SR20DET inconsistent AFRs

[Boosted_ATL]

Ok the newest issue with my SR20DET. Really starting to hate this car, I love it when it runs right but everytime I get it fixed it only last maybe a week before something else is wrong. Well first thing is now that it has gotten cold I start the car in the morning and let it run til the gauge is up to operating temps before I drive. But my AFRs will stay around 10.8-12 for atleast 30 min before it will get up to the 14.5-15 its normally at when cruising. Seems like maybe the engine temp isn't high enough and its running rich? Why would it take so long for it to warm up?

Second issue is a few times a day even when the engine is hot it will idle at around 10, then when I start driving it will stay very rich then get back to normal. I made a video last night where you can see the AFR and Boost/Vacuum gauge so you can see what I'm talking about. Still has 20" vacuum at idle, still gets to 14psi boost. If I close the throttle it will go to full lean while decelerating. In the beginning of the video I had just started the car up and was leaving the gas station. When I pull out it goes very rich 9.9 and hesitates so I let go of gas then it started running better.

When it runs right it has great power, gets great gas mileage, and I love it. But its not consistent. I was thinking it could be from the below freezing temps in the morning, but during the video it wasn't that cold and I had been driving for about 45 minutes.

Car has a rebuilt redtop, MBC, FMIC, HKS BOV (yes its atmosphere vent, but only time I could see that affecting the car is when its open it isn't open at idle or very low throttle driving), Walbro 255, 3" downpipe and exhaust, stock ecu and tune, battery relocated to hatch.

Because of past issues, I have cleaned corrosion out of my ECU, new knock sensor, new ecu temp sensor, cleaned MAF (used MAF cleaner), cleaned out IACV, cleaned throttle body.


Anyway here is the video

https://www.youtube.com/watch?v=dVSIMwBOo18

[bova17]

how new is that walbro?

[Boosted_ATL]

how new is that walbro?

Its a couple years old, but looks perfect hasn't been clogged up or anything. Came out of a different car that wasn't driven much. Its been in the car for about 3 weeks and has been running great. All of this started in the past couple of days it has been really cold. You think the cold weather could be affecting the fuel pump? Wish I had a fuel pressure gauge so I could check it.

I'm off work tomorrow so I was going to double check all my vacuum lines (I'm seeing 20" at idle so I think thats a waste of time but still) and ground connections. Probably going to pull the ECU back apart just to make sure it still looks good also.

[bova17]

Not too sure but if you have a friend that has one try switching it out real quick since its super easy and in the trunk, this was what was wrong with my buddies s14. Thats really the only thing I can think.

[Boosted_ATL]

Not too sure but if you have a friend that has one try switching it out real quick since its super easy and in the trunk, this was what was wrong with my buddies s14. Thats really the only thing I can think.

If I can get my hands on one its worth a shot. I dont really know to many people with 240s though so its not likely I could find one. Pump doesn't sound any different than when it was running good though.

[Kingtal0n]

1. Do a boost leak check (fill the plumbing with compressed air to 15-18psi) make sure you include the pre-turbo intake (inlet) unless it is rubber, in which case it might explode (at 18psi that thing would probably pop)

2. disable your hks ssqv temporarily to see if that does anything (unplug the vacuum source) Only do this once you completed a boost leak check and verified it doesn't leak when closed.

3. replace the maf sensor, check your ECU plug, disable the O2 sensor (unplug it), replace the ECU if necessary

4. if none of the above it must be wiring related, or your fuel pressure regulator is sticking closed, but check 1-3 first, then the regulator, then the wiring.

Also do a compression check, change the oil, change the fuel filter. preventative maint.

[Boosted_ATL]

1. Do a boost leak check (fill the plumbing with compressed air to 15-18psi) make sure you include the pre-turbo intake (inlet) unless it is rubber, in which case it might explode (at 18psi that thing would probably pop)

2. disable your hks ssqv temporarily to see if that does anything (unplug the vacuum source) Only do this once you completed a boost leak check and verified it doesn't leak when closed.

3. replace the maf sensor, check your ECU plug, disable the O2 sensor (unplug it), replace the ECU if necessary

4. if none of the above it must be wiring related, or your fuel pressure regulator is sticking closed, but check 1-3 first, then the regulator, then the wiring.

Also do a compression check, change the oil, change the fuel filter. preventative maint.

1. I do have a air compressor but not completely sure on how to pressurize the piping but I will do some research on that and get it done. Would a boost leak affect idle or light throttle when the turbo isn't spooled?

2. I can do that

3. I tested the MAF and wiring to it with my last set of issues and everything was fine and the voltages seemed fine. But that was a few weeks ago. Will test again. Will disable O2. ECU plug looks perfect and is tight. I don't have a spare ECU but will try to find one.

4. Now the regulator, before I swapped in the walbro I was having some issues with the car not wanting to start on the first time I tried. The walbro solved that issue and it starts perfectly. I assumed it was just the other fuel pump was weak and didnt have the correct fuel pressure. It could have been a regulator issue though and now with the stronger pump its doing something else.

