Hello & 4AGZE Power Cut Out!

[elliott_knight]

Hello Folks,
I am new to the forum as I have recently done an engine swap where I have fitted a 4AGZE engine from a corolla into my NA MR2 MK1. Most the swap went very smoothly, I thought I was one of the few people to do an engine conversion with no Hick-ups. BUT! once it was all done, all parts in place, wiring all set up I have running issues.
For a week the car was running with no boost until I realised I was missing the SC relay... Found that in a box of parts and thought that was it, but again no.
The current problem is unknown, I have a problem where the engine cuts-out under hard acceleration, after a little research it looked like I had what people described as power-drop with the difference of my power drop happens anywhere above 2500rpms the it cuts out and starts to spit and splutter until it kicks in again catching you by surprise, then cuts out again.
I unfortunately haven't had the pleasure to feel the SC do its job and its becoming very frustrating as I haven't been able to solve the issue for the last few weeks and I have a track day booked in a couple of weeks
after reading peoples posts with similar issues I believed it was the knock sensor, or closer inspection it broke.. So I though to myself at least I know what it is, I bought a new sensor original Denso part, fitted it, engine management light off so I got exited BUT... Again same problem with the cut outs!
I tried something I read from a member of this forum where I removed the knock sensor from the block and wrapped it with wire then earthed it, but this didnt work, the engine management light would come on and the same problem was there.
I need some help as I am really running out of things to try.
The things I believe it could be are: knock sensor (still don't want to completely count it out), Timing issue or possibly the O2 sensor? Can an O2 sensor cause so much havoc?
The weird thing is this only happens when the SC is connected, when I need to go to work I disconnect the SC and the engine runs fine (apart from not being SChargerd)
I'm sorry I've gone on such a rant but I really am lost and it seems this forum is where people have more knowledge.
Cheers!

[Hiro]

Do you know if the 4AGZE originally came from an AE101? If so they are notorious for the ~5500rpm power cut, from memory it is low-octane fuel (damn Japan and their 100 RON) combined with an over-sensitive knock sensor. Not sure why it would be happening as low as ~2500rpm though.

This from a member with a fair bit of experience with the issue

Pow! Welcome to the fun of the AE101 GZE.

My AE101 GZE runs without the powerdrop 90% of the time, the other 10% it's barely noticeable, and it's usually on a hot day, when I'm wearing odd socks or the planets are aligned.
So far, I've installed a 7MGTE (IIRC) Knock sensor, an AE92 ECU (less sensitive knock circuit) and that may be it... You'll also need the plug for the 7MGTE knock sensor as it's different to the 4AGZE one. Oh, and the AE92 ECU has a slightly different pinout, but my site in my sig has the details.

I'm planning on maybe building a filter circuit that filters out all but 6400Hz (knock frequency in the 4A engines) to minimise extraneous noise from reaching the ECU to help prevent it from freaking out.mIt would be an inline module that you hook in with a power and ground too, Basically an active bandpass crossover.

It seems that in the AE101, the knock sensor circuit was made more sensitive due to the higher compression and boost, but due to harmonics from the supercharger (it is believed) the preamp in the ECU overloads at 5500RPM from the extra noise and the ECU freaks out and pulls timing. Kind of like yelling into a microphone (the knock sensor is just a piezo mic).

I would like to get my hands on an AE101 GZE ECU, so I could trace out the knock sensor circuit and compare it the my AE92 GZE ECU. That way, it might be possible to insert a gain control like on an audio amplifier to cut down on the overloading. Or maybe have a zener diode to shunt any over voltage to ground... hmmm.
I just need an AE101 GZE ECU for a few days...

[maj]

Have you tried putting it in diag mode to see if it throws any error? Depending on whether you are using an AE101 (smallport) or AE92 (bigport) GZE, you could still have the incorrect sensor, which will be fully retarding timing all the time, which might explain your issues with it coming on much earlier than the usual 5,500rpm issue as described with the knock sensor.

The ECU light might only have detected the sensor missing (due to it being broken), but if its the incorrect sensor then you might have error codes still every time it gets a reading it was not expecting.

