1989 Crown Air Flow Meter issue?

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361UZ

Member
Messages
140
Location
Canberra ACT
HI guys. Hope all is getting better in whatever neck of the woods you are from!
My 1UZ (powering the Chev hot rod) has developed a problem. I am completing the wiring, using the Crown loom and eliminating parts I dont need. But the engine, ECU, ECT etc wiring is absolutely stock. I work on the wiring, then do a test start/run to make sure everything is still ok. But recently over the last few starts, the engine progressively idles worse and worse. Ok when cold started, but as the temperature rises, the idle drops and eventually stalls. Now: it is ok cold, then begins to "lope". The revs drop from about 1000, to almost stalling, then it corrects, then drops again, but it is also very rough, like its running rich.
If I rev it up to about 1500 to 2000RPM, it is very smooth.
This issue has been getting progressively worse over the last few starts and I have made no wiring changes in this time. Yesterday it wouldn't idle at all (temperature about 1/2 way between cold and normal). It also threw a code! I cannot find the diag codes for a Crown anywahere. I have a set from an LS400 (1990). The code I am getting is 31 which on the LS400 is Air Flow Meter. (Makes sense given the conditions I am getting the problem under).
I have checked the wiring (all bog standard) from the AFM to the ECU. Agrees with the wring diagrams. I am seeing +5Volts on the AFM. At the ECU end I see +5Volts going to the AFM, +3 Volts on the inlet air temp wire (very cold day), +5Volts on the AFM output (car not running, just IGN on).
Questions: If I scope the AFM output to the ECU, what should I expect? Is it a waveform or a voltage level?
I have checked for corroded pins etc, removed and checked the AFM etc, all looks like new. The ECU pins are all good and bright brass coloured. Checked inside the ECU, no swollen/leaky caps. Well, very few caps in there at all. None around where the AFM wiring plugs in.
If I clear the code, it will re-occur at next start. Although the problem has been around for a while, the error code only happened yesterday, but now is solid. If I clear it, it will re-occur again straght away at the next start.
Summary: Am I interpretting the error code correctly (Is 31 a bad AFM on a 1989 Crown)? Anything else to check?
Thanks heaps!
 

361UZ

Member
Messages
140
Location
Canberra ACT
Ok...
Progress. I bench tested the AFM and it appears to work. Using a 5Volt supply connected to the +5Volt wire and the two grounds to the negative, and using a pull-up resistor (10K) as a substitute ECU.
Using a 12Volt computer PSU fan, and monitoring the AFM output on the CRO. As I increased the airflow (by screwing the fan power supply from 12 volts to about 30), I had a square wave output at about 25 fan Volts. Unfortunately I ran out of time. Didn't check if varying the air speed varied the square wave frequency. Also didn't check the inlet air temp lead, but I think that's working (shows about 3V when connected to the ECU).
Of course, I should have just disconnected the AFM when the engine was running to force it to use its default maps.....
AFM output May20.jpgAFM output May20.jpg
 

361UZ

Member
Messages
140
Location
Canberra ACT
Thanks Kelvin. Yes, the "plumbing" for the IAC is as standard, although I have removed the resonator (the black plastic box) from the inlet path, so its the air cleaner, AFM, right-angle rubber hose, then to the throttle body (as yet unmodified). This is how I have had it since I removed the engine from the original 1/2 cut, and it ran 100% ok after I removed it.
I also used a more powerful fan and, yes, the frequency increases with fan speed (as expectd) and the inlet air temperature sensor works ok, as in the volts decrease from about 2.4volts at 15 degrees to about 1.7Volts at 40 degrees. That's with a 6.8K pullup resistor. Not sure what the ECU uses.
Tomorrow (If I get time) I will put the AFM back on and start the car. If it still has issues, now I know what I am looking for, I can scope the AFM output at the ECU end, If the engine still runs bad, I will try disconnecting the AFM.
Jeff
 

