Some sudden issues with my 24vT

[DannyLo]

Somewhere in between parking the car Sunday night where it was driving completely fine under power, until the next morning, something happened.

I'm trying to figure it out, but I haven't really had the time to get under the hood or log it. Just to scan the car, so I figured since I can't look at it tonight, i'll post up and see if I can get leads so I don't waste time tomorrow.

Scan revealed 3 codes. Random misfire, Intermittent Mis-3, Intermittent Mis-6.

As far as driving, it is completely normal out of boost, idles at 14.7ish, cruising AFR is same as usual, and its not until i get a little heavy with my foot that it acts up.

It feels like it has no power, and the tone of the car when i get into the throttle tells me it's probably pulling timing.

MAF/O2?

Sorry, I know this post doesn't give alot of info...

Tomorrow I should know some more if I can get to log it and check under hood that nothing is loose or out of place.

[24vGTiVR6]

Scan revealed 3 codes. Random misfire, Intermittent Mis-3, Intermittent Mis-6.

As far as driving, it is completely normal out of boost, idles at 14.7ish, cruising AFR is same as usual, and its not until i get a little heavy with my foot that it acts up.

It feels like it has no power, and the tone of the car when i get into the throttle tells me it's probably pulling timing.

I had similar symptoms, except my AFR was all over the place. Turned out to be valves. It sounded like a modded WRX and lacked power. I was running 18psi on a stock motor at the time.

Seems like VRT's are falling from the sky lately.... ginster, me, you..... good luck dude hope it's nothing crazy.

[DannyLo]

car sounds normal, and drives normal out of boost; it's just pulling timing like mad when i step on the throttle causing it to have no power.

I can't imagine the engine being on its way out. It hasn't ever seen more than 10psi yet and it's at 9:1 compression...I never finished my fuel pump so I couldn't go any higher. Ran a year before that at 7psi on stock compression.

Started thinking about it a bit tonight, and have a suspicion that it might be related to the DV. I'm running a regular Bosch OEM DV and I'm wondering if the diaphragm inside has ripped and it's looping boost back into the turbo.

Hopefully I'm right, but we'll find out tomorrow

[PjS860ct]

How old are the plugs?

[DannyLo]

How old are the plugs?

A year or so, same with coils. I replaced them all.

Diverter valve checks out. Seems like its intermittent now. I'm wondering if the Jersey fillup before driving home from WF gave me a batch of bad gas.

[DannyLo]

Alright... ran that tank dry, filled it with gas that I know is good, and it still is down on power/pulls ALOT of timing, even at 7psi.

I haven't logged it, but I did a 3rd gear pull, and looked over at the computer and was seeing CFs of 10+ across the board, so I stopped.

About to scan it for codes to see if any codes have come back...

edit: No codes have come back.

[DannyLo]

Ok, some progress. One problem fixed, but another still remains.

Turns out my DV was leaking boost. I changed it out for a new Forge, and it's infinitely better. I noticed that my old bosch valve wasn't seating properly when closed.

Now, what remains is a sort of lean condition.

In boost; this is only 7 psi mind you, I see this:

2nd gear = 11 - 11.5 AFR
3rd gear = 12 - low 13 AFR

Haven't gone any further. Car feels doggy, like it's not happy/pulling timing, etc.

Also, I'm not sure if it relates to that lean issue or not, but if the car's warm and I try to start it...after going to gym, for example, it doesn't want to start unless I give it throttle. It cranks over and lazily hangs around like 200-500 rpm, and then stalls...unless I blip it properly. If I blip too much, it bogs and stalls. Has to be perfect amount of throttle as it starts to turn over and then it will fully start and idle normally.

It's not the throttle body. I've checked it, it sits where it should, and has been aligned, and reads normally in VAG-COM. Doesn't change a thing.

I seem to always have weird gremlins

Fuel issue?

[DieGTi]

I've lost count... is this your third dv now?

Have you cleaned your MAF sensor lately?

[DannyLo]

I've lost count... is this your third dv now?

Have you cleaned your MAF sensor lately?

Something like that

And no, I haven't...I guess I could take a stab at that.

