2zz ge help - Engine misfire (shaky) at idle and low rpm, poor mileage, exhaust black smoke, exhaust bad smell

[khalid.rashid1987]

Salaam brothers

2zzge in ee90 corolla since 2018

Normal saada tune done 2 years ago, stock ecu with fpr, custom headers, air n take and downpipe (2.7") and power pro exhaust.

I remember problem started when I changed the car's custom downpipe of 2.7" to 2.2" and exhaust.

Problem is misfire, shaky jerky jolty, sometimes on idle and at times low rpms. On idle one moment its fine other moment the rpm drops from 800 to 500, starts shaking, then to 200 and shuts off, this time its emitting black smoke from exhaust, bad smell and very poor mileage, dropped to half what it was giving me earlier.

Problem started 5 months back with a tiny/unnoticeable misfire on motorway on 2500 rpm. I frequently drive on low rpms. Another misfire after a week. Couple of misfires in a week, went to couple misfires per day, then the car was not actually moving one day, too much misfires, car was too shaky and jolty (jhatke) when I pressed the pedal, in neutral gear it use to shake and shut off. On higher rpms it would be somehow moving, but not quite rough and shaky .

Went to electrician, changed AFM sensor, he changed it form type C to a normal without alphabet. Car was fine two three days, then back again to misfire. Still the normal AFM worked better than the type C till date, I put three other type C sensors but that didn't work.

Checked afm sensor wiring, battery to fuse box wiring, changed air filter, cleaned butterfly, checked injectors and cleaned them for any blockage, checked plugs, checked coils, 02 sensor, changed fuel pump (didn't wanted to).
(everything checked and changed was not in one go)

The car used to get fine a day or two after a component was cleaned, checked or changed, but it would get to misfire again after two three days.

Checked and cleared exhaust manifold leaks, recently changed fpr the old one didn't properly maintained pressure, no improvement even after the change.

Please advise, how can I get it smooth (no misfires) and improve mileage (no black smoke), without visiting the tuner to remap on stock or re-tune (someone advised me to that).

[capsat]

how long you can breath without opening mouth coughing with 1 nostril clipped ??

please 1st thing 1st. for an 1800 cc engine most likely MAF has gone bad due to bad intake.

restore to stock intake. check pcv valve, go for compression test (wet & dry). compare readings with stock 11.5:1 ratio

several issues relate to misfire. vacuum leak, bad injectors, bad ignition coils etc etc

[arslan.v8]

Can you check for error codes? If yes do that. Sounds like you have massive flooding, could be a bad O2 or injectors, or a faulty fpr. The first thing that I would do is to check for error codes and trace the problem from there.

[khalid.rashid1987]

noted with thanks, capsat arsalan.v8

[khalid.rashid1987]

last time I did check for errors twice when it was misfiring, it said the system is running fine, no malfunction. I'll still check it again from another source.

[arslan.v8]

Well I had a car that would do that, it had a swapped motor too, it would randomly start misfiring, running rough, running rich or lean, etc. Turned out, the wiring loom wasn't in great shape with some broken/loose clips and connectors, although everything was wired right, the connectors because of engine/car movement would loosen up, and would disrupt signals so the car would act weird. The loom from the ecu to sensors also had loosing, which caused me similar issues multiple times, also including backfires from the intake. Got wiring fixed and the problems went away. How is your wiring and connectors?

Also one time after a hard pull, the car started misfiring, like it was down on a cylinder. Took the car home and an injector wire had popped out (this is how bad the connectors were).

[khalid.rashid1987]

very right Arslan, wiring is the toughest and neglected suspect in swapped motors, especially when one thinks the part is malfunctioning however its the wiring that is the cause to it. Motors wiring seems to be in good condition, never had big issues since the swap, besides couple of times had a problem of fuel cut when the motor used to get hot, for which I changed the fuel pump twice, however later realized that it was a bad wire patch from ecu to fuel pump.

Recently one of the main wire (70 taara) from the battery to the fuse box had a burnt patch, wherein no current was passing to the radiator fan, lights, horn etc, changed that quickly. This might be due to the humid weather adding to the worsening of wiring setup.

Thankyou for the advice brother, I'll recheck all of the motor's wirings once again, however the first thing to do today is check for the codes as advised earlier, in addition to changing old spark plugs, to rule them out as a suspect to rough idle and flooding.

[khalid.rashid1987]

Faulty fpr was changed with a new fpr, motor is not misfiring that much as it used to misfire on the old fpr, however it still emits black smoke, rough idle and specifically engine shuts off in neutral on traffic stops/brake stops.

[khalid.rashid1987]

I've put Apexi Power Intake in place of stock intake, for less air flow restriction and better filtration.

The first thing I did when I faced the issue was putting a new air filter, checked for air leaks and cleaned carbon buildup in intake valve, throttle body. Would it still have a bad intake? Yes I hear this sound of skkkkksssss skkkkksssss from the intake and right this spur of time the black smoke from exhaust gets more intense and rpm drops on idle from 800 to 500 to 200 and engine shuts off.

Pcv valve, injectors and ignitions coils were checked simultaneously, no malfunction.

Would you still advise me to put on the stock intake?

Compression test and error check would be done today inshALLAH.

[khalid.rashid1987]

Cause of issue was broken heater of the O2 sensor— an overlooked component, though indicated by @arslan.v8 and eventually by DMotorsports.

Appreciate the support.