Car is driving me insane. Misfire cured - now has a rough idle and lacks power

[jsdub1]

Ok, here's the story:

Car: 2000 GT-B e-tune 5 MT

Car is imported in June, runs great.

Timing belt / water pump done right after import.

Car slowly started to develop hesitation, weak acceleration end of october. I suspected a vac leak and checked quite thoroughly for those spraying tons of contact cleaner around all the parts of the intake system. Nothing. boost gauge holds ROCK steady at 17inHg at idle. Other than the hesitation, no problem.

This develops into occasional misfires. I can feel the engine go "bump" - the car shakes slightly, every now and then at idle. Car will also shudder under boost in twin mode. Only tested it a couple times, because I didn't like how i felt - was around 4-6k rpms. problem was intermittent. Sometimes it would happen, sometimes it wouldn't.

Then the same judder / mis under boost also happened in single mode - 2.5 to 4k rpms under light to mid throttle. Misfire at idle is now much more frequent, although still random. does not seem to follow any rhyme or reason. A few put put put put sounds here and there , for a minute, then stops for the rest of my drive. Other days it would be almost undriveable because of the misfire and hesitation.

Then, on cold start, the car would not want to go anywhere. As in, i would give it throttle and it would want to die and buck hesitate violently. Violently. Would give it throttle but it didn't seem like the car was getting any fuel. I would let the car idle for a few or drive very slowly for a few blocks and it would sort itself out. Idle was smooth, even when that was happening. This issue never persisted when the car was warm.

Anyway, it kept getting worse and I had the injectors cleaned and flow tested, one was quite drippy and after reinstalling them, the misfire was gone! WOO RIGHT??!

WRONG

I put about 60kms on the car - misfire free - I was very happy to finally have this issue resolved after a month. I was driving my misfire free car - it was idling great and running generally as well as it was before all this started. The hesitation after cold start remained, but I chalked it up to a mis calibrated TPS. I went inside the bank to deposit a cheque and came back out to my car. I started it up and something was different. VERY rough. I thought it was the cold start hesitation issue still. Nope, casr began to run very rough, almost like it's on three cylinders. Would smooth out at higher rpms but idle was atrocious. Shaking car.

limped it home as I was only a couple of minutes away.

Swapped on a new throttle body with a calibrated TPS and fired it up. Kind of rough, but better ish. Drove it around a bit. Parked and turned it off. Went into a shop. Came out and the car would not stay on. It would start and then idle for about 5- 10 seconds then peter out and die. No CEL. I tried about 5 times. No dice. I unplugged the Coolant temperature sensor and tried and the car fired up, very roughly.

So that's where I am today.

Car has:

HKS axle back

Blitz SUS pod

Refurbed solenoid box

new vac line throughout bay

Boost gauge.

Silicone turbo -> intercooler pipes / coupler

Line 10

Line 1

Stock other than that

I have replaced or tested the following potential causes when I was hunting for my misfire gremlin

- plugs NGK BKR6EIX - gapped to .6mm

- Coil packs (swapped with known working, and back, same conditions)

- tested for vac leaks with contact cleaner - boost gauge holds -17inHg

- MAF - swapped with known working, same conditions.

- injectors - cleaned and flowtested

- compression test - 147 all 4 cylinders - 6 cranks tested each twice.

- burped coolant system (no bubbles), coolant also recently changed - subaru oem

- new TPS - same conditions

- inspected plugs after around 1000kms - carbon fouled, no oil

- o2 sensor - same conditions with sensor plugged in or not

- cleaned all my engine grounds

- inspected fuel pressure regulator, no fuel in vac line

- no oil in coolant

- no coolant in oil (recently changed)

- no bubble in coolant on cold start or warm

- ran seafoam cleaner through tank, crankcase and upper engine

- new knock sensor - no change

pending items

- fuel filter on order

- coolant temperature sensor on order

- test fuel pump voltage drop

Are there any other diagnostics I could run cheaply before I take the nuclear option and just buy everything it could possibly be? Does this jump at at anyone as something? Honestly I used to love this car but I am coming to hate it. It's getting quite cold here in Canada. Can you help me love my baby again?!

Edit: NO CEL or stored codes

Many thanks for your time and replies,

J

Edited November 26, 2015 by jsdub1

[Marky]

I was like "yep, AFM" until you said you'd ruled it out. It very very commonly dies on this model and is not consistent in how they fault out, more often than not there's no error reported either

When you unplug the 02 sensor does it give a CEL for it?

[jsdub1]

Hi marky

No CEL for o2 sensor when unplugged. Car runs the same with / without

[loner]

How long ago did you have the compression test done? Have you also had a leak down test?

[jsdub1]

compression was done maybe 2 or three weeks ago. I think I got it figured out though. I was initially going to ignore the injectors since I just had them cleaned and tested and they came back OK. I was inspecting FPR and replacing gaskets last night and I thought I'd double check injectors / other connections etc. turns out the one they mentioned was drippy during the test died completely. No change to idle when I pulled the plug. moved it back one cylinder to confirm it was the injector and not the electrical connector. thank goodness. found a matching set I'm going to pop on in today and then go for a spirited drive.