Thanks, another new MAF from Amazon on the way, going to try and change out fuel pump today.

 

Pump replaced and no change in behavior: still starts hard, struggles at low rpms and muffled backfiring, requires about 30 seconds of throttle nursing before it settles down and finds idle at 600-700rpm. Drove it several miles today (out of neighborhood) and no issues with hesitating/dying.

It is pretty clear that the muffled in-exhaust manifold backfires (though no misfire codes) is only on one side (driver/left).

As the SAI pump doesn't run when cold starting, I'm going to begin troubleshooting that while I wait for (another) new MAF sensors.

But first I am going to smoke the intake to see if I have any vacuum leaks.

Given the muffled backfires are on one side, I am wondering if: 1) the SAI pump is no running so no positive pressure; 2) the solenoid is opening the SAI valves; and 3) exhaust is flowing back into the SAI plumbing until the solenoid closes. What'ya think?

 

I've never experienced SAI check valve issues, but l've read about them on here...so...could be a possibility if you are getting back-fires or muffled back pressure sounds.

 

Sorry, I missed the muffled backfiring. That is a clear sign you have the spark plug wires mixed up.

 

Except it settles down after fighting it with the throttle for about 30 seconds -- which is how long I recall the SAI pump typically running (before it stopped running).

If wires were switched or bad wouldn't it keep backfiring?

And I replaced the wires and the coil packs (easy job once I moved the coil packs to the front of the engine). Haven't done the plugs (though I have them).

While awaiting a new MAF sensor to replace the other new one currently installed (I still do have the P0102 and P1884 codes -- but no other ones), I am going to smoke test it today.

My "theory" and troubleshooting right now on the SAI is as follows:

1. The pump itself is good (I've removed and tested it);
2. The pump doesn't run when conditions (engine temp below 55C/131F, and above ambient air temp of 8C/46F) indicate that it should;
3. The struggling start issue only occurs when the conditions support the SAI pump running;
4. The struggling start when the conditions support the SAI pump running seems to last for about as long (30-90 seconds) that I recall the pump running;
5. Beyond the 30-90 seconds, if I can keep the engine running thru that period, the engine settle down to a reasonable idle and otherwise runs well for the few mile tests I have taken it on;
6. Once the engine is "warm", it starts up fine, but once it gets cool again, I have the same issue
7. I am guessing that during these cold starts that meet the SAI conditions (engine temp below , the SAI solenoid is opening the valves even though the pump is not running;
8. Given the lack of positive pressure because of a non running SAI pump, exhaust is blowing back into the SAI valves and other plumbing, somehow upsetting the pressure equilibrium expected and causing the whole hard starting with muffled popping thing.

Based on this, I have the following troubleshooting plan:

• Disconnect the SAI solenoid and see how it starts up;
• Reconnect the SAI solenoid, the jumper the SAI pump to run continuously (it could not find any reference to the SAI relay in either the RAV or Owners Manual but was told that it is the #6 relay in the engine compartment fuse box, same socket where the glow plug relay for a diesel would be -- can anyone confirm this, otherwise I am going to have to do some continuity testing first?) and see how it runs

How's that sound for an SAI troubleshooting plan?

Finally, the new fuel pump running sounds loud to me. It sounds a bit loud to me. Unfortunately, I never checked the sound of the old fuel pump before pulling it (and it was a super PITA for one person to both push the new pump down against the springs and get the retainer ring started, so no going to swap them in and out again). I would post a mp4 video but apparently that is not an acceptable file format here.

 

I would do the plugs and confirm wires. I don't think I've ever replaced coils and wires and not done plugs just doesn't make sense to leave them out if chasing an issue.

edit: I don't have SAI in either of my trucks so no help there unfortunately.

 

Your SAI test plan sounds fine.

Backfiring in the intake is a sign the spark is being ignited while the intake valve is open (much too early). Backfiring in to the exhaust is a sign the spark is not being ignited until the exhaust is opening (much too late).

The main difference when a Disco starts is it runs a bit richer. You can disconnect the SAI solenoid andor the vacuum source and the manifold valves should be shut. Easy way to test the manifold vavles is to disconnect the vacuum line and the pump line and see if you hear exhaust on startup, if you do the valve is bad.

 

As I have now disconnected the solenoid and it had not effect, I next want to try and run the pump by jumpering the relay -- once I know the which relay it is. Is it #6 in the engine compartment fuse box?

Next step will then be to move on to the SAI valve itself, starting with the one on the driver side as that appears to be where all the muffled exhaust "back pressure" thumping appears to be coming from.

And since it was warm today, tried running the AC and nothing. Clutch is not engaging. Jumpered that relay socket and still got nothing, so either the wiring or clutch itself.

 

Unless I missed it for your high revs, try cleaning out your IAC valve with some type of carb/brake cleaner and a tooth brush.
I do this every oil change to include cleaning the throttle body & plate, cleaning the MAF sensor along with greasing both driveshafts.

 

I swapped out IAC valve earlier with another known good (I think) used IAC, but I will clean it out tomorrow anyhow as it's an easy do.

I like the easy test to see if the SAI valves are good: disconnect the vacuum and the air pump intake, start 'er up and see if any exhaust is leaking out of the valve.

Doing that tomorrow as well as jumpering the SAI pump and see if I can get it to run (I pulled it and put 12V on it and it ran).

And going to smoke test my intake for any vacuum leaks.

And renew the plugs.

Also discovered today that it appears my ac compressor clutch isn't energizing.

Land Rovers always keep you busy!