Engine running rich, stumbling, rough idle after motor swap

[toyubie]

TL;DR Aftermarket/higher flow/non-stock port injectors were installed on donor motor. Swapping for stock solved my issues.
Big thanks to Kodename47, Turdinator, and steve99 for analysis of my shitty data logs and pointing me in the right direction!

Hey everyone, kind of a long story but I'll make it short...

During a clutch replacement, I was careless and did not properly align the transmission before using bolts to pull it towards the motor. God bless aluminum, the block cracked right the fuck apart like a pistachio.

So, the next few months were spent saving pennies until I found a used motor from a trustworthy source, who was upfront about the motor being raced on for a couple seasons, but was running well with no leaks and only pulled to eventually build/turbo.

Motor swap was ridiculously easy (why doesn't every car have an engine harness disconnect???), and aside from snagging one of the camshaft position sensor wires on the front brace on the way in, everything plugged right back in.

It's been a few months since then, but the following issues have persisted, and all my efforts to remedy them have been unsuccessful. I'm about ready to pull the motor and try again from the beginning.

CEL Codes

• P1170 - Port Injector Fuel Performance Does not come on DTC
• P0172 - System Too Rich (Bank 1)

Symptoms

• Car usually requires a pump of the gas pedal during crank to start
• On hot days, or after driving (3-10 miles), motor will idle hunt/rough idle on startup, and occasionally at stoplights
• Through every gear, if the pedal isn't to the floor, motor "bucks" or hesitates/stumbles passing 3-3200RPM. Can be avoided by letting off the gas and feathering past that RPM range (it's my daily driver, second nature by now)
• Slip indicator lights up as well (I understand this is a running rich indicator)
• Cruise control disabled (orange, permanent indicator if pushed)

Attempted Fixes

• Exhaust gaskets (headers, overpipe, front, donut)
• Intake
  • New filter
  • Tightened clamps
  • Cleaned MAF
  • Replaced air box assembly
• Tightened O2 sensors, cleaned connectors
• Re-seated fuel lines, EVAP line
• Checked for other vacuum leaks

So, what's next? Spark plugs? The injectors are from my original motor, but could potentially be installed incorrectly? I'm not sure about the port injection. What steps can I take there?

I've considered purchasing an OFT and flashing a 91 tune to see if there's just enough of a clearance issue with this motor vs. original that my ECU isn't taking a liking to.

A final thought, at the time of purchase, the motor did not have a HPFP installed, so the pump from my old motor was installed. Could I have botched this as well?

Any guidance or thoughts are appreciated.

[Kodename47]

Pumping the gas pedal during start actually reduces fuel. The symptoms are too much fuel. Is the DI ECU connected and grounded correctly to the block. Is the block ground itself good?

Realistically this is going to be one of if the above isn't correct.
MAF Sensor
Primary O2 Sensor
Injectors

[toyubie]

Originally Posted by Kodename47

Is the DI ECU connected and grounded correctly to the block. Is the block ground itself good?

Visual inspection shows all plugs are firmly seated and clipped in place. No loose bolts; I did not see a dedicated ground from the DI ECU. Both motor grounds are also attached.

What would be an appropriate method of testing for a solid ground connection? Continuity test?

Originally Posted by Kodename47

Realistically this is going to be one of if the above isn't correct.
MAF Sensor
Primary O2 Sensor
Injectors

I'll start researching to verify these components, thanks!

[Kodename47]

Originally Posted by toyubie

I did not see a dedicated ground from the DI ECU. Both motor grounds are also attached.

It has 3 bolts. IIRC it's the lowest bolt that grounds it to the block, the other 2 connect to the injector covers.

[Turdinator]

Did you swap the fuel system from your old motor to the replacement motor or just use what came on the replacement motor?

[toyubie]

Originally Posted by Kodename47

It has 3 bolts. IIRC it's the lowest bolt that grounds it to the block, the other 2 connect to the injector covers.

I confirmed that the third lower bolt is secure.

Originally Posted by Turdinator

Did you swap the fuel system from your old motor to the replacement motor or just use what came on the replacement motor?

I did not swap the DI ECU, only accessories (alternator and AC compressor) and the HPFP. Is the DI ECU married in some way to the engine ECU?

[Turdinator]

Originally Posted by toyubie

I did not swap the DI ECU, only accessories (alternator and AC compressor) and the HPFP. Is the DI ECU married in some way to the engine ECU?

I don't know for sure. When I swapped my motor I used the old DI ECU. If you still have it, it would be a quick thing to check but my guess is that since the code you are throwing is port injector related it isn't your issue.

My line of thinking was more maybe the motor you bought had an existing issue with the injectors or even the motor loom?

Do you have any mates with an OFT that could look at your AFRs?

[toyubie]

Originally Posted by Turdinator

I don't know for sure. When I swapped my motor I used the old DI ECU. If you still have it, it would be a quick thing to check but my guess is that since the code you are throwing is port injector related it isn't your issue.

Good point. I sold the original motor back to one of the seller's friends, I'm not sure what state it's in now. Probably rebuilt and getting beat on by now haha

Originally Posted by Turdinator

My line of thinking was more maybe the motor you bought had an existing issue with the injectors or even the motor loom?

Do you have any mates with an OFT that could look at your AFRs?

