Big flatspot on Bluetop 4AGE- but I think I might have an idea

Discussion and technical advice for 84-89 AW10 & AW11 MR2. 3A-LU, 4A-GE, 4A-GZE.

Moderators: IMOC Moderators, IMOC Committee Members

User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Hmm, flat spot seems to have come back again.

Error codes:

5 Oxy sensor open circuit
6 RPM signal/no-signal to ecu from distributor ("ne" or "g") after engine has been cranked: distributor/circuit; starter/signal circuit; igniter/igniter circuit; ECU
10 Starter signal (no "sta" signal to ecu until engine speed exceeds 800rpm): vehicle is push started; ignition switch/circuit; ECU. Not a real problem unless it recurs.
11 Switch signals: TPS idle switch off; neutral start switch off (automatic transmission in Drive); A/C switch on; A/C switch/circuit; A/C amplifier; TPS/circuit; neutral start switch/circuit; ECU

Have reset the ECU again to clear the codes. Last time we did this the engine seemed absolutely spot on.

Am guessing this daughter board on the ECU may be the culprit as that's quite a few error codes! Oxy sensor though is worth checking, hope it's okay as know it is likely around £150. :(
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

I would agree there Lauren, there are too many unconnected codes there to be the symptoms of one fault.
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

We'll check the oxy sensor as that's dead easy, once Mark's portable oscilliscope is charged up.
2020 GR Yaris - Circuit Pack :lover:
User avatar
toxo
IMOC Committee
Posts: 11345
Joined: Tue May 30, 2006 5:41 pm
Location: The Toast Aisle
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by toxo »

Potential dodgy wiring?
IMOC-UK - the only club to win 'Best Club Stand' at JAE more than once, and twice in a row!
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Yeah good point. Mark has said he is going to check that as well. What a wonderful Fiance I have. :hug:
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

You can check O2 operation with a basic multimeter Lauren, just measure the voltage on the signal wire, should be switching between 0.2 and 0.8v as a general rule, no need for a scope just to see if it's working.
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

I know, it's just a better way of doing it really as it's easier to see variance in voltage according to Mark. I think Mark likes to get his toys out given the opportunity. ;)
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

I was gonna say, all you need to care about is that it's switching back and forth past lambda 1, the voltages are irrelevant really, but if it's stuck on a single voltage it's screwed, or its heater element is faulty. (4 wire type only)
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Right we've checked it and it's not working. Boo.

But, Mark has found a spare one knocking around in the shed that we can try. :+:
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

Before replacing it make sure the heater circuit supply/earth is working and sensor ground/signal wires are doing their job or no amount of replacement sensors will work.
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

It's a one wire Paul. Mark is going to replace the earth wire. :+:

Thanks for your help. :+:
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

Ah if it's a single wire then that is the signal wire and the sensor earths through it's body so unlikely the signal wire is broken.

Only thing to be aware of on single wire sensors is they take a little while to heat up and start switching so it might appear dead if checked immediately after start up.
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Fair point (I admit Mark knows this kind of stuff better than me). We ran it for around 15-20 minutes or so (starting cold) whilst Mark did lots of tests.

Mark said there was a signal, but not one he considered acceptable.
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

In that case it would appear to be bu88ered. I have a brand new spurious single wire sensor you are welcome to if you need it, it's not genuine Toyota but will do the same job, i bought a load of them years ago for LPG conversions and never used them so you can have one if it helps.

Is it the screw in type or two bolt type?
Image
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Thanks for the offer, though luckily Mark has one that is the same part off his old SC. This fortunately turns out to be the same part number as fitted to late AE86's.

It's the bolt in type. Just need to get a new gasket from MrT.
2020 GR Yaris - Circuit Pack :lover:
JMR_AW11
Posts: 1408
Joined: Thu Mar 03, 2005 12:56 pm

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by JMR_AW11 »

Because the engine is modded and it has a modded ECU you might want to double check the O2 sensor against an AFR meter.

i.e. maybe the modded ECU can't/won't allow the mixture at idle to get weak enough to let the O2 sensor toggle in closed loop.

However, it's more likely the O2 sensor is simply duff :)
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

That's a very good shout actually Jeremy, if the sensor is reading at one extremity of its voltage range that would definately point towards that, i guess if it's not switching and stuck on a middle-ish voltage that confirms the sensor has gone, what were the voltage readings Lauren?
Image
shish
Posts: 251
Joined: Mon Dec 13, 2004 6:11 pm
Location: Manchester, UK
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by shish »

tbh i had considered that the piggyback might be keeping it in open loop and hence the sensor signal not looking like it should (sluggushly moving within a narrow range)

we have a backup (stock) ecu on the way and a spare sensor, so we should be able to figure out whats what
User avatar
Lauren
IMOC Committee
Posts: 38632
Joined: Mon Dec 13, 2004 5:37 pm
Location: Greater Manchester
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by Lauren »

Tried the other oxy sensor, got an even lower reading (in the millivolts according to Mark). So maybe that one is worse than the one we took out?

So, Paul, if the offer still stands for an oxy sensor, reckon I'll take you up on it if that's okay?

Cheers.
2020 GR Yaris - Circuit Pack :lover:
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
Contact:

Re: Big flatspot on Bluetop 4AGE- but I think I might have an idea

Post by PW@Woodsport »

I'll gladly send you a new sensor, however just something to note, not all sensors operate in the 0-1v range, the 3vz-fe V6 Camry sensors operate below 0.1v, is this the sort of reading Mark is seeing? A very low (but switching) reading?
Image
Post Reply

Return to “MR2 MK1 1984-1989 NA & SC”