1UZ-FE problems in a Cobra.

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Schnitzel26

New Member
Messages
10
Hi all and thanks for letting me join. A mechanic friend of mine has asked me to look at a Cobra replica that has had this motor installed, complete with supercharger. I am an electronics tech. The owner of the car was driving it regularly until one day he stopped for lunch, the car had been fine for ages, but when he went to go home, it wouldn't rev, kept stalling and cutting out. The mechanic says that he has either replaced or had checked ALL sensors etc. The ed engine light and OBD port aren't connected/working. All leads, plugs, coils, distributor caps and ignition modules have been replaced. The ECU has had the caps replaced and supposedly been tested. I just don't know where else to look. Does anyone have any ideas? The owner hasn't put fuel in it and the fuel pump seems to be delivering heaps. It starts, idles, and when you rev it, it dies and usually stalls. Cheers and thanks in advance.
 

361UZ

Member
Messages
158
Location
Canberra ACT
As an electronics tech you would know to diagnose a problem you need info.
What model engine? What was it out of? What sensors etc have been retained? Manual or auto? Factory ECU? Any tuning changes? If not standard ECU, what does it have?
I assume its not the standard ECU or the OBDII and check engine light would be connected.
You really need the diagnostic stuff to be connected and working to pinpoint any issues.
 

Schnitzel26

New Member
Messages
10
Hi 361UZ. Thanks for the reply. I've just noticed that I didn't put the engine model in, old age creeping in. It is a 1UZFE with supercharger that has been put into a cobra replica with a five speed manual box behind it. Unfortunately information is pretty light on, as neither the owner or mechanic know much about it. I have had the ECU out and it has the following numbers on it - 89661-30430, Serial No 17500024D3M. One of the multi-pin connectors is not connected to anything, and the mechanic tells me this plug is for all the auto transmission control etc. He claims to have either replaced or had ALL sensors tested, including the ECU. There is no engine check light as the dash is just a few small coloured 12 volt lights, so basically a real mess. He has had two auto electricians look at it, and one used a BNC connector (unbelievable) to connect the O2 sensor, and the other completely stuffed the ignition lead firing order. This all happened after the ECU was tested, so I don't know if it has been damaged. I changed all the caps - no different. I have checked all the wiring and voltages and they all appear to be normal. I really can't tell you much more, but I am still leaning toward the ECU. The weird part is that it gets driven regularly, didn't play up until they went for lunch and when they came out it had the problem after about two minutes. The fuel hadn't been re-filled and nothing obviously was done to the car whilst they were at lunch. The owner is hopeless and I can't even tell you what the engine came out of, except that he bought the car as it is.
 

ivan129

BlownZX
Messages
152
Location
Some where
Have you checked the basic mechanical and electricals of the engine? Ignition timing correct? compression ok on all cyls? cam timing? maybe the cam belt has skipped a tooth or 2. You can often pick this with a comp test. Color of plugs consistant and ok? Firing order correct? coil lead not broken, coil leads connections not corroded, coils not breaking down. No vac leaks?
 

Schnitzel26

New Member
Messages
10
I'll need to check with the mechanic as to whether or not he has checked the timing etc. I have replaced all the leads, both distributor caps, both coils, new plugs, firing order fine, no air or vacuum leaks that I can find. He had bought all these parts along with quite a few new sensors as no-one seems to be able to locate the problem. As I said, it ran fine one minute, then it started playing up. It was all very sudden.
 

361UZ

Member
Messages
158
Location
Canberra ACT
I hesitate to say this, but have you or can you check the AFM? My Crown 1UZ has the original AFM - a Karman-votex unit. It failed one day. The symptoms were similar to your's at one stage. It would idel ok, then if I cracked open the throttle, the engine would stall. No amount of gradual opening would get it to rev. I broke out the 'scope and checked to output (after making sure the AFM had +12V and ground). The scopr revealed no output up until aboout 2000RPM (IF I could get it that high). Normally the AFM puts out a square wave, 0volts to +5. Assuming your problem MAY be AFM, try disconnecting it. The ECU should default to default mapping and run sort of ok. Yes, you will get a check code and that leads me to another possibility.
What if you have an error that's causing the engine to go into limp home? Have you tried resetting the ECU. I know you are travelling blind with no check light, but..
On that, since you have the ECU details, google them. That will help, and you can find out which pin the check lighht is connected to. Then you can get any codes.
 

Schnitzel26

New Member
Messages
10
Thanks again. I also suspected the AFM, and I asked Wayne (the mechanic) and he said it had been tested, but it has a small crack in the top which I don't like. The voltages are there, but the manual I downloaded shows the AFM as having three wires, and the one fitted to the car has five. I did manage to find a schematic for the ECU, but your suggestion is better in that the manual might apply to a different model. According to the manual I downloaded, the two major factors for this type of problem are the MAFS and the ECU. Everything else seems to check as it should, but yes, without the proper warning lights and inability to use a scan tool, it makes it very hard. I'll let you know how I go, I'll drag the scope out and have a look at the waveform during the week. I have tried the ECU reset. Your issues when your MAFS failed sounds very much like ours. Thanks so much.
 