Timing could definitely be the issue. The rear O2 sensor (post cat) should not give that kind of output; I've driven mine around with it disconnected when my exhaust broke, the front O2 sensor it might be a possibility, but it seems more likely still to be either timing, or knock sensor (which is essentially retarding timing).

Not sure how the SC could be affecting this either, someone with a little bit more knowledge on the SC/vacuum circuits should be able to assist.

I'd also appreciate if you have the part/model number of the Denso knock sensor handy. I'm currently halfway through rebuilding my bigport GZE and am in need for a replacement sensor, I have found a few aftermarket ones but yet to find a Denso part at all.

[elliott_knight]

Have you tried putting it in diag mode to see if it throws any error? Depending on whether you are using an AE101 (smallport) or AE92 (bigport) GZE, you could still have the incorrect sensor, which will be fully retarding timing all the time, which might explain your issues with it coming on much earlier than the usual 5,500rpm issue as described with the knock sensor.

The ECU light might only have detected the sensor missing (due to it being broken), but if its the incorrect sensor then you might have error codes still every time it gets a reading it was not expecting.

Timing could definitely be the issue. The rear O2 sensor (post cat) should not give that kind of output; I've driven mine around with it disconnected when my exhaust broke, the front O2 sensor it might be a possibility, but it seems more likely still to be either timing, or knock sensor (which is essentially retarding timing).

Not sure how the SC could be affecting this either, someone with a little bit more knowledge on the SC/vacuum circuits should be able to assist.

I'd also appreciate if you have the part/model number of the Denso knock sensor handy. I'm currently halfway through rebuilding my bigport GZE and am in need for a replacement sensor, I have found a few aftermarket ones but yet to find a Denso part at all.

I went againts all the rules when I bought the engine, it was all in bits stored in boxes and bin bags as the seller had it stored in he's dads loft! I couldn't help myself 4agze engines are hard to come by in the UK and looking at the custom piping made for the intercooler and some mods made to the abv and the oversized pulley gave me a a good idea who was the previous, previous owner of the engine. Her name is Lauren and she is quite well known in the UK MR2 circle.
I didn't notice the knock sensor being broken till a week ago when I went to inspect it and half of it came apart when I disconnected the plug. I thought my engine was a AE92 but its a small port so I suppose its a AE101 then which makes sense after these issues.
There's a very good Toyota part supplier that specializes in MR2s, Supra's and Celica's which is based in the UK and had a very similar sensor which was designed for the MK2 but had the same plug, after some research lots of people said most Toyota knock sensors from that time send the same frequence therefor I thought it would be compatible... Maybe its not? Doesn't matter now as today when I went to test the sensor outside of the block I dropped it and broke it! I would have probably got pissed off if I haven't have had so many disappointments in the last few weeks lol
Maybe it wasn't the right sensor in the first place?
index is the website I got the sensor, if there's something you need let me know and I will get it sent to my house and from there I will post it to you to avoid high postage charges (I don't believe in making money on fellow car enthusiasts)
The new sensor was pretty much identical to the original but had a slightly longer thread and different part number...
I haven't tried diagnostics since as I thought the engine management light needed to be on for it to read any errors?
Thank you both for your imput

[Hiro]

Late-model AE92s were also smallport GZE but I don't think they suffer it anywhere near as bad.

[maj]

If it's smallport then you might have a better chance of using a later model knock sensor with the matching plug then. The bigport GZE is a bit more troublesome to find a sensor for as it is the only bigport that came with such a sensor. As Hiro pasted it is also quite possible the sensor circuit may be different for the smallport vs bigport. TERRA might have the answer. It is possible I am wrong and the sensors are all swappable with their matching plugs, but it's still an unknown risk.

In regards to the CEL, I can't 100% confirm because I haven't played with the smallport GZE or it's ECU, I only know the factory GZE AW11 ECU's. At the very least you should be able to put it into diag mode, and if you get a constant, uniform flashing of the light (every 1.5sec), you at least know there are no diag errors so it would be something more mechnical rather than a dud sensor.