All maintenance is up to date, plugs looked good and fresh oil about 3 weeks ago. I haven't done a compression test but I can do that.

[brndck]

also do you have a dedicated relay and 12v feed for that fuel pump?

[Boosted_ATL]

also do you have a dedicated relay and 12v feed for that fuel pump?

I do not its ran off the stock wiring. I could wire one up with no problems. The battery is right beside the fuel pump in the hatch anyway lol.

[Kingtal0n]

Fuel for the engine looks like this:

AFM -> ECU -> Injectors

Either the AFM is wrong (because of a leak, or because it is bad),
OR
the ECU is wrong (because of a tune (not applicable here), or because it is bad)
OR
The injectors are wrong (because the fuel pressure is wrong (too high), or incorrectly sized (not applicable here))

There are other possibilities of course, such as a bad CAS that triggers the same cylinder twice, etc... but lets not go there until we hit the basics.


not sure why we are looking at your fuel pump, you say it goes too RICH, which usually means too much gas. I would not start off diagnosing a rich issue by replacing/inspecting the fuel pump for weak output.

[Boosted_ATL]

Fuel for the engine looks like this:

AFM -> ECU -> Injectors

Either the AFM is wrong (because of a leak, or because it is bad),
OR
the ECU is wrong (because of a tune (not applicable here), or because it is bad)
OR
The injectors are wrong (because the fuel pressure is wrong (too high), or incorrectly sized (not applicable here))

There are other possibilities of course, such as a bad CAS that triggers the same cylinder twice, etc... but lets not go there until we hit the basics.


not sure why we are looking at your fuel pump, you say it goes too RICH, which usually means too much gas. I would not start off diagnosing a rich issue by replacing/inspecting the fuel pump for weak output.

Alright, well I'm going to start on testing everything you listed tomorrow and see what I come up with. I found a youtube video that shows a guy testing for boost leaks with soapy water like you would test for leaks in a tire. that should work, i know it isn't pressurized the way I would want it to but I cant think of anything I would have to be able to pressurize everything like I would need to.

just seen something using PVC and a bolt in valvestem. Says 1psi of drop per second is acceptable. I could get a pvc cap in place of my aire filter and see what I come up with. That shouldn't cost me more than a few dollars to do.

[Kingtal0n]

You have to use pressure because many leaks will not start leaking until 5psi+
also it allows you to hear the leak. You cannot possibly imagine how difficult it would be to find every leak with soap, imagine there is one under the intake manifold, or under the car below the battery tray.

[Boosted_ATL]

You have to use pressure because many leaks will not start leaking until 5psi+
also it allows you to hear the leak. You cannot possibly imagine how difficult it would be to find every leak with soap, imagine there is one under the intake manifold, or under the car below the battery tray.

Got it, I'm going to get a pvc cap and put it in the coupler right after my MAF and hook it to the compressor. Well just checked weather and it looks like 100% chance of rain so it might not happen tomorrow as planned. I really hope it ends up being something as simple as a boost leak. I love this car when it runs right, but it seems to run like shit more than run right smh.

[Boosted_ATL]

Ok got a update. Got off work started her up and was running 9.9 afr. Popped hood, tried to move bov around to see if it was loose, it wasn't. That shook the intercooler pipe around a little also. Checked all vacuum connections I could see. Moved the line on fpr around it feels stiff but still attached. Unplugged maf tried to Rev motor and it won't Rev acts like it's hitting Rev limiter, and still running rich. Plug that back in say fuck it and close hood to drive home. Get in the car and afrs are perfect. Drives perfect on way home. Only thing I really see now is part throttle under boost afr is in 13s instead of mid 12s like usual under boost. So possible maf plug had bad connection? But it wasn't a constant issue so problem might be back tomorrow. Only time will tell.

[zurud]

Looks like bad o2 sensor.

[S14DB]

You should be able to rev to 2.5K with the MAF disconnected. Stock MAF or Z32? What is your Key on and Idle voltages from the MAF?

The BOV is why it is going rich immediately after the shifts.
Going lean on engine braking is the defuel cycle in the ECU and is normal.

[Boosted_ATL]

You should be able to rev to 2.5K with the MAF disconnected. Stock MAF or Z32? What is your Key on and Idle voltages from the MAF?

The BOV is why it is going rich immediately after the shifts.
Going lean on engine braking is the defuel cycle in the ECU and is normal.

Yea that's about where it sounded like it revved to when Ihad the MAF disconnected. It's a stock MAF. If it's not raining I will get the voltages tomorrow. Yes I know the bov makes it go rich for a second when I let go of throttle. I wasn't sure about the full lean on Deceleration but I thought it made sense glad to know that's normal. But I have put probably 100 miles on the car tonight and AFRs are 13.5-15 idle, 14.5-15 light throttle, mid 13s part throttle boost, high 12s full throttle boost. So whatever I did moving things around and unplugging maf and plugging back in has it running great tonight.