Tristan Fox

Hi guys,

i recently brought my first rx8 and yesterday it ran perfectly. Lovely power all the way through the revs, today however I was out for a country drive and felt a slight drop in pulling power and a definite plateau from 6k onwards.

im failing to redline from 2nd gear upwards and is a struggle to get 75mph out of it.

Today was the first day i pre mixed the fuel and I used castrol 2 stroke oil. Only about 100-150ml to a full tank so I'd like to think that wouldn't have made such a difference.

Yesterday it was driven 100 miles home plus a car meet in the evening. To say the least I was using its full potential and getting used to the car.

A few searches have pointed me in the in the direction of a CAT issue or a injection/ignition problem over a loss in compression. The car starts fine, only one more turn is audibly different in the start up.

A few few people noticed some small amount of smoke and pops at high end gear changes. It recently had a compression test back end of last year and was all in the 6.6-7.1 range so no signs of an issue.

What do you guys suggest to try trouble shoot the issue before I take it to get compression checked next weekend. Is there anything I should do and can do this week to try improve the issue. Should I be concidering it could be a ecu problem and is limiting its self?

jcbrx8

Tristan,

- Do you have any CELs? If so, read their codes.
- Potentially a stuck APV valve comes to mind. The 8 uses a series of valves which open & close at specific rpms to optimize intake tract volume . The APV opens at 6k rpm to support high end performance. If it's stuck & failing to open...your engine w/b suffocating at high rpms.

Admittedly, you'll need to t-shoot...start w/your CELs..., but I'd suspect your cat or APV.

Give this a read re: the APV.

https://www.rx8club.com/series-i-tro...stions-212307/

Tristan Fox

I didn't have any cels, it's tried bypassing the oem sensor and that didn't change anything. I only have a cel for that as a result.

What would the solution be for the values should that be the issue?

CaymanRotary

6.6-7 is pretty low. Could grenade at any time. If you suspect engine damage it's worth doing another test just to make sure it isnt that. Checking your Cat is imperative at this point as well.

Tristan Fox

I didn't suspect any engine damage just yet as is seems to be holding revs and idle very well, not much fluctuation in idle and hasn't cut out before. It's just very very limited and less than half the power it had.

the CAT is the next thing I'm going to check though, tonight I checked the maf and other possibilities. What is it I'm looking for? And how do I go about checking it at home without taking it to a garage? Is it a simple process?

CaymanRotary

The cat you can bolt off the car and look at. Looking for clogging, cracks or general condition of the catalyst.

You could test the engine with a regular compression tester but it wont be 100% accurate. Better to use a rotary compression tester if possible. Here's a vid that explains how to do the test with a regular compression tester:

Tristan Fox

Brilliant, I'll take a look today and get some research in.

Thanks for the clarification, I'll get the CAT off tonight and take a look.

NotAPreppie

Checking the catalyst is the easiest first step. Just lift the car, support on jack stands, remove the front crossbrace, unbolt the cat from the exhaust manifold, tilt it down so you can look inside.

If that looks fine, check your intake valve solenoids mounted on the UIM right up against the firewall. This is less likely, given your symptoms, but still possible and not too terribly difficult. Access is easiest by removing the UIM but I've read people saying they've been able to pull the solenoids without doing so (not sure how unless they have spaghetti noodles for arms).

All three solenoids mounted there are mechanically identical. The only difference is which vacuum hose and wire harness connector they are attached to. One is the SSV, one is the VDI, and one is the air pump. They all mount to the same vacuum accumulator.
SECONDARY SHUTTER VALVE (SSV) SOLENOID VALVE INSPECTION

CaymanRotary

Could check the solenoids but usually if there is a problem with those it throws a code for it. I find it much more likely that the problem lies in the Cat or compression issues. Agreed though, I dunno how people remove those without removing the UIM first. They must enlist their children for some old fashioned child labor.

NotAPreppie

Mine didn't throw a code when one of my solenoids just perpetually opened the vacuum port to the atmo port.