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The mkiv Supra Owners Club

HAC Sensor Circuit


Markie

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Anyone on here I can take the car to?

 

Just spoke to Toyota and they said there is no guarantee they will find the problem in the given hour so it could take them a few hours @80 +VAT each hour..! They also said they only have the data for the UK cars, so its sounds like it could just be pot luck?

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UPDATE:

 

Had the ECU tested and it was found it was faulty.. Turbo pressure sensor circuit.. Cost me £300 for diag, parts and fixing, Auto Tek in Dorset was the company.. Sounded like they knew what they were doing..

 

Anyways, ECU back today.. Still the problem remains :-( however on getting back to the house I found no error codes logged, so no idea what's up.. Starting to think again is it that fuel additive again but thought that would be rough at idle and low speed as well, or maybe it's shifted some dirt into fuel filter to something..

 

Grasping at straws now, and it seems the ECU did have an issue and error code 35 was being logged before getting the ECU looked at.

 

I did the test run earlier without the FCD connected so then I thought is it fuel cutting, but it's more of a stutter and I was not boosting over 1 bar.

 

Any ideas? Starting to think I may just sell up now, don't have the time for this anymore :-(

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Update.. Had a Turbo pressure sensor from Brad. Try it this morning, still the same..

 

I have not reset the ECU yet, but I don't think it's gonna matter. But I will and see if I still get the Error Code 35

 

What I did do though from reading another Supra forum is test the voltage to the sensor which is meant to be about 4-5v and mine is showing 4.8-5 so does this mean the wires and ECU are fine?

 

It is starting to look like a Toyota diag now :(

 

Don't know if it's me, but the engine temp does not seem to reach it's usual temp, it seems to run a bit cooler going off the gauge.

Car still idles fine and seems ok at normal running. When Turbos seem to get more involved though it does start playing up again.

 

Would O2 sensor gone cause it? I did not think so as it was an instant problem from all fine and we'll and the next second, problems and very noticeable problems. Not like a more subtle misfire/splutter I have had before when O2 sensor needed changing,

 

 

It's plausible that; without resetting the ECU, the sensor changing exercise has proved nothing.

 

I'd swap that MAP sensor again and reset the ECU, to then see what it's like before digging deeper.

 

Low engine temp could be a faulty thermostat which could increase fuelling.

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Hi Dave..

 

Not sure what you mean.. I have changed the sensor and the ECU has been out of the car for 3weeks so would of thought that would of reset it.

 

The voltages from the sensor before I sent the ECU away seemed to be looking normal from my basic testing..

 

I have noticed the engine temp lower than usual but put that down to short test run and there being an error code before.

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If you've reset the ECU and ran it for a while then excuse me, I missed that. :blush:

 

 

Closely inspect the 3 wires to the MAP sensor socket and/or depin clean and tease the contacts up.

 

If that doesn't do it try test swapping the ECU.

 

 

Do you have an aftermarket device wired to the MAP signal?

Edited by David P (see edit history)
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Could not see much wrong with the wires to the sensor. The reading to the sensor was about 4.5-5, as I think it should be.

 

I have got a HKS FCD in between the ECU and the Sensor reading wire.. However I did bypass that on my test this afternoon..

 

I would love to try an ECU but a manual VVTi one is hard to find. I have had the ECU tested and fixed though.. Or so they said. Not getting any error codes anymore..

 

Well saying no error codes, just getting a constant flash of the engine management light when doing the E1 TC pin trick.. It was giving me error 35 before..

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You mean the connector plugs that go into the ECU?

 

I just thought with the error code and now the ECU having been repaired and the error code stopped that the darn thing should start working..

 

If it was a connector fault they would not of found anything wrong with the ECU? I will give it a visual check though..

 

Any idea who I can take it to now though who would be able to troubleshoot better than me?

 

Dave the FCD currently is not in the circuit, I have put the Turbo pressure sensor to bypass that at the moment..

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Hi Dave.. Yeah bang on.. signal wire from MAP sensor now back connected and bypassing the FCD.

 

I did have as normal readings as possible from the sensor when I tried without obviously having some equipment that I could connect to intake plenium to provide the pressure instead of me trying to read the boost off the gauge and also check the voltages outputted.

 

This was before the ECU was sent off, so thats why I was pinning my hopes to the ECU being the issue as the sensor readings seemed ok.

 

- - - Updated - - -

 

I meant the wiring in the engine bay. Ecu connectors should be mint unless attacked in Japan before import.

 

You could try Steve at Silverline Racing (Which basically means I will probably end up fixing it for you;)).

 

Lyndon.

 

Haha.. Tidy, if its no go this weekend I will give him a ring butt.. Cheers.

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Just had a longer run.. I don't think it matters if it's under load.. Seems to happen on straight as well, but it only seems to start the stuttering at approx 45-50 MPH, don't know if that helps diagnose..

 

Temp is a little low, but maybe it's now the cold weather and not able to work the engine, so I think that is normal.

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I'll take a look at codes tomorrow morning.. Not stripped plug yet, was dark when I goy home :-(

 

Did not look at revs.. It's deformed not when the second turbo kicks in and first turbo seemed fine if under 45 ish. Dump valve and all.

 

I am starting to think maybe O2 sensor? Don't that kick in at a certain speed?

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As I said before it wont be the O2 sensor as once your seeing positive boost the ECU is in open loop, so the O2 sensor is not used for fueling,

Will the engine rev freely or does it misfire/stutter at certain RPM/load?

Seems strange that the ECU was tested and a fault found and supposedly fixed yet its still exhibiting the same symptoms,

Have you checked all vacuum/pressure hoses including the small stuff? as its starting to sound like a boost/air leak to me.

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Just read this off Nic from a post ages ago..

 

"Misfire - 1 or more plugs causes a miss in 1 or more cylinders, this is felt/heard as a hesitation in the revs. A misfire is usually caused either by worn/wrong plugs or broken coil pack connectors, symptoms usually only occur at high rpms/high boost, the car can run fine at lower rpms/boost levels."

 

Does sound like what I have.. How long do plugs last and the coil packs.. Mine are about 8years old because I changed the lot in 2005.

 

Will be looking at connectors today and boosts and vacuum pipes

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Just read this off Nic from a post ages ago..

 

"Misfire - 1 or more plugs causes a miss in 1 or more cylinders, this is felt/heard as a hesitation in the revs. A misfire is usually caused either by worn/wrong plugs or broken coil pack connectors, symptoms usually only occur at high rpms/high boost, the car can run fine at lower rpms/boost levels."

 

Does sound like what I have.. How long do plugs last and the coil packs.. Mine are about 8years old because I changed the lot in 2005.

 

Will be looking at connectors today and boosts and vacuum pipes

 

I did ask you if you had changed the plugs a while ago and you replied yes!, as said the coil pack connector's are prone to breaking and causing a bad connection, but I thought you had said you checked the basics before?

 

You seem to be jumping from one conclusion to another, as David said check and eliminate the other perceived problem areas and the basic stuff before moving on.

Edited by Tricky-Ricky (see edit history)
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