Kingtal0n

it might be a bad tps. Just unplug the tps and try again to eliminate it as a suspect. The car will get it's info from the maf sensor. If there is no boost leak (test that first!), and the problem does not go away when you unplug the tps + O2, then you are left with only [maf sensor, ecu, wiring, or a leak between the turbo and maf] for the most part.
When you do your boost leak check, try to include the plumbing between the maf and turbo.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

I was thinking it might be the TPS too. I was gunna check it's voltages through out the range.

Do you mean just take it for a drive with MAF only as the ECU's input?

Kingtal0n

yes unplug the tps, and/or O2. try them in sequence, first one, then the other. Or both at once if you want, but issues are more difficult to diagnose when you start making more than one change at a time.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

Tried it. Same exact thing. Maybe it's supposed to run at 16.5 in 4th gear at 2200 RPM steady?

Nikzilla

Once I put the TPS and O2 back in thou, it became worse. It would lean out continuously until my gauge would max out and the car would start dying in a course of 2 seconds.

Kingtal0n

did you test for boost leaks first? Fill the plumbing to 15psi.

Try Resetting the ECU as well. Leave the O2 sensor UNPLUGGED, unplug the battery, Cycle the ignition. Wait a few minutes. Then re-connect the battery. LEAVE the O2 Disconnected and take it for a drive.

It sounds like a bad O2 sensor, or wrong O2 plug / wiring, combined with a poor signal from the maf. What ECU does the car have? #62? Could also be an air leak, but we are going to eliminate that as a possibility because you are going to do a boost leak check FIRST.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

I already did the ECU reset. After I first went for a drive with the O2 unplugged, when it was at 16.5, I stopped for lunch and unplugged the battery.

It's a stock ECU.

And yeah, I'll start building that bloody boost leak tester now.

Kingtal0n

If you get a chance, grab a SOHC maf sensor hotwire. Usually I just goto the local junkyard (U-Pull-it) and grab a few at a time. Get it with the plug because the plug is different slightly. All you need is a Philips head screwdriver, and something to cut the wires with. Dont take the whole maf- just the hotwire portion that bolts into the maf with 2 screws.

Also, when you get a chance, pull out the maf hotwire from your own maf, and clean it. I just use brakeclean but you are not supposed to- they sell special maf cleaner for it.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

I'll do that too, thanks!

Nikzilla

Ok so.

I got myself a can of tomato sauce. That shit fit perfectly in my intake.

Got 2 tire valves, hoses, hose clamps, and a tire pressure gauge. Drilled 2 holes in the tomato can, put the valves through them, sealed them with quick steel epoxy. Took the stem out of one valve, hose on that valve running to the pressure gauge, which has it's spring mechanism taken out. Everything is hose clamped. Took out the MAF/pod filter combo and put the tomato can in there and clamped it.

I couldn't find my old bike pump so I just used the tire inflator that comes on my battery jumper. I let that sucker run for 10 minutes straight, the pressure gauge didn't even budge. I couldn't feel any air coming out of anywhere, it all seemed air tight. I even took out the tomato can, put it to my mouth and tried to blow. It's air tight. I pulled the vacuum hose of the wastegate, and I could just barely feel the air coming out. I had to lick my finger just to feel it.

Does the tire inflator just suck? Do I need to use a bike pump?

I'm also gunna hook up a paint can with a burning rag in it between the tomato sauce and the bike pump to get smoke in the system.

I also took the opportunity to clean the MAF with MAF cleaner spray. It didn't look dirty at all thou.

Mikester

Ya know what I think? I wonder if you verified the condish of your plugs after all that running lean. A 'stumble' at certain levels but good all in/all out good be as simple as shitty plugs.

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DashS13

my sr started doing the stumbling and hesitation after i installed the s14 sr turbo inlint. Maf is stock, and its mounted directly on to the inlit itself. This hesitation is around 2500-3000 rpms, and it stops after i open up the throttle body a little more. checked the plugs out and all were good, but it just dies and i can smell unburned gas without even getting out of the car

Nikzilla

I actually did check them and regap them right before I went for my first drive when I got the car running. They looked just fine. I gapped em to 0.032in. I'll check em again today. The lean could have indeed killed em.

That sounds strangely similar to my problem. Can you describe what was the cause in a bit more detail please?

