Engine choking and stalling after hard acceleration

NeoSHNIK

Hey guys, I really need some advice, because my little Z is very sick...

Story:
My car has 55000 miles, mostly stock, except for K&N air drop-in filters and FI exhaust.

1. In January I had two cold starts (long story, but I had no choice...) and I got a Service Engine Soon Light because of that. The codes said - "5th cylinder misfire, 2x Cold Start".
In response I cleaned and recharged my K&N filters (thought it might cause misfire), and reset the battery to get rid of the SES.

2. Car drove fine for 2 months. Then last Friday after a fast turn and acceleration the engine was choking on something. I had pedal to the floor, but the car was going slow and jerking a bit. Engine stalled as I was rolling down a highway... I restarted the engine and it seemed fine after that.

3. Yesterday I got a SES as soon as I started the car, and it read - 0300 - Random Misfires. After some serious forum reading, I decided to clean the MAF sensors and reset the battery. 50 miles later, the SES hasn't came back.

4. I was expecting HP and MPG gain after cleaning the MAF sensors, but instead both were worse. Car seemed slow and MPG was crappy. At one redlight I floored it and after about 65 mph engine started choking, I lost all power and engine stalled. I restarted the car, and it was still doing that even at low rpm. Ended up restarting the engine 2-3 times and finally pulling over. No smoke, engine bay seemed normal. When I looked at the air filters - one of them was dripping with that red K&N oil. The air filter bay had a small pool of oil. So I waited, let the oil drip out. Then I was able to get home and clean the filter from all the excess oil.

Questions:
Do you think the problems my car is having is because of the excess oil in the K&N air filters?

What do I do now? Now that I don't have excess oil, I plan to clean MAF sensors again. But then what? Anything else I should do?

Thanks a lot!!

SouthArk370Z

Probably. Doesn't take but a second for the oil to get from the filter to the MAF.

I'd clean all the intake piping from the filter boxes to the manifold and give the MAFs another good cleaning. I'd also pull/inspect any manifold sensors (eg, MAP). Read the DIYs on TB cleaning before diving in.

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NeoSHNIK

SouthArk370Z, thank you. I found some good posts on TB cleaning on both 370z and G37 forums. Seems like people do it every 25k for fun, yet I've never cleaned mine. It's time to clean TB!
Hate to do that cleaning now with all that pollen outside, but oh well.

Crux

sounds like fuel starve. Was it a right-hand turn?

If so, do you remember how much fuel you had in the tank?

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Justice97

Keep it simple do not unplug the throttle bodies.
Just my opinion.

SouthArk370Z

Welcome.

If you're comfortable cleaning the TBs, you might want to go ahead and pull the manifold for cleaning. If you can't find a good DIY, the FSM will have R&R info.
I wouldn't go that far, but I've gotten pretty lazy.

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Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

NeoSHNIK

It was a right hand turn, but it about half a tank left. Definitely wasn't low.

SouthArk370Z

Doesn't have to be very low. Quite a few have reported fuel starvation with half tank of gas. Several threads on the problem.

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Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

Memphis370Z

This may help guide you along...

NeoSHNIK

Thanks all! Today I bought OEM air filters and installed them. I cleaned TB, although somehow after 55k miles it was still pretty clean. I also looked at the intake tubes and didn't see any oil in them from the K&N.

I put it all back, reset the ECU and drove the Z like it was stolen for 15 miles. Car accelerated really well.
I will monitor what happens. May be the K&N filter was the red herring and I just had bad gas... or may be my fuel injectors are failing. I might put that Chevron Techron into the fuel tank next time I fuel up...

Crux

I get fuel starve with 7/8ths tank left. Hard driving and long/sweeping right hand turns, you'll experience it. Anything under that isn't worth the risk and I won't push the car as hard in turns.

Here's your fix for fuel starve:

CJM Road Race Fuel Pump, Production Round 4

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ban25

Yep, I get fuel starvation after burning only 2 gallons of gas! The CJM road race pump is going into my new build.

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2017 Corvette Z06 7MT | 1LE | Stage 3 | DSCSport

breitwbo

Thanks for sharing this, how long have you had this installed? Any issues? I've seen so much about intakes and they should be installed down by the bumper, Gen 3. What is your view on this installation? I guess the filter cone design mounts right up to the oem hole for air flow. The oem box seems it might be very efficient, any comments from your experience? Are they dry filters?

thanks !

NeoSHNIK

So almost a year later. Turns out the air filter didn't have anything to do with it. Cleaning throttle body and intake aren't solution either.

This is related to gas intake as some posters pointed out. I didn't fix the problem, but I never let me car get low on gas. I reset the trip counter every time I fill up and I try to do it every 150 miles. I've let it get to 200 miles, but its risky. I've stalled once at 210 miles.

Wilson2608

So your saying your fuel gauge is broken and causing you to run out of gas? It may be that the whole pump/ sending unit assembley is broken inside the fuel tank. That's what happened to mine.

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