crave4speed

iTrader: (1)

Hi everyone, I was directed to this area to post my problems. Please help. I apologise for my lengthy post but I need to describe my problems as best I can. The car is a used 2005 6spd in stock condition. There are 2 main problems. The first problem was there right from the time I bought the car last week and the second problem happened today.

Problem 1: Every time I rev the engine towards the redline, it will pull reasonably well (for a used rx8) up to 7500rpm. At this rpm, the engine will hesistate momentarily and then it will buck/surge all the way to the redline as if a giant turbo kicked in. I'm not complaining about the power that comes after this point. Its the split second hesistation and loss of power that happens before this that I am worried about. My passengers describe the feeling as though I had accidentally clutched in and out at that rpm. It happens consistently every single time in all first 3 gears. I have not tried going faster than redlining in 3rd gear. There are no error codes.

Could this be an actuator issue with the Variable Dynamic Air Intake, Secondary Shutter Valve, Variable Fresh Air Duct or a bad Auxillary Port Valve/APV motor? Or does it sound like an ECU or fuel injector issue?

Problem 2: Brought it to a rotary workshop earlier today and did a compression test. Test was satisfactory showing 6 readings (3 for each rotor) which ranged from 100 PSI to 114 PSI at 250rpm. Mechanic noticed that the air hose which connects between the VFAD solenoid valve's vacuum chamber (located between the airbox and MAF, beside and slightly lower than the air box) and the Extension Manifold (Upper) is lacking a "One-way Check Valve". He cuts the hose and installs the said valve. Later, when I drive the car home, and the engine gets warm, the car seems to lose power. While waiting at the lights, the car's idling becomes very erratic and the car starts vibrating badly and the tacho needle starts moving downwards towards zero. Engine stalls. After restart, the car continues to shake and the CEL light comes on. As I u-turn back to the workshop, the car has no power and feels like its dragging as if one rotor was dead. Mechanic connects a scanner and confirms that front rotor was misfiring. He removes the one way valve that he installed previously and goes for a road test. No more misfiring. Unfortunately, on my way home, the same thing happened and CEL light comes on during the period that the car is sluggish and shaking.

What is causing this sudden misfiring in front rotor after the compression test? Is it possible that spark plug was not screwed on well or plug leads were not connected well? Or does it sound like my coil just suddenly died?

DeViLbOi

iTrader: (1)

1) Found this always to be a good read for new people.

http://www.rotaryeng.net/New-rotary-eng.pdf

7250 is a key point in the RPM cycle. There is a valve that opens up at that range called the VDI...I have no idea how to test it or where it is.

2) Sounds like a loose plug wire that didn't get all the way back on when he did the compression test. *shrug*

crave4speed

iTrader: (1)

Thanks for the article. Yeah, I was told by the garage that its probably the VDI actuators being restricted by carbon build up, hence causing a delay in opening. The other possibilities are Auxilary Port Valve (APV) restricted by carbon and a weak fuel pump that will not show up as an error code.

Update:

Problem 1: Not fixed. Mechanics are too busy to do troubleshooting until next week

Problem 2: Fixed. Turns out that the ignition coils were faulty. A new set was put in. RPM at idle has stabilzed to about 800rpm. CEL light gone and power restored.

Winning 8

try to seafoam it first, before you spend the money taking it apart.
here is the DYI link https://www.rx8club.com/series-i-tech-garage-22/seafoam-newbee-186885/, sorry I don't know where you could get one of those, just google it or something.