I didn't see any apparent damage on the loom, aside from the sensor wires I snagged and ripped. I'd imagine if there was any significant damage it'd be throwing more codes or running worse than it is now. Very hard to inspect thoroughly now.

I posted on a local Facebook group to see if anyone would be willing to meet up and log some data for me. In the meantime I'll go at it with a multimeter tomorrow and see if the O2/MAF sensors seem okay.

[steve99]

DI computers are all same no problem swapping


were the port fuel injectors stock on the transplant motor ?


I think you going to have to log ecu parameters like


mafV
maf
stft
ltft
port injector pulse widths
DI pulse widths
AFR
Commanded AFR
to try to diagnose problem


If you see high positive ltft a likely cause is exhaust leak before or near first 02 sensor. this allows fresh air containing oxygen to get to sensor between exhaust pulses at low rpm, ecu thinks its lean adds fuel with positive ltft, but makes car rin super rich at low rpm.


At higher rpm enough exhaust pressure to exclude outside air so its usually ok over 3000 rpm


have a look here


[ame="https://www.youtube.com/watch?v=5WnM_NsOtd8"]Secret of Engine Problem Diagnosis- Fuel Trims Pt.1 - YouTube[/ame]


.

[toyubie]

Originally Posted by steve99

were the port fuel injectors stock on the transplant motor ?

Yes, as far as I know, everything is stock.

Originally Posted by steve99

I think you going to have to log ecu parameters like

mafV
maf
stft
ltft
port injector pulse widths
DI pulse widths
AFR
Commanded AFR
to try to diagnose problem

If you see high positive ltft a likely cause is exhaust leak before or near first 02 sensor. this allows fresh air containing oxygen to get to sensor between exhaust pulses at low rpm, ecu thinks its lean adds fuel with positive ltft, but makes car rin super rich at low rpm.

At higher rpm enough exhaust pressure to exclude outside air so its usually ok over 3000 rpm

I was able to log a few of those parameters through Torque. I watched part one and part two but I'm still having trouble understanding the data I logged:







From my understanding, and this data, it appears the car is running lean? I did not notice the slip indicator come on during the drive; maybe the cool day today is pushing the car in the opposite direction of my overall experience?

Not sure what the make of the O2 data, I chose the two parameters available with voltages.

Maybe someone can take a closer look?

https://docs.google.com/spreadsheets...it?usp=sharing

However, it does appear as though the sensors are functioning correctly... or, at least sending data.

[Turdinator]

Looking at the raw data you have some huge negative trims in places but not everywhere. I definitely wouldn't be going WOT near redline often if I was you, you're running very lean up the top end.

My first thought was that your PI are running very rich but your DI is relatively normal which is causing the lean AFRs as the DI is phased in. I would be triple checking your fuel hoses are all connected in the right way and investigating whether your PI are stock. Can you log fuel rail pressure in for PI and DI?

Also look into making a datazap account. It will make viewing your logs much easier for us.

[steve99]

Its difficult to draw a lot from those logs as you need to know throttle position engine load rpm as well as the other parameters and need them all on one graph.


The AFR look kind of normal but the ecu is having to apply a large negative fuel trim to keep the afr in check. Ie its wanting to run rich but the ecu is applying a lot of negative fueling correction to stop it running rich.


This could be due to a number of issues


if you have another maf sensor available or a mate will lend you one might be worth swapping one in. Check the maf sensor isn't in backwards (not sure if its even possible)


could also be leaking injectors.
or your new motor had larger port injectors fitted.

[toyubie]

I appreciate the input from you guys, it's been very helpful!

Originally Posted by Turdinator

Can you log fuel rail pressure in for PI and DI? Also look into making a datazap account. It will make viewing your logs much easier for us.

Fancy! I enabled logging of all relevant sensors available in Torque:



(http://www.datazap.me/u/toyubie/brz-...=2-3-7-9-10-15)

Originally Posted by steve99

if you have another maf sensor available or a mate will lend you one might be worth swapping one in. Check the maf sensor isn't in backwards (not sure if its even possible)

could also be leaking injectors.
or your new motor had larger port injectors fitted.

What would be a way to tell if larger port injectors have been fitted (would there be a huge physical size difference and what would I compare it to)? In any case, I think the MAF or injectors sound much more likely to be the issue. I haven't found my multimeter, but I can certainly swap out my injectors tomorrow.

[steve99]

Originally Posted by toyubie

I appreciate the input from you guys, it's been very helpful!



Fancy! I enabled logging of all relevant sensors available in Torque:



(http://www.datazap.me/u/toyubie/brz-...=2-3-7-9-10-15)



What would be a way to tell if larger port injectors have been fitted (would there be a huge physical size difference and what would I compare it to)? In any case, I think the MAF or injectors sound much more likely to be the issue. I haven't found my multimeter, but I can certainly swap out my injectors tomorrow.

picture of stock port injectors in link below no one updateds the DI injectors, just the port injectors.


http://www.ft86club.com/forums/showthread.php?t=11242






You rearly need to get someone to diagnose it further before you start spending money on parts, check injectors are stock sure and maybe swap a maf sensor in, but after that you might want to think about a tune shop with brz/Subaru experience having a look




Im thinking it might be port injectors as if you look at the port/direct tables in rom below.


0 means full Direct
then the 30 20 or 50% is amount of Port injection


Your fuel trims are worst when its using most port injection ie around 2000 rpm then it seems to get better as the rpm climbs a bit further and you start using all direct injection