Work Log: DIY Engine Maintenance (Newbie Perspective)
 

NOTE: Formally entitled "Possible fueling issues?"

For the past week I can smell a hint of fuel through the vents if I give it 50% throttle even under 3k RPM.

Throttle lag is one thing, but I'm starting to notice more defined hesitation or bogging under 3k RPM even if I floor it. Plus, power delivery is a bit lacking and feels rough from 50% throttle onward. I have to rev it past 3k RPM to make some power and get it going, but it definitely feels like it doesn't want to open up.

In the past year my engine has died twice after coming to a complete stop (most recent was a few days ago). Engine would idle fairly low or want to drop (closer to 500 rpm). I occasionally have trouble starting the engine (as described in the past), and from reading I wonder if it's vapor lock.

I'm wondering if it's the stock FPR at this point.

Have you pulled codes using Cipher?

What's your wideband show when it does that?

Second the wide band. Sounds like you could be running super rich.

Any exhaust smoke? It might be hard to see unless someone is rollin' behind you to let you know.

Have you checked the injectors? Maybe a bad o-ring? I had an issue with one of mine...

Tune is fairly rich since I never got around to getting a custom tune (out of box GTM tune), but it's making sense. Last year I did see some white smoke on occasion. I freaked out thinking it was a blown head gasket, but it wasn't. I remember seeing it more frequently after ditching HFCs for test pipes. The one time the engine died at the light, I started it back up and it went into limp mode. I thought it was a bad cam angle sensor, but the problem went away and never came back after leaving the car alone. A few days ago I was parking the car and the engine died as well. It was warm out after a long drive, but nothing extreme. I started it back up, and it was fine. No codes.

No odor in the bay. A hint of fuel odor from oil cap. No codes, but I can check. How you guys want me to set it up and give you some logs? Cold? Warm? Idle?

[EDIT] As the car is idling around 700 RPM and ambient of 68F:

• B1/B2 Wideband hovers around 2.1-2.2
• B1/B2 AFR is around 14.5-14.75
• B1/B2 MAF voltage is around 0.65-0.75 V, and there is a split difference of 0.80-0.10.
• B1 Correction 104-107%
• B2 Correction 98-101%

There is some white smoke coming out of the exhaust as the car is warming up, and it definitely smells like it is running fairly rich. In fact, I'm thinking this is always the case for some time. Car is fairly warm with oil temps rising to 145F, and some white smoke is still coming out. Condensation collecting at the tips. I walk back inside and and my shirt stinks now lol.

Do you not have an aftermarket wideband?

IIRC, they're stock. I've not done much with this car after getting the Stage 2 TT setup 45k miles ago.

AFR gauge? No. :p

So you don't have an afr gauge?

No AFR gauge. I need to find something useful and not crazy expensive to integrate to my dash. Future plans is for a HKS boost controller (replacing the Hallman Pro RX MBC) and mount the display along with something like an AFR or combo display to the dash.
[EDIT] Found it: http://zada-tech.com

As dumb as it sounds, what would cause it to run progressively richer? So this is what I'm seeing after 45k boosted miles:

• On the passenger side, where I've already noticed some minor oil residue on the turbo hot side (no smoke), the vacuum hose to the throttle body has some residue, and the same for the PCV. Valve cover seal looks good. Driver side looks clean, but the valve cover is starting to show some minor leak.
• Idle isn't perfectly smooth, but I'm going to attribute this to 45k boosted miles without maintenance listed below.

I do plan on doing some maintenance work in the next couple of months. I'm putting together a list of things to do once the throttles and intake plenum is removed:

• Replace VR38DETT OEM Spark Plugs
• Replace injector seals and o-rings - Do the injectors use stock rings and seals?
• Replace throttle and intake plenum gaskets
• Replace PCV
• Clean throttles, sensors, etc.
• Replace air filters
• Clean and lubricate BOV
• Possibly replace or extend some vacuum hoses

This is just the engineer in me asking since I'm not really a mechanic, and I may start learning how to do some of this stuff with no tuners around. Nearest is probably KC or Dallas. Although there's 65k total miles on the car, I'd love to get it tuned. Just too much on my plate, and it has been a rough year as a new homeowner. The Z has been put in the backburner for the past 2 years. :(

-Phuong

Exhaust leak??


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It'll be tough, but I may try to inspect the exhaust manifold to the turbos the next time my car gets lifted. My car wasn't like this before. It used to take off immediately after downshifting to 2nd. I think it's just running really rich under 3k RPM. Hopefully some of the maintenance work in the next few months will help. Then I need to get the funds to finally get a proper tune.

Smoke test it, I found a leak on my car from header to cat. The oxy sensor would read lean once in a while, the system would dump fuel to try to compensate. You can use a seafoam, but I find the smoke machine works the best.

That's what I'm experiencing. It comes and goes. Perhaps thsts why the idle is not as stable at times. Today was a bit cooler and it wasn't as bad. I'll look into it as I get around to doing maintenance.

Sound like you could have a miss in one of your cylinders. May not throw a code either. I had this happen to me when one of my fuel injector wires came loose. Car felt super sluggish under 3k. Felt down on power.

