hose from SAI blower, or an SAI valve which is stuck in the open position.

 

You can disable the SAI by pulling the fuses and relays and disconnecting the vacuum tubing (cap the nipple at the manifold) so you rule that out. Have you checked hte oil pressure? 675 is normal idle speed and cold ish I would expect to see around 20-30 psi and hot around 15-20. Don't think you have an actual engine knock, but low rpm and low oil pressure are not a good mix. BAD maf is usually what causes that stumbling low rpm. Possible cracked flex plate? Low RPM enable engine pulses to resonate sheet metal?

 

Okay, a few things here:

1. Sorry for taking a while to respond to everyone's immediate help. Three kids and a new job.
2. The problem is near impossible to reproduce.
3. The "banging" which used to go away after the first few minutes, came back today after driving around a bit, caused a bunch of error codes, and I managed to
   capture it on video
   .
   1. P0132 O2 sensor circuit high voltage bank 1 sensor 1
   2. P0135 O2 sensor heater circuit bank 1 sensor 1
   3. P0155 O2 sensor heater circuit bank 2 sensor 1
   4. P1300 Misfire detected sufficient to cause catalyst damage
   5. P0305 Cylinder 5 misfire detected
   6. P0301 Cylinder 1 misfire detected
   7. P0303 Cylinder 3 misfire detected
   8. P0171 System too lean bank 1
   9. P1171 O2 sensor system too lean fault banks A & B
   10. P1129 ???
   11. P0300 Random/multiple cylinder misfire detected
   12. P0307 Cylinder 7 misfire detected

Engine was warm and the problem seems to be remedied by increasing the RPMs. If I don't hear the death banging (as in the video) I can still _occasionally_ hear a tap that sounds very similar while the engine is idling. It's nothing consistent and it sounds large and heavy, almost like the flywheel or something big kinda rattling around. It's large enough that I believe I can feel it in the shift lever when it's happening.

Again, the truck has an Atlantic British replacement engine swap done by the PO about 30k ago. The rest of the truck has 188k miles on it, so I am trying to rule out which other bits were transferred from the old engine to the new engine and might be at the end of their life. I plan on keeping the truck for a long time, so I don't mind throwing money at replacing things like sensors or electronics to rule them out and make the truck reliable for years to come. I love it.

Also, I went off-roading with it recently following a HEAVILY modified Tacoma. While I had absolutely no problem keeping up, when I opened up the hood to shoot this video, my PRISTINE engine bay looked like what you see in the video. How on Earth can you keep the engine bay clean if you go through mud or a puddle crossing. I didn't wade at all, but was shocked when I opened up my engine to see this nonsense.

Looking at the error codes, it also seems like 1 coil pack is the culprit. I recently replaced them both and put in new plug and wires. Why only the odd cylinders?

Hmm.

Thanks,

Ryan