361UZ

Member
Messages
158
Location
Canberra ACT
Yeah, this is the problem when people just build and don't leave tracks! The part number of the one I have is 22204-42010. The part number is easily visible just looking at it. I dont suggest at this stage buying a new one.
.
It has 5 wires, because 2 are used for the inlet air temp sensor. Mine is a karman-vortex unit (very early) but later ones are hot wire type. I dont know what waveforms etc to expect on those types. Mine is mounted on top of the cast alloy AFM assembly, by small screws. Very simple to check.
See how you go
 

Schnitzel26

New Member
Messages
10
Thanks Gloverman, you would think so, wouldn't you? I have spent a whole day rewiring some very dodgy joins. I'm hoping today to wire in the MIL and the diagnostic port myself, but because this is a conversion into a kit car, everything is all over the shop and very hard to get at. I'll keep everyone that has been so kind to offer advice on my progress. Cheers.
 

361UZ

Member
Messages
158
Location
Canberra ACT
You beat me to it... See my suggestion above.
I checked your ECU part number against the one am using in my Chev. Same part number, serial number on mine is 175000 - 2403. But I still wouldn't be blaming the AFM without evidence. Did you manage to read the AFM part number?
Do you have the ECU pinouts? The diagrams are all over the web. Google the part number. In the diags you will find the wiring to the engine check light. Wire it up. And while you are at it, wire up the diagnostic check connector. Then you can see the error codes.
Fun times, I hope your friend is appreciative!
 

Schnitzel26

New Member
Messages
10
I have found a little more info. The motor is out of a 1990 Crown apparently, and I have a print-out of the ECU connections. The engine check lamp output is not connected and appears this is meant to be. Most of the plugs on the 22 pin connector are either cut off or not used. The ECU has been wired up to what was a Torana dashboard and it uses a Torana fuel pump, so the fuel pump sensors etc are also useless. I found a small crack in the MAFS and taped over it, and it ran like a Swiss watch for ages, until I put it into gear, reversed about 10 feet, drove forward about the same distance, and as soon as I did that it started missing and cutting out again, and now the fault is back. When cold and just sitting there, it runs fine until you try and drive it. It's driving us nuts.
 

Schnitzel26

New Member
Messages
10
Would anyone know how reliable these ECU's are? Also, are they prone to sudden failure as in this case, and would it be possible to replace it with a known good one. I am told that the foreign ECU's that are available are differently wired, and the connectors don't fit. Everything seems to be pointing now to a faulty ECU. P.S. I tested the MAFS as per the manual and it tested fine.
 

361UZ

Member
Messages
158
Location
Canberra ACT
As to reliability, I can't say. Mine works. That's the only one I have had experience with. Torana dashboard, as in Aussie Torana? Cant see why that would be an issue, except it uses a Torana fuel pump? Torries had carby's. Fuel pump pressure 4 or 5 pounds. 1UZ are fuel injected. 40 50 PSI. Unless maybe the Torrie pump is being used as a lift pump, and there's a high pressure pump in a surge tank somewhere?
Where is the crack in the AFM? If it lets air into the chamber where the karman-vortex sensor is, it could cause issues. And (dont take this the wrong way, I am genuinely interested for my own sake) how did you test the AFM? I had similar issues and mine just came good, so it would be nice to have a quick test to verify it's operation.
One more question: do you mind me asking where you are?
 

Schnitzel26

New Member
Messages
10
As to reliability, I can't say. Mine works. That's the only one I have had experience with. Torana dashboard, as in Aussie Torana? Cant see why that would be an issue, except it uses a Torana fuel pump? Torries had carby's. Fuel pump pressure 4 or 5 pounds. 1UZ are fuel injected. 40 50 PSI. Unless maybe the Torrie pump is being used as a lift pump, and there's a high pressure pump in a surge tank somewhere?
Where is the crack in the AFM? If it lets air into the chamber where the karman-vortex sensor is, it could cause issues. And (dont take this the wrong way, I am genuinely interested for my own sake) how did you test the AFM? I had similar issues and mine just came good, so it would be nice to have a quick test to verify it's operation.
One more question: do you mind me asking where you are?
I used a service manual I downloaded, but the pin-outs on the ECU are slightly different. There is a static test of resistance you can do for the AFM as well as a voltage test using an oscilloscope, which I have also tried and it appears fine. I have attached the relevant pages. I am in Tasmania in Australia.
 

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361UZ

Member
Messages
158
Location
Canberra ACT
I used a service manual I downloaded, but the pin-outs on the ECU are slightly different. There is a static test of resistance you can do for the AFM as well as a voltage test using an oscilloscope, which I have also tried and it appears fine. I have attached the relevant pages. I am in Tasmania in Australia.
Thanks mate! I haven't got those. The diagram in page 3 confirms that the AFM is a karman-vortex unit. The resistor is an LDR. The led is infra red. It shines on a mirror and the LDR picks up the reflections. The mirror is mounted on a flexible mount that is caused to oscillate by ultra-sonic waves, which are caused by a vortex created as air swirls around a triangular shaped air "splitter". The more air flows in, the higher the frequency of the ultra-sonic waves.
If your's is testing as per the manual, it looks ok to me!
 
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