Yea, it'll be something to look at when I pull stuff apart to change the spark plugs.

BTW... should I monitor AFR from the CAN bus data, or should I get an aftermarket gauge and sensor? If I can rely on the CAN bus data, then it'll save a lot of wiring work. I may get a digital multi gauge with ODB2 input.

I'd always trust an aftermarket wideband over the factory O2 sensors.

:iagree:

Get a wideband bro, there actually really easy to wire.

My wideband has help me diagnose 99% of my problems.

Also, test your vacuum, maybe you have a leak somewhere.

Thanks. So is better to get a wideband sensor and AFR gauge versus pulling AFR Bank1 and Bank2 using Cipher?

Yea, hopefully I can get a hold a smoke machine. I'll get it done after maintenance work.

Yes. Aftermarket AFR is better than trusting the numbers from Cipher

Do any of the 370z even have factory widebands? I remember a couple years of the 350z did for a minute, but then they ditched it.

If the factory o2 sensors are not widebands, the A/F reading anywhere about a half point away from stoich is worthless data.

My 2009 uses standard narrowband o2s.

Do some fuel logs but I can almost guarantee you that one or both of your gtm exhaust manifolds are Cracked causing a Rich condition.... Ask me how I know...

I was going to ask you the very same question after asking you about symptoms. :P Do you hear any high pitched whistling? I've been hearing the faint whistle for the past year, and it seems like it's on the passenger side. Evidently, it is the same one that has a minor oil leak, but not enough to drip. There's no blue smoke. The PCV hose and vacuum line to the throttle has oil residue as well. The driver side is clean. I can only imagine what it'll be like after removing the throttle bodies.

I'll have the exhaust manifolds checked the next time the car gets on a lift.

I remembered this being discussed at one time, and I thought that's what people concluded - that the cars come stock with widebands. I was just curious to see the wide band sensor parameters in Cipher. If that's the case, then I'll consider getting a sensor makeover at some point to go with the digital multi gauges from Zada Tech. Phew... gonna be pricey.

Just buy a digital Innovate. $180 and your set.

One for each side?

Look up EVAP diy smoke machine, you can make one for 10$.

Hook her up to a vacuum line, and watch for smoke :)

You can do that but I'd probably look for a single readout that will read both gauges. With the LC-1/2 you would have to run a second gauge. Most people just monitor one bank. I recommend bank 1 (passenger side) because it seems to run slightly leaner than bank 2. If you don't have the bung in either the downpipe or lead pipe just have a bung welded into the lead pipe of the FI exhaust. A muffler shop should be able to do that pretty quickly at a low cost.

Chuck - I can't recall off the top of my head, but where's your AFR O2 sensor located?

Edit - Innovate makes a single gauge dual wideband but I can't seem to find it any place but eBay for instock purchase so it might be discontinued.

http://www.innovatemotorsports.com/products/dlg1.php

This is the one I run LC-1 with the DB gauge

http://www.innovatemotorsports.com/products/db.php

Kosmic welded a new bung in one of the downpipes.

Before install. That's right.

DIG - I would recommend tapping the lead pipe on the FI exhaust over trying to tap the downpipe in the installed condition.

Currently running FI test pipes.

I have always just run a single wideband, and any time I am on the dyno I will put the dyno wideband on the opposite side just to double check. But for what you are trying to diagnose, both sides might be more helpful.

Don't those have the bungs in them already?

Yea, the O2 sensors are installed to the TPs. Hmm... this is turning into some really good discussion.

I'm going to change and examine the spark plugs while doing some maintenance work. Then I'll get the leak test done and fix any potential leaks. After all is said and done (and hopefully the car still runs), I'll try to see if I can peek at the exhaust manifolds on the next oil change. I'll keep you guys posted in a month or so.

[OFFTOPIC]
Although I can go for something simpler and cheaper, I'm just holding out for something I hope is more useful and permanent. Tuners, please chime in on what you prefer to have handy:

[/OFFTOPIC]

I tried to get some logs last night. In the test run at full throttle I can smell a little bit of raw fuel. Earlier I tried sniffing around the engine bay, and I faintly smell raw fuel from the back of the engine on the passenger side. Isn't that were the evap lines are? I don't see anything.

There's an evap line on the back passenger side, clipped to the intake manifold. Maybe a cracked or disconnected line?

I'll take another look at the evap line tonight, but I don't remember seeing any residue. It's pretty faint at idle. At this point I can feel the heat.

I doubt there would be residue, it would just be fuel vapor, right?

cracked manifolds smell like gas because exhaust is leaking right out, or blown out gaskets in the turbo system. If the manifolds have been on the car more than a couple years, and have lots of miles, chances are really really good they are cracked.

I think you're spot on. It's literally nothing like the fuel leaks in the Z32. HA!

Makes sense. 45k miles on the kit, and it's about 3 years now. At the cost of replacing the CHRA, I might as well sell them and get my hands on the GTX pair and consider switching to external wastegates. It's a lot to chew on... just hoping I can put it off at least a couple of years out.