Mikester

Couldn't hurt to swap them out. Try gapping to .030.

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DashS13

unfortunately i have yet to find the cause. i have been ignoring the diag screw on the ecu due to not having a precision screw driver handy, mine honsetly feels like more boost leak related. my car recently started dieing after high revs and the bov lets off, gonna check the recirculation on that also if diag screw takes me no where, also started doing this when the temp out side was average of -15 in the morning...dont know if thats a huge issue or not

Kingtal0n

1. we usually just use a small piece of pvc with a single hole for the tire valve



2. You need to use an air compressor and verify that the plumbing builds 15psi of pressure, and holds it there.

3. Points of interest when doing your check:
a. the hose that runs from the turbo inlet to the valvecover can be blocked with a large black marker, use a hose clamp
b. put the PCV in place of the maf. use the maf clamp to seal it up. No need to use sealant or anything liquid anywhere when doing this.
c. use a tire valve so you can do this anywhere you would normally fill your tire.
d. If the engine is stopped in such a way that both an intake and exhaust valve is open simultaneously, the air will leak right out into the exhaust (because it will flow through the IACV). If at first you see no pressure building, listen in the exhaust for airflow, then bump the engine slightly to move the valves closed.
e. alternatively to d., you can remove the hose from the IACV and block that as well. But this is not recommended because that hose is usually very difficult to remove without taking off the cold pipe.

And I may have forgotten something. I've been driving an N/A vehicle for a few months so my turbo instincts are corrupt. XD

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

Ok, I found a massive fucking hole in my intake right behind the MAF.

Wtf is this hole?



I'm gunna seal it up for now.

P.S. Ditched the tomato sauce, tried again with chicken noodle. Confirming Chicken Noodle is best for finding boost leaks.

Nikzilla

Ok well I did a super professional job of sealing it.



Brb gunna pressurize the intake again.

Nikzilla

I still couldn't get pressure into the system, so instead I hooked up my chicken noodle soup to a paint can and burned an oily rag in there to create smoke, and then pumped it into the intake. No smoke came out, but I still couldn't pressurize it (I think my schrader valve seals are letting loose under pressure), however, when I pulled a vacuum line off, a significant amount of air pressure came out, which means that the system does indeed hold pressure!

Kingtal0n

no, dont cop out. you need to hold 15psi in there. Something starts leaking at 2psi you cant even hold 1psi of pressure thats not a good sign. Some leaks wont even show up till 5psi;

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

Ok, so I took her for a test drive.

She's dead on! It seems like that hole was the only issue remaining.

60mph cruise, 15.5 afr, high RPM pull, dead on 11.0 afr.

Awesome!

Thank you guys for helping me pin this sucker down!

Nikzilla

What's leaking isn't the car but my boost leak tester. I couldn't find any PVC endcaps that could fit, so I had to use food cans. I tried my best to seal them as good as I could, but under pressure they still break loose.

If I want to test it to 15psi, I would need to find 2.5inch PVC endcaps somewhere.

Mikester

Glad you found that hole... Sucking in un-metered air is never a good thing.

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Nikzilla

Ok, looks like I'm not quite done yet!

Patching up the hole did help. Before, my AFR at WOT at 5k+ RPM was 12-12.4. Now it's 11.0.

However, I was still disturbed by the 16.5 5th gear 100kph cruise, as I read that it should be about 147, and sometimes it would stumble hard (jerk the car a lot) under half-throttle at about 2500 RPM up until it would boost. So I decided to plug my O2 back in, because I thought that it would trim the fuel map and smooth out the car.

After driving it for 2 hours with the O2 plugged in, it gradually leaned out the car, making it worse, and the problem came back where it would lean out to 20+ under very light throttle. It became very hard to drive as I had to pulse the throttle on an off to use the fuel enrichment to richen the mixture. So I unplugged the O2, and cycled the ECU (disconnected battery for 30min). It became drivable again, albeit still at 16.5 on the highway.

Now, I'm 70% certain that I destroyed the O2 sensor while making the car run right. My other 20% is set on another vacuum leak. 10% uncertainty.

What do you guys think?

I ordered a consult cable, and it should be arriving this week. I don't wanna potentially replace a perfectly good O2 sensor, so I'm going to wait and abstain from driving the car until I can see what's up in DataScan.