Engine runs great except with engine cover in place
 

Guys,

I have a very interesting problem with my brothers 05 RX8. The care has no power, stalls and floods out when the engine cover is in place, but when the engine cover is removed, it runs great. What could be causing this. I think it might have to do with heat. The engine seams to be much hotter with the cover in place.

Thanks

Are you SURE that is the only variable changing?

Cover on or off, there isn't any impact on the engine itself. The only thing that could possibly make a difference is an extremely neglected cooling system could be struggling, and the slight amount of heat trapping is enough to make it overheat. But that wouldn't give the problems you list (overheating even once can be game-over for our engines).

The only other thing that I can think of as an issue is if the battery cover gets pressure at the wrong point and is causing a battery issue with a loose negative cable, causing grounding problems. This could cause ignition issues (low power), stalling, and flooding.

I suspect there is a different variable though...

this should be good. I got nutin

Thanks so much for your quick response. He has been having this problem of it running like crap for 2 years. Some days are worse than others. We were trying to figure out if it could be the spark plugs and took the wires loose and made sure we had a good connection. Upon starting it up, it cranked immediately. Normally it has to turn over like 6 seconds to crank. Then we took it for a drive. Wow, It ran like it did when he got it. We were thinking we just had a bad plug wire connection. Then he drove it like three more times. We were thinking we finally fixed it. Then as he was leaving to go home, i realized we had failed to install the cover. He came back and installed the cover. Then as he took off again the car started running absolutely horrible again. He then stopped the car and took the cover off. Just took the car for a 45 minute drive. Ran like a top. I will check bad connections tomorrow when he comes over, but I think it has something to do with heat.

In the two years that he's owned it has he ever changed the plugs and coils?

just posted in another thread, have you ever replaced your coils, wires, or plugs. if not, i would do them as it likely needs it desperately.

I don.t think the coils have been replaced. The plugs and wires were replaced at or around the time that all this started. He just replaced the catalytic converter about two months ago. That improved the conditions, but until he drove it today, it has not run this good in two years. Car is starting 2 secs now. He just changed the oil, and filters like two weeks ago. Car has been service relatively good, but not perfect.

Coils failing leads to failed cat. ALLLLL the time.

His coils are shot. Replace those and then test it out again. (please don't just got to the dealer and get raped with their prices)

Is there a way to check the coils before replacing them? It runs so good right now. I have always been told a coil either works or doesn't work. They are very expensive. I have some money to help him get it fixed, but I would hate to buy 4 coils only to find out this does not fix it.

Yes. Buy a $12-$15 coil tester at the local auto-parts store (looks like a spark plug with a clip on the side), disconnect a plug wire at the plug end, plug it onto the tester, clip the tester to something metal nearby, and have someone crank the engine (let it start if it wants to. letting it idle at the same speed for each helps to gauge the difference). It should be a strong and steady spark, in color, duration, and frequency. Check each plug wire end this way. If you find one that seems noticeably off (either no spark, color change, unsteady, unstable, etc...) then swap that plug wire with a plug wire that you got a good result from (to rule out the wire).


The thing about coils is, having even 1 fail can lead to plug failure for both plugs on that rotor due to fouling. The excess fuel will accelerate cat failure. Cat failure starts causing further issues like O2 sensor failure, localized heating in the engine that overstresses seals and can warp the housing, and at worse starts a fire. At best, it's just another $1,300 cat...

When 1 coil fails, the rest aren't all that far behind. Replacing the coils ($30 each) is CHEAP preventative maintenance.

Don't let him skimp.

The 8 costs money to maintain, and will murder your bank account EVEN MORE for not paying attention and neglecting it.

Instinctively I would have to go with guidance by RIWWP and Charles for two reasons:

1) Putting an engine cover back on and having almost instantaneous issues is unlikely to be heat related. Even a rotary takes a little while to heat saturate the motor to the point where problems will arise.
2) RIWWP and Charles are both knowledgeable members of this community.

Hence, I would lean in the direction they are indictaing when they advise that installing the cover may be triggering some other issue besides heat saturation. The cover when installed applying pressure to a questionnable battery connection, other electrical connection, or a cracked/loose vacuum line or hose are all reasonable possibilities behind the issue you are describing.

Guys,

Thanks for all the great hints. We are still trying to work out the exact problem or a small variety of problems that add up the the end result. But I will tell you what we have learned so far.

1. Put the cover back on again and started to run like crap
2. Took the cover off, removed the battery cover, moved the negative cable to the side so that it could not hit the engine cover, then replaced the engine cover. Engine ran great.
3. Took the cover off, with the negative batter cable moved to the side, put the battery cable back over the battery and installed the engine cover. Engine running great.

Clearly have established and issue with the negative cable. We have not figured out what, but running great. I will continue along this track until if figure out what is wrong with the negative cable. Three wires coming off the negative cable one goes into connector. Could just be the connector. Ground connections look tight, and no corrosion at the locations.

We have notice one other thing now that it running so good. I think a previous post might help with this one as well, but I am interested to hear your thoughts anyway. When the car is driving and comes to a complete stop, with the brakes depressed the car will shake quite a bit for about 3 seconds and then even out. Or if you let off the brakes it will work good as well. Do you have any thoughts about this?

Thanks again for your suggestions. Cant believe he drove this thing around in as bad a condition as it was for two years because of a bad ground. But he is no where near a mechanic. He is the type that would sell the car, but could not afford too. Now he's a RX8 fan again.