2000 celica gts cylinder 4 misfire

[taorge]

Recently purchased 2000 gts with 170k on it...had CEL on when i bought it...
Engine too lean
cylinder 3 misfire
cylinder 4 misfire
random cylinder misfire

After reading a ton of forum posts, I attacked the car from a variety of angles. First I cleaned the MAF...no luck...replace MAF...still nothing...replaced O2 bank 1...lean and cylinder 3 disappearred...gained 100 miles per tank of gas...

good start so far...but cylinder 4 is still misfiring...decided to replace spark plugs...prolly should have done that first but previous owner assured me that he had already done it...well he didnt...original plugs were toast...so after plugs were replaced i also switched the coil to another cylinder to see if the code would move to another cylinder...gained some pep but the CEL still shows cyl 4 misfire...

Anything i may have overlooked?

[RobMilkshakes]

To clear things up, Is the cyl #4 misfire the only code you have remaining?

Also, how long ago did you swap that coil to another cylinder?

[taorge]

also random cyl misfire...when i freeze framed it, it showed only on start up...runs great when warm...switched the coil a few days ago...reset CEL...reappeared this morning showing cyl 4 and random cyl misfire

[RobMilkshakes]

Since you've already taken care of the engine too lean code, that seems to rule out any leak in the intake. With 170k on it, it could possibly be a problematic injector.

[taorge]

that is what i was afraid of...i was more hoping that it would be sensor related as the car seems to be highly sensitive...thanks for your help milkshakes

[RobMilkshakes]

Well its only a suggestion, but honestly, I'm out of ideas beyond that. The gap on the plugs were set correctly, right?

[taorge]

well what i think im going to do is...swap injectors from 4 to a good cylinder and see if the same codes persist...im also going to check bank 2 O2 sensor just in case...i've never had a car as sensitive as this but from reading the forums thats just a Toyota thing, ie being highly tuned from factory

[RobMilkshakes]

Well it doesn't really have a second bank, it would have a Bank 1 Sensor 2. The rear sensor could have some effect on A/F ratio but swapping the injectors would be what I would do.

[taorge]

***update*** hooked up to modus
cylinder is getting proper amount of fuel
tps gave some weird readings though...
upon further investigation i found the wiring harness leading to the sensor had been hacked and spliced...one wire leading directly to main wiring harness of the car...is there a particular reason this was done or was my car the result of a hacker?

[Ace2424]

Originally Posted by taorge

***update*** hooked up to modus
cylinder is getting proper amount of fuel
tps gave some weird readings though...
upon further investigation i found the wiring harness leading to the sensor had been hacked and spliced...one wire leading directly to main wiring harness of the car...is there a particular reason this was done or was my car the result of a hacker?

One wire to which sensor? It's probably a universal o2 sensor if thats what you're talking about. People are not too intelligent and spend money on the cheaper o2 sensors that give you problems down the road. Exact fit is the only thing that will actually work right.

What plugs did you put in? Also, have you simply tried some seafoam in the gas yet? Or running a higher octane... like 89 instead of 87? It could just be a clogged injector.

[taorge]

Throttle position sensor has all wires spliced, 1 running to main vehicle wiring harness
NGK Iridium IX spark plugs
yes exact fit Denso O2 sensor
and the only gas I put in my car is 93 octane

[Bitter]

swap the injectors anyways, just to rule that out. check compression across the engine to make sure 4 isn't a weak cylinder when cold.

[taorge]

ok...switched injectors...reset cpu...code returned the same...
on a side note...does anyone have a wiring diagram with the throttle position sensor on it?