Today is the day!

[Chanman1029]

I highly suspected leaking valve stems seals causing a drop in power at 7200 rpm for me, I went full send on a bottom and top end rebuild. Should be doing the first start in a couple weeks

[jet_dogg]

stash had mentioned to double check o2 locations as well, though the two shortest are pre-cat and the two longest are post-cat

[LSBNick]

In your old thread you said the same thing about getting the compression checked, then you posted,



Now you're again talking about getting the compression checked? I think it's pointless trying to diag your issue when we don't know exactly what maintenance with what parts has been done to the car.

A valid point, I was told “compression was great”, however didn’t take the time yo do my due diligence and actually verify. Just took the shops word at face value (dumb mistake on my end).

I work what seems to be 24/7 but will finally have some time on Tuesday to go through my records and see what exactly was done with what parts and when. Once I have everything compiled I’ll post here with as much detailed information as I can gather.

[jet_dogg]

In your old thread you said the same thing about getting the compression checked, then you posted,

Figured I’d give a quick update here.

Car has great compression, and have since replaced my fuel filter, converted my EKP to a traditional fuel pump relay, and had my injectors cleaned/rebuilt as needed.

Retuned by HTE, car is now putting down 318 whp and 231 wtq.

Definitely an improvement, and glad Hassan was able to make his magic happen.

Currently trying to find a way into a SS V1 set up, and will retune the car again with that new setup.

As for now, car is running like a dream, completely linear power band, and is a blast to drive. Thanks for all those who gave their input and experiences!

Now you're again talking about getting the compression checked? I think it's pointless trying to diag your issue when we don't know exactly what maintenance with what parts has been done to the car.

[heinzboehmer]

There's very few potential sources of vacuum leaks on this engine because of the ITBs and they're all around the throttle bodies. If you had the stock intake and MAF there could also be unmetered air leaks to worry about, as that would alter the mixture. However, since you've got a CSL airbox, all you have to worry about is vacuum leaks.

These are all the ones I can think of:

• Thottle body to head gaskets
• Idle ports o rings
• ICV to throttle body piping
• Brake booster vacuum line
• Fuel pressure regulator vacuum line
• The idle air rail itself (pinhole somewhere or something)
• Emissions solenoid thing, but you'll only have that if your car is an 05 or 06

[ZiMMie]

Flash it back to stock and diagnose/fix your issue.

[LSBNick]

Side update:

the buyer of my old ARH setup just dynod his car. US 6mt Vert with roughly 90k miles. Ended up putting down 312whp and about 244 torque.

[LSBNick]

Quick update for those who are semi-following. Car threw bank1 and bank 2 lean codes today on the way to our local CCA meet. Given the fact that this is after the tune, I’m leaning towards a vacuum leak (hopefully) being the main source of my problems.

I still plan on doing a compression test, and depending on results, a full leak down test, but wanted to ask to forum if anyone has experienced something similar to my situation, and what the most common vacuum leak on S54s are.

Thanks for any input/help in advance!

[jet_dogg]

Everything on this list has been addressed except the TPS. I’ll have to go through my records and receipts to verify when and what brand of new parts were installed. Most, if not all, were purchased through FCP euro

Keep us posted on compression and leak down. You need to get to the bottom of this.

[LSBNick]

I bet it sounded good on the dyno, though!

Yeah at least the sound is nice lol

[LSBNick]

I would go back to basics first, start small and move on to large as well as the comp and leak down.

If you haven't already or it's time I would r&r:
coils/plugs
cps/tps/o2s
check fp/clean injectors/ replace fuel filter
vanos test

Everything on this list has been addressed except the TPS. I’ll have to go through my records and receipts to verify when and what brand of new parts were installed. Most, if not all, were purchased through FCP euro

[jbfrancis3]

I bet it sounded good on the dyno, though!

[jet_dogg]

I would go back to basics first, start small and move on to large as well as the comp and leak down.

If you haven't already or it's time I would r&r:
coils/plugs
cps/tps/o2s
check fp/clean injectors/ replace fuel filter
vanos test

[LSBNick]

As of now the plan is to do a compression and full leak down test and go from there. Could be a ton of different things, but I feel this is the best place to start.

[LSBNick]

It's also super jagged. Something is up..

And more jagged than before, with the same smoothing factor.

Funny enough the same dip is present in the original graph. I think it’s time for a top end rebuild.