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.