[DannyLo]

Some videos about the startup, and lean issue on a cold start.

In this video, it starts, and hangs around 400rpm for a sec...then suddenly snaps overcompensates idle and then settles down to where idle is set...but lean

[Sometimes, it will sit at that 400rpm crap for as much as 5-10 seconds before it snaps up, overcompensates and settles down to idle. (You can see that when it's idling around 400, vacuum is not right as well)]



Then, in this part 2, it will continue to idle lean, at slightly less than ideal vacuum, until it is "warm" where i guess o2 takes over and it goes right back to relatively stoic at idle, with normal vacuum.

(kind of long, skip to 2:00 to see when it changes)

[2DR16VT]

Do you think perhaps it could be the crank angle sensor is faulty ?

[spitfire481]

sounds like a maf problem. my buddies 12v vrt was having similar issues at idle (low vacuum, lean, etc). unplugging the maf caused it to idle much better. see what happens with the maf unplugged.

[DannyLo]

Here's some data for you guys, with a video. They are both from the same event. You can basically follow the timestamp on the data with the video once the car starts pretty closely. I graphed a few things against time from startup to end to get a visual.

I'll link the data, because it's kind of big to directly post:

http://i158.photobucket.com/albums/t.../ColdStart.jpg

And the video to go with that data:



Cheers
-Dan

[DieGTi]

Lazy MAF... all day long. That's where my money would be.

[DannyLo]

Lazy MAF... all day long. That's where my money would be.

Even though the MAF readings at idle are within spec?

[DieGTi]

On the 24v the IAT is built into the MAF sensor... if the sensor outputting hotter than actual then it will trim the fuel lean. Clean is easy to do or if you have a spare to swap in to eliminate the possibility.

[DannyLo]

ahh I didn't even think about IAT. I could do an air temp reading on startup and driving as well, but I think I'm just going to replace the MAF with a new one. It's still the original one from when the car was new. I'm sure it hasn't been very happy being 1.5" from the air filter for the last 2+ years.

Plus being that now I'm finally going to raise the boost after I sort this all out, since my new high flow in-tank is in, I figure a new MAF wouldn't hurt.


Engine Shot by dannyglopez, on Flickr

[Dave926]

I know this might seem silly, but check to see that the iat and the clt are within a few degrees of each other before a cold start.

[DannyLo]

Finally got around to cleaning the MAF today. Definitely had visible oil residue on all the plastics. Made a big difference in the way the car drives. A lot less popping and gurgling constantly...and a lot less of the stumbling when i stab the throttle in neutral.

Also got on it once and it seemed to be cleared up of the Lean WOT conditions.

I'm thinking it's time for a better air filter. I've had a Spectre but I think it's gunking up the MAF + causing irregular air reading.

Let's hope that between a clean MAF and a better filter, it stays this way.

[DieGTi]

Good to hear we nailed this one. I cleaned the maf in my c2 car at every oil change and kept the can of CRC spray in the back with the tools to service at all times. Should see big bump in fuel economy as well.

[DannyLo]

Good to hear we nailed this one. I cleaned the maf in my c2 car at every oil change and kept the can of CRC spray in the back with the tools to service at all times. Should see big bump in fuel economy as well.

Yeah, car is night and day with driveability. I did notice in the recent past that $20 wasn't getting me very far, and I was sure it wasn't just the prices Now I know why.

I'm going to keep some MAF cleaner with me too.

Going to change to a better air filter also. I've been reading on the Spectres, and 1; I hear alllll sorts of things on quality. Some good; others terrible. 2; It has this little inverted cone element on the top of the filter, and I have been reading that some MAF car guys, even in some old archived thread on here about VRTs, have reported that it causes shotty MAF readings because of extra turbulent air.

Here's what I mean:



That being said, as extra insurance i'm looking into another filter. I really like the ITG stuff and its obviously of tremendous quality, plus the foam would probably make for straighter flow exit out of the filter and into the inlet pipe because of the foam cells, but I can't justify $100 on a filter....yet.

Comparison of silver Spectre to ITG:



We'll see I guess