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Discussion Starter #1
so i am rescuing an 91 turbo mr2. I rebulit the engine, all new everything, and now that she's back together its been hunting down one issue after another. Im going crazy.

so after intalling a new turbo due to blowing oil into the intake. I thought I had it all sorted. it was running great. then the MAP sensor went out, and kept hitting fuell cutoff. replaced the map sensor and she runs good for a few days. then wont start. replaced the EFI relay and she starts up everytime. idles great. ran great for a few days. today, starts right up, idles a little high but steady. but when I step on the gas, she goes up to about 3000 rpm and stalls a bit, then the car starts surging up and down with my foot on the gas. if I take foot off the gas, she idles fine.

I dissonneected the vacuum hose from the MAP, to elinnate fuel cut off, but made no difference. I have tried to see if there is a vacuum leak, but there seems to be no vacuum leak.

I do have a knock sensor error code, and will install a new one. but I had this code for awhile without this weird surging issue. any ideas?

thanks in advance
 

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Discussion Starter #3
yup! had read about that issue as well. just installed a new turbo, so had to rebleed the coolant
 

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so I replaced the knock sensor. and rewired the TPS. the surging is gone! :) but the knock sensor error remains! UGH!

any ideas on possible cause, or fix for a knock sensor error that is not coming from the knock sensor? gotta be a wiring issue right?

so the knock sensor plug has one wire going into it, and then another coming out of it that goes to another plug that is just hanging. no idea where it belongs. and its a weird plug. round with a round male protrusion that doesnt look electrical, but rather like it would be monitoring pressure or vacuum. its on the backside of the engine coming off the knock sensor plug. and ideas? and would this provide a knock sensor error?
 

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so I replaced the knock sensor. and rewired the TPS. the surging is gone! :) but the knock sensor error remains! UGH!

any ideas on possible cause, or fix for a knock sensor error that is not coming from the knock sensor? gotta be a wiring issue right?

so the knock sensor plug has one wire going into it, and then another coming out of it that goes to another plug that is just hanging. no idea where it belongs. and its a weird plug. round with a round male protrusion that doesnt look electrical, but rather like it would be monitoring pressure or vacuum. its on the backside of the engine coming off the knock sensor plug. and ideas? and would this provide a knock sensor error?
Do you have a photo of this? That sounds extremely odd.
EDIT: Is it the TVIS plug?
 

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For the record, the knock sensor wire is shielded. You need to replace it with wire that is also shielded or you'll continue to get phantom knock signals that cause engine to retard.

Clear the engine codes after the sensor replacement and code 52 should disappear. If not, it is an open in the wire. Although there is a small chance the motor knocks heavily and busts this sensor too.

As well, make sure the knock sensor is torqued to spec. 33-ft-lbs. Too tight or loose can cause adverse issues too.
 

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Discussion Starter #8 (Edited)
thanks!

so the wire i replaced was for the TPS not the knock sensor.

so I figured out the extra plug for the knock sensor is due to PO installing the ATS GM knock sensor kit. so now I need to figure out if an OEM will work with the OEM plug which is stillthere, or should I replace the ATS GM knock sensor, which I dont know from what GM car it came from. lots of reading tells me the jury is out on using it, since it might be from a 6 or 8 cyinder and listening for the wrong frequencies. but it was working before.

what I do know is the new OEM has not fixed the issue.
 

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ATS uses a GM one from a 350 cubic inch motor found in a Camaro or Firebird from 1989-1993.
Debate here on using a Saturn one with similar resonance.
https://www.mr2oc.com/61-3sgte-turbo/376437-more-gm-knock-sensors.html#/topics/376437

7kHz GM sensors from the Saturn have part number 21021879. They have a 10x1.5mm thread.


You don't need the thread on adaptor. You can just retap the GM sensor to the Toyota threads. I forget the die you need but it's a common die in most sets.
 
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