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Mystery Leak? Lean condition


wstefan20

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Have you run a compression test? A burned valve, or excessive blowby can cause these symptoms...might be worthwhile to check.

Yeah. I think I'll do a compression test this weekend. Not blow by, I don't have crankcase pressure when I tested for it. Hopefully it's not the valves. Just had the heads completely redone :/

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Wow! I just love it when a DIY tool saves the day!

A misfire will show lean, because the oxygen didn’t get consumed. Bet a nickel you have an ignition issue, most likely a flaky coil.

I wonder if you have a bad cts? Colder false reading should generally equate to a richer condition though. It might be a good idea to check it with a DMM against a truth table.

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Haha you're fine man, I do that all the time! I put the rear back in with a spacer so it looks good now.

 

I'd take the spacer out.

 

Even though it's set to no report in the tune; it still cycles the converter diagnostics.

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I'd take the spacer out.

 

Even though it's set to no report in the tune; it still cycles the converter diagnostics.

 

The car's been tuned to remove the rear o2, plus the spacer will "trick" the rear 02 into thinking the cat is working so the diagnostics would pass anyhow. That being said, the diagnostics show "passed" with my scantool. If you remove the spacer, it fails the o2 diag.

 

Or am I missing something...? I know you know more about these cars than I do!

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Right; I know it was tuned to have the rear o2 removed...I was there lol.  The trick is null in void whenever the converter diagnostics still run and need to read the sensor.  You spacing it is still preventing it from reading the sensor, fully.  It'll show passed with your scantool because it's set to not report. 

 

That's why Brian said you needed the rear o2 back in it without modification ;)

 

Also; with the coolant leak, I'm half temped to think that either the elbows are leaking only under pressure/load, or the coolant port you opened up under the throttle body is opened too much and the plate isn't sealing around it 100%.

 

Just my thought.

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Right; I know it was tuned to have the rear o2 removed...I was there lol. The trick is null in void whenever the converter diagnostics still run and need to read the sensor. You spacing it is still preventing it from reading the sensor, fully. It'll show passed with your scantool because it's set to not report.

 

That's why Brian said you needed the rear o2 back in it without modification ;)

 

Also; with the coolant leak, I'm half temped to think that either the elbows are leaking only under pressure/load, or the coolant port you opened up under the throttle body is opened too much and the plate isn't sealing around it 100%.

 

Just my thought.

Lol ok, so you're saying that I want to set the trouble code??

 

If the test is passing, doesn't that mean everything's running correct?

 

Idk. You're probably going to have to enlighten me on a kindergarten level as I'm pretty unfamiliar in this aspect.

 

Yeah. I did find some seepage around the coolant port on the side, but put some rtv and there's no new seepage even under load. I think I'm going to have to get an inspection camera since I can't see the rear elbow under load. It passed the coolant pressure test oddly at 15psi.

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Well, on a side note, I did a compression test and I'm pretty stoked with the results. Now, to preface, I used a cheap harbor freight compression tester and I had to remove the o-ring just to get enough threads to even hold. There were only two maybe three threads that actually threaded, so the numbers are lower than they would be with a decent tester. That being said, they all tested within two or three psi of each other and were around 120psi. 

 

Spark plugs were all still gapped correctly and looked like new. Tested for spark and all is good. For sh*ts and giggles, I just bought a fuel injector tester pulse tester, so we'll see how that goes. 

 

One thought I have. My fuel pressure regulator came with a screw in the top and the stock one didn't. I had to install the screw as it had come out and I'm wondering if it might have something to do with the fuel pressure? Everyone is saying the fuel pressure should be around 50psi jumping to 60psi with vacuum removed. Mine is 62psi and jumps to 70psi. That seems really high to me. Here's a picture of the regulator:

 

20180215_215817.jpg

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Not sure if this is also a potential issue, but I noticed that it seems the fuel pressure drops off kind of fast with the key removed. I thought maybe leaking fuel injector so I pulled the rail and tested with the rail out, and absolutely no leakage at the rail. No leak under car, and no gas smell. Strange... See what you guys think:
 
[VIDEO]

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Hmmmmmm.....pinch off the return line to the fuel tank & do your test again......

That's what I was thinking, but won't pinching the plastic lines break them? Can't see a way to isolate the fuel system. Maybe removing the fuel line and "capping" it temporarily? Would that hurt anything?

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Well, blue, you were right about the leak. It's very very slow, but it's leaking out the bottom of the side coolant cover. Strange thing is that I checked both surfaces with a machinist's straight edge before installing the cover. I even used the felpro improved gasket and cleaned the surfaces with acetone. At this point I'm contemplating going with copper rtv and then using jb weld all over the outside. Any other suggestions on this? Really not looking forward to draining the coolant again....

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Well, the plot thickens... turns out I have a vacuum leak again! lol didn't think that could happen with negative fuel trims.... anyways, figured I'd post a really quick video of me doing the smoke test and where it's leaking from. I'll definitely be going with a new throttle body. This one is just too warped. Definitely just using rtv and no gasket this time though. 

 

Good news is I used the same method on my exhaust and there are no leaks! (finally)

 

Still have to take out the o2 spacer. Still not sure how that works, but maybe it'll help. Looks like I have my weekend cut out for me...

 

[VIDEO] 

[/VIDEO]
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Like I said; because in the 01+ cars, it does have to read the rear o2 throughout the converter diagnostic parameters when the car fires up.  If half the sensor is blocked via the fouler it's skewing your pre-closed loop trims.

 

It's pretty basic. 

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Like I said; because in the 01+ cars, it does have to read the rear o2 throughout the converter diagnostic parameters when the car fires up. If half the sensor is blocked via the fouler it's skewing your pre-closed loop trims.

 

It's pretty basic.

Lol thanks again blue. Definitely didn't quite understand that at first. I'll give it a shot and see what the trims look like!
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Lol thanks again blue. Definitely didn't quite understand that at first. I'll give it a shot and see what the trims look like!

 

Wouldn't even worry about it until the TB leak is fixed.  Along with the coolant leak.  I'd be more worried about those than the o2; honestly.

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Well, gasket didn't seal, but just straight rtv sealed fine. Was still concerned about the fuel pressure, so I grabbed one from the junkyard. Fuel pressure dropped to 48 key on engine off and 57 with regulator vacuum removed on idle. Now fuel trims are perfect. Fml. Just say no to any other sensors than acdelco.

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