banzairx

I recently picked up an 04 6-port car with 92k on it which had a "hot start" problem. That turned out to be a bad fuel pump. Now I'm onto another issue with the car which is high RPM lack of power. Another symptom is when on the highway going up hill it will lack power. I'll floor it and you count 5 and then it will spring to full power. It was also exhibiting power loss at lower RPM's randomly before I started trying to fix the problem too.

Here is what I have done so far to try and resolve the issues-
Pulled SSV valve and cleaned it. It was VERY dirty. Moved easily with my finger before and after.
VDI valve checked and moves easily
Replaced all the solenoid valves under the intake.
Replaced fuel pump
New spark plugs and wires.
Replaced coils with known good set from another 8 I have
Checked Cat.- It was empty
Replaced muffler thinking pieces of the cat maybe lodged in it
There is no check engine light or stored codes

So after all that the inconsistent lower rpm power is gone but it still behaves like the SSV is sticking- Power loss starts at 6,500-7,000 rpm with popcorn type noise. Any idea what to look into next?

9krpmrx8

iTrader: (46)

Any flashing CEL or other codes? How do you know the used coils were good, did you test them? Have you checked vacuum at warm idle?

banzairx

No CEL, No codes.

Coils came out of my daily driver which was running great on them. I only pulled them from that car to do a preemptive upgrade to the LS coils.

Have not checked vacuum at idle. Should be easy enough to pull with the OBD2 logger.

banzairx

16.6-17“ vacuum @ 800rpm according to the obd2 reader.

One other interesting note is long term fuel trim is +22%.

lOOkatme

check and clean fuel injectors.

9krpmrx8

iTrader: (46)

Okay so you have not checked the coils then. You know what they say when you assume right?

As for the +22% LTFT, I just fixed (after he took it to the dealer and Midas) an RX-8 on Sunday that had that the same LTFT stuck at max and a lean code. It had a vacuum leak (jet air hose was disconnected on the LIM) and the intake was full of oil and the MAF was coated in oil due to the car having a quart too much oil in it. The vacuum leak was fixed and the intake and maf were cleaned and I extracted a quart of oil and the car is running fine.

banzairx

As far as the coils go it ran exactly the same with the original coils as the ones I swapped in.

Don't think it's the injectors since the AFR is actually a little rich when floored but not making power. When power kicks in it leans slightly.

I cleaned the MAF sas I had an over rich condition on my other car caused by that so it was one of my go to's.

Only thing I can think of right now is a vacuum leak. I'll have to start spraying some brake clean around and see what happens.

banzairx

One other note is I reset the fuel trims and within 10-15 miles it was right back up to +22%.

9krpmrx8

iTrader: (46)

Ummm, don't use brake cleaner. And your fuel trims are maxed out, your troubleshooting methods are flawed, you need to actually test things.

banzairx

Why wouldn't I use brake clean? Been using it for literally decades to troubleshoot vacuum leaks.

What should I be testing? What methods are flawed?

CelestialGryphon

iTrader: (1)

I... I mean, my knowledge is limited as far as brake clean goes, but it's pretty good at degreasing, which means it's the last thing I want to get anywhere near the inside of my rotary which has a staple diet of grease and fuel. I think that's sort of what 9k's getting at here. Also, for cleaning the maf or sensitive electronics you'd be using MAF cleaner, something that's still a detergent but more gentle.

supermiatavaper

From what I've read and researched, if it's not the SSV, and the ignition system is fresh (coils, plugs, etc), I would check the cat and make sure it's not clogged up. Many have reported high RPM power loss with clogged cats.

banzairx

MAF was cleaned with MAF cleaner. Been reading up on high LTFT's and a bad MAF is one of the culprits. I'll look at it's output when I drive the car again.

Not to worried about the brake clean doing any engine harm. Only a very small amount will get into the engine. Gasoline is also a very good solvent.

supermiata- the cat is empty. Not sure what happened to it. It was like that when I got it. I also replaced the muffler(got a new take off from craigslist for next to nothing) being worried the cat bits may have been lodged in the original.

banzairx

Tried like crazy to find a vacuum leak today with zero luck. Only progress was on the MAF, it is reading low. I have a new one on the way.

archwisp

iTrader: (1)

I had these exact symptoms with my Racing Beat intake. It would all be snug when working in it but once the car got warmed up, the filter element would go rubbery and slip out if the ring holding it to the airbox and cause a vacuum leak.

But yeah, all seemed fine until it would slip loose and all of s sudden during acceleration it felt like someone threw an anchor on the car. Let off and it would close up enough to drive "normal".

banzairx

Changed out the MAF after checking the output and was getting ~4.2g/s @ idle, a little low. Swapped in the one from my daily driver and g/s go up to 5.2/5.3. I didn't drive it on that one, just hot idle. New sensor reads the same as the one from my DD. Now it has an idle issue. Fuel trims have maxed out. Even after a trim reset and 50+ miles of driving it will barely idle. O-ring on the MAF is good and sealed.

Overall after thinking this through I don't have a vacuum leak unless it opens up at high rpm. Unlikely but I'm going to check my intake accordian for cracks. Idle was rock solid and the power loss is at high rpm. The vacuum leak necessary to cause high rpm power loss would be HUGE. It would have easily been found.

I also had some one to help me other day and they revved the car while I watched the intake valves. The SSV & VDI open as they should. No way to tell what the 6 port actuators are doing.

This thing has a gremlin somewhere and it won't beat me!

banzairx

Not sure if anyone is paying attention to this thread anymore but the new O2 sensor has shed some light. The car is going very rich top end. AFR's are in the mid 11's. The loss in high rpm power is being caused by an overly rich mixture.

banzairx

made some real progress today. Problem is both intake valves and it's really sneaky. The vacuum chamber has a leak that only opens when the engine is hot. The valves are only being opened partially by the loss in vacuum.

banzairx

So that was definitely the problem. Replaced the vacuum chamber/oil fill assembly with a new/used unit and she's running 100% again.