You definitely are in a hard place and I feel for you. My only other thought that would benefit you in the long run, would be to find a reputable tuning shop who have a recommended aftermarket ECU and have experience using them on 4AG's, that way they can verify the raw input from your sensors is what they are expecting and work with it. The 4AG stock ECU's hit a brick wall very quickly when you are looking at doing any kind of solid power upgrades, such as spark, fueling or timing.
An example is a member here, Gun Metal, is running an AE101 GZE conversion in his AW11 and with some good old fashioned tuning along with a decent aftermarket ECU, is putting down a very respectable power figure whilst still using the stock SC12 supercharger.

[elliott_knight]

If it's smallport then you might have a better chance of using a later model knock sensor with the matching plug then. The bigport GZE is a bit more troublesome to find a sensor for as it is the only bigport that came with such a sensor. As Hiro pasted it is also quite possible the sensor circuit may be different for the smallport vs bigport. TERRA might have the answer. It is possible I am wrong and the sensors are all swappable with their matching plugs, but it's still an unknown risk.

In regards to the CEL, I can't 100% confirm because I haven't played with the smallport GZE or it's ECU, I only know the factory GZE AW11 ECU's. At the very least you should be able to put it into diag mode, and if you get a constant, uniform flashing of the light (every 1.5sec), you at least know there are no diag errors so it would be something more mechnical rather than a dud sensor.

You definitely are in a hard place and I feel for you. My only other thought that would benefit you in the long run, would be to find a reputable tuning shop who have a recommended aftermarket ECU and have experience using them on 4AG's, that way they can verify the raw input from your sensors is what they are expecting and work with it. The 4AG stock ECU's hit a brick wall very quickly when you are looking at doing any kind of solid power upgrades, such as spark, fueling or timing.
An example is a member here, Gun Metal, is running an AE101 GZE conversion in his AW11 and with some good old fashioned tuning along with a decent aftermarket ECU, is putting down a very respectable power figure whilst still using the stock SC12 supercharger.

Thank you for your imput, I will order the same sensor as I did last time (before I broke it) and I have several numbers of tuning companies in the area that offer remaps and ecu tunnings, there must be one person there that knows about Jap cars!
thank you!

[JDM hachi]

Check your map sensor, you may not have the correct one if the car runs ok with no s/c (or no positive manifold pressure), connect the s/c to full time power and see if the cut out problem still exists. But of most importance, put the thing in diagnostic mode, then check any sensors/wiring to sensors if a code is pulled. I have a feeling the tps may need adjustment, after all if it came in a box of parts you probably just screwed it on, check a service manual and that will tell you how to set it up....There is literally 100's of things to check, start easy then start pulling your hair out!!!

Good luck with it, there is a massive knowledge base here at Toymods, and i think a solution will be found, and be a lot easier than expected.

cheers,
matty.

[elliott_knight]

Another thing I found broken was the map sensor. I managed to bond a copper tube on to it but when the issue first appeared I thought that could be it so I got a new one from a member of imoc.uk and much of the same. I have also run the SC directly off of the battery and the clutch engaged but the running hadn't changed.
I'm now waiting to get the new knock sensor, will probably get it on Monday now but will give some garages a call that do engine remaps see if they can help me. My knowledge of remaps is limited, will a remap benefit me with this issue or do I have to look at getting another 4agze ECU from an AE92?
Thanks

[elliott_knight]

To clarify would this be the supra sensor which would be recommended?: Just arrived in New Engine Knock Sensors Denso they manufacture for Toyota
Fits Celica ST 205 GT4, ST 185 GT4 ,ST 202, ST 183 (3S-GE engine) & V V T I (1999 onwards)

Supra 3.0i JZA 80 N/A & Turbo Models (1993-1999)

MR2 Mk2 (3S-GE) & Turbo Models (1992-1999),MRS Roadster (1999 onwards)

Part number: QIC 917

The new one I have is this one which has the same plug:
Fits Celica ST 185 GT4, ST 183 & ST 182 2.0 3S-GE engine (1989-1992)

MR2 Mk2 SW20 (3S-GE) & Turbo Models Rev 1 (1989-1992)

Part number: QIC 916

[elliott_knight]

Never mind it's all over, it was a problem with the map sensor. Thank you all for your input.