I have an '04 D2 HSE with SAI that had been getting progressively finicky until it finally died on the road and had to be towed home.

Progression of failure was that it would lose power/ not rev above 2,000-2,500rpm, would limp home and sometimes die, but after a while would restart and run OK for a while.

It started with only a 0102(?) MAF sensor code and a right and left O2 sensor codes (which I am pretty sure were related to/caused by the MAF code), replaced the MAF with a new Bosch.

SAI has also not been running as best I can tell and threw a bunch of codes when I jumpered power to the wrong blade on the SAI a relay socket and generated like 18 short circuit fault codes, so thought I had fried the ECM. But this was apparently fixed by replacing a blown #2 engine compartment fuse (whew).

Given how it had behaved prior to completely giving up, I assumed it must be a fuel delivery issue (it "felt" like fuel pump failures I've had in the past on other vehicles) and was getting ready to replace it, but I got a pressure gauge on the fuel rail schraeder valve and it read 50psi plus when cranking and held 48psi for 10-15 min thereafter. (spec is 55psi, albeit this was with a Harbor freight pressure test gauge so I am sure it could be plus or minus 10 percent).

I know the 3 rules of engine troubleshooting: compression, fuel, spark.

I don't see the failure mode relating to fuel, so going now with spark.

How would the smart guys out there approach this?

 

You can check for spark if you have a timing gun sitting around. Just clamp to each lead to see if its firing. Otherwise, I use an inline spark tester light to ensure that i'm getting good spark when diagnosing. I'm sure you can also look through the ECM for that into as well. That's how I diagnose a coil on plug type setup like on my other cars.

 

The progressive failing mode doesn't seem to point to anything like injectors or air intake -- I guess it could be a TPS? Any way to test the TPS?

Next would be the coil packs? Test each plug wire to see if it is producing spark?

What after that?

The the rules of troubleshooting may be a little dated, as I guess it could be a CPS or CMS as well?

 

andino, would a failing coil pack exhibit the progressive failure mode I described?

 

Its possible that a failing coil could but I'm not 100% sure on that. I know when mine started to give up the ghost, I just had a huge loss in power along with a flashing check engine light. CPS would be a lot more binary if that was going. Either the truck would start or it wouldn't (typically when hot).

I would try to rule out that your coils are faulty by checking spark first. The job to get to the coil packs is a decent effort if you have SAI. Its easier if you don't have SAI but still a PITA.

 

Have you ever replaced the CPS? When they get hot they will cause stalling or no start when warm. DO NOT use anything but a Bosch CPS. MAF wise the truck will actually run without it plugged in. It'll stall at first, but eventually it'll keep going when the ECU goes to a default value.

 

To complete eliminating fuel delivery, if I have 50psi on the injector rail, then I don't have any kind of venting issue that would be creating a vacuum/suction in the tanks?

The injectors are directly controlled by the ECM, and unlikely that's failed all at once, right?

I'll test the coils for spark today when I get my inline tester back from a friend. Replacing the coil packs will not be a big deal as I relocated my coils to the front of the engine years ago. Could the coils fail slowly rather than all at once?

No, I have never replaced the CPS. It's the original with 190K on it. Could it fail gracefully, i.e., slowly?

The RAV is pretty clear that the engine will not run with a bad CPS. It implies that one test for a failed CPS is that the tach doesn't register RPM. I'll check that today.

It also says that when the CPS is replaced it needs to be calibrated with a Testbook (some kind of factory tech tool). Is this really the case or will it self-calibrate? (On other vehicles, I've replaced the CPS with no need to reprogram anything.)

It doesn't say the same about the CMP, i.e., the engine won't run without it, so assuming a failed CMP would still allow the run?

And compared to the CPS, the CMP looks like a PITA to replace. Do you need to remove the crank pulley to get at it?

From the RAV, it says the ECM use the following inputs:The ECM processes sensor information from the following input sources:

Ignition switch (position II): if the fuel rail has pressure and the starter motor cranks, then not an issue here, right?

Crankshaft speed and position sensor: will check the tach.

Camshaft position sensor: not sure how to test

Engine coolant temperature sensor: wouldn't effect running?

Mass air flow sensor: not mandatory to run?

Intake air temperature sensor.: this is integrated into the MAF sensor, so if you can disconnect the MAF and still run, then this isn't mandatory

lKnock sensor: not essential to run

Throttle position sensor: needed to run?

Heated oxygen sensors. not needed to run

High/ Low ratio switch: not needed to run

Fuel tank pressure sensor (where fitted): does my NAS 4.6L SAI have this feature? Is it needed?

Thermostat monitoring sensor (where fitted): does my NAS 4.6L SAI have this feature? Is it needed?

 

When a CPS starts to fail = when it gets warm & the vehicle will usually stall out and not restart until it's cooled down. I've never had one just completely die they just go intermittent and cause ya hell. Replacement is just swap it out no calibration needed.

 

Thanks, didn't know why it would need calibrated (never had to do it on any other vehicle), but the RAV says it so it must be right (hah).

I did the tachometer diagnostic "test". When cranking for first 1-3 seconds, no activity from the tach, then when the engine seems to want to fire, the tach "jumps" momentarily then settles back down to zero while still cranking. Does this point to the CPS -- or the coils?

Also, in the spirit of full disclosure on the coil packs, it has what I believe are the original Bosch coil packs on it (currently 190K miles, my son was given the beast at 128K with full maintenance records -- and I mean full, the previous owner never did anything on their own -- and there's nothing about coil packs in those records). I bought some knock-off coil packs when my son and I did the rebuild (after all, how hard could it be to knock off 100 year-old technology, Forrest), but they threw misfire codes only a few months after the rebuild. I bought a coil relocation kit to get the coils out from that SAI plumbing complicated sweatbox space behind the motor and then put the original coil packs back on the relocation platform at the front of the engine. That was 5 or 6 years ago.

 

Start with a replacement CPS. If it's original 190k = lived a good life. Coil wise you'd have a ton of P0300/P0301-308 faults. CPS when it acts up sometimes won't ever toss a fault code. In all my years I've only had one generic CPS (Not Bosch) throw a CPS fault. Sensor worked but engine stumbled and threw a few misfire faults. Viewed the faults saw the 1 CPS fault replaced it with a Bosch unit and 4+ years now with zero issues. I've also seen CPS sensors get bent from cracked/broken flex plates and cause all sorts of grief as well.