4g61t.org

Hey there,
Ive recently acquired a 1990 lancer ca with a 4g61t motor transplant...
Iam currently in the process of fixing any issues with the motor, i had a check engine light did a voltmeter check on the data link connector which showed code 31 knock sensor, after some help by people on this forum ive found and replaced my knock sensor. Which had ooze coming out of it all the black soft backing was melted, so in other words it was definatly stuffed. I put the new sensor in which i bought brand new from repco, what they sold me which they said would work was a mitsubishi magna tr / ts 2.6 lt & ggalant (what it says on the box) knock sensor.
Looks the exact same, fit perfectly.

I filled the tank with 98ron fuel added octance booster as the guy i bought it from had run it on 91 unleaded...

So after connecting the battery and replacing the sensor, i turned the key, did not start engine, as before after about a min without engine on or with it on does not make a diff, the check engine light turns on.
I disconnected the sensor and it did the same thing as before....

The car seems to run fine, doesnt seem to make any noises, doesnt blow smoke, accelerates fine, does have , idle problem... as in after i run it or after i turn it on it idles at 1500 rpm after dri ing or reving engine slightly, and stopping... five seconds later idle drops to 800 rpm slowly and stays ere until i drive it or rev it agai ...

I also noticed when reving engine quickly the tacho cant keep up and at 4000 rpm stays there for a sec before jumping up to 8000 rpm if i rev slowly it works fine except it seems a slight bouncy sometimes....


Soooo my question is ....
Did i get the right knock sensor...if so what could be causing my check engine light , and how do i diagnose/repair. ... is the knock sensor sensitive to how tight it is? Does it need to be really tight? Or not really...

Could i have an electrical problem?

Whats going on with my tacho?


Any theories or answers and help would be greatly appreciated!

Thanks guys

knock sensor should not be on tight at all. 8 foot pounds.

Check for more codes.

_________________
05 wrx wagon
99 Benz ML 320
91 eagle summit swapped - 6/4 bolt combo
94 Audi s4 - sold
88 Eagle Vista Turbo LX sedan, RIP

Hey just wondering does anyone know if it matters what type of cable to use for the knock sensor, also could my ecu have a fault ? How can i test this

The knock sensor has a "special" shielded wire that is normally brown with a white stripe and decently thick, somewhere around 1/4" total diameter.

The tach jumping about sounds like either an imcompatible coil,tach filter or ECU. The wiring and coil must match the ECU. Google search something like "dsm 90 ECU in 91" or "dsm 91 ECU in 90" and read up.

The car should start and run without a knock sensor. If that is the only code you are pulling from the ECU then I doubt the ECU is blown. Usually a blown ECU yields a multitude of faults. The best way to check this would be to employ an actual scan tool or pull the ECU and inspect for leaking capacitors.

Ok soooo yay i fixed it !!!!!!
What a stuff around!

After searching on the net and not getting 100 percent clear ideas on what to do i reached out to logic and try n see methods.

Heres what i did and found out...

The cable from ecu has to be shielded, this shielding has to be grounded to the chasis.
The power side of the shielded cable goes into the power side for the knock sensor,
the plug ( from ecu to knock sensor not the one from knock sensor)
holds the cables in via a small thin blue rubber seal in back of plug, this is not soldered or crimped.... so in my case i was going to re solder the wires as they were in 2 parts, instead i removed the short bit i had left on the plug by removing the rubber with a small thin screw driver then using pliers i pulled the wire from the plug, i spliced my wire from ecu put heatshrink over the shielded part so no contact with anything else,pull the blue rubber ring over the new cable, then folde
d and twisted my splice to make it thick,
then push it in the plug to make it hold in push the blue ring into the plug as far as it goes without braking it.

Then run a seperate cable from the negative end of the plug to the sensor grounding point of the ecu ( important wont work otherwise)


Thats it job done, make sure you get a good connection and it worked...


Thanks to everyone for your help