361UZ

Member
Messages
140
Location
Canberra ACT
OK, for those watching (thanks).
As above, AFM re-installed. Engine started (neighbours not home!)
Ran ok cold. As it warmed up it began to die. Got to the point where it dies (to zero revs on the tacho) then kicks into life, dies, etc.
Revved it to about 1500 - 2000 rpm (digital tach so a bit low on resolution) where it runs smooth.
Checked AFM output at ECU end. +5V up until about 1500 - 2000 rpm, where I get the square wave as above (hence it runs smoothly).
So, why no waveform below 1500 rpm?? I verified there was no other air-path other than through the AFM. Put my hand over the AFM input. Not much airflow but it did stall. (I could feel lots of suction)
I disconnected the AFM and the engine ran really well. Smooth consistent idle down to about 900 rpm.
So I then disconnected the AFM wire from the ECU, used a pullup resistor to simulate the ECU logic, and confirmed all of the above was exactly the same. Pointing to a dud AFM in my view (of course, error codes 31 as well). Interesingly, it ran like a dog at this stage, with only the AFM output wire disconnected, so presumably the ECU didn't know the AFM was disconnected, so couldn't use its default maps??
In amoungst this the fuel pump "died". The engine was running badly, so I checked the fuel return to the tank - nothing. Not a drop? With the engine not running there is plenty. I bypassed the Crown fuel relay (direct to the battery) and there's plenty of fuel in the return line (with the engine running). Another bit of research required!!
Unfortunately after this I tried it all again, and although it idles beautifully, it wont rev - at all. At about 1100 rpm, the engine dies....
It was getting cold (car is outside) and dark, so I gave it away.
But I need an AFM... I notice that the part used on my Crown is also used on quite a few other Toyotas, so off to ebay (unless some helpful forum member can help?)

Thanks for reading.
 

361UZ

Member
Messages
140
Location
Canberra ACT
Update for anyone watching......
AFM's (Part number 22204 - 42010 as used in my Crown) although used on quite a few Toyotas, seem to be scarce? There ARE new one available from China, but do they work?
Part number 22204 - 42011 comes up sometimes as an alternate, byt the construction of that is different, in that it has two wires with a sensor of some sort mounted between them, more like the AFM on my Commodore. Apart from that the construction appears the same. Anyone had definitive experience with using that AFM on an early Crown ECU?
 

361UZ

Member
Messages
140
Location
Canberra ACT
Hi Rod.
As near as I can determine (so far) the 22204-42010 was used on 91 - 95 LS400, sc300 and sc400. Also 86 - 92 Supra Turbo (7mgTe).
Some people say the 22204-42010 is for the turbo Supra, the 22204-42011 is for the NA version.
There's a lot of conflicting info re the 22204-42011 being a replacement for the other part number. Kelvin said the 22204-42011 is a later version of the same part, (ansd I beleive him), but they are different (as in my post above). Maybe the extra sensor is used on later models, but it simply ignored on the earlier cars?
I would like to sort this out because some ebay sellers will send you a 22204-42011 even though you ask for the other one. And given how flakey the Fuji units seem to be anyway, you wouldn't know if you got a dud 2nd hand one or they just aren't compatable. Even so, how do you know the AFM is reading spot on so you get the correct air/fuel ratio?
 

361UZ

Member
Messages
140
Location
Canberra ACT
So... Bought a new AFM. None of the correct models available in Australia or New Zealand. Next best option is to buy one from China (yes, I know). For the interested, it is part number 22204-42011 - well so the box says, there being no part number on the unit (surprise, surprise). I specifically asked "Jason" the sales rep, if the part he would send me IS 22204-42010 (ie a Crown karman=vortex unit). I sent him pictures, clearly showing the part number. He sent me pictures of the unit he said he would send me (which clearly show the correct part and part number).. Nup;... He sent the wrong part. Paypal dispute pending. Lota of bad reviews will ensue!

Anyway, new AFM installed... Engine started (cold) ok. very rough. idled ok when cold. As it warmed up the idle started to die away. Check engine light. Error 24 and 31. Did I expect anything less? Once it warmed up, it wouldn't rev above 1500 rpm at all. It cut out completely.

Some pictures: Original on the left, new one on the right:
AFM1 Original on left New on right.jpg
Left is original, karman-vortex AFM. See, no external components. Right is new "hot wire" type (I assume). External components. Look like the thermisters used on most common AFM's, eg Commodore.
While waiting for the new AFM to arrive, I dismantled the old one, Cut around the potting and removed the back cover. The electronics are potted, ie covered in a protective layer etc. Its fairly simple inside. You can clearly see the pcb, the LED/sensor assembly, Should be an easy fix. I was going to remove the bits to see what was wrong with it, but didn't get time.
After testing the new one (see text above), I re-installed the old one. Started the car. Idled well. revved it, and it revved very cleanly. Back down to idle ok... "This is mad" I thought. It cant be ok... Get the scope out, set it up, and sure enough. A square wave at idle, and right up to 4500RPM. The old one is working! And the engine revs up very quickly! It used to be very sluggish with lots a black smoke. Now it revs up instantly, and no smoke. Even snapping the throttle open - it just revs straight up.

Now to continue with the bloody wiring!
 
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