Engine wont idle when it is hot?
 

Okay guys so, I had a busted cat and that threw a CEL. Got a new cat today and started up the car no more CEL and was running perfect. Drove it for a little while and reved the car until 7500 rpms in first and second gear just to make sure the engine stays healthy. After a little while of driving went home parked the car and reved to 3k rpms for 10 seconds like recommended and then turned it off while reving. A little later I was driving and the CEL went on again and when the car got to operating temps the car just refused to idle. It starts and runs just fine when cold but not hot. Could it be bad compression? =/

A little info on the car: 2008 grand touring mt. Car was fully serviced a few months back new oil and spark plugs only running conventional 5w30 and currently has 51k miles. Not sure on the history of the motor forgot to ask the owner so I'm not really sure how many miles the engine has. Let me know if I left anything out guys.

Quick update guys took it into aamco and got a free diagnostic. They said the code was pointing to the first o2 sensor and they said another code was for the neutral safety switch or something. Any idea what the neutral safety switch is about?

The only way to know is to get it tested. There are several other things that it could be as well. Have the coils been replaced? Do you notice any power loss?

No They have not I am hopeing it is just coils have not checked them yet. I guess I will just have to go get it compression tested after checking them. Do you know if it did have low compression what CEL Code it would throw?

There is no CEL for low compression. Get the CEL read then start your searching from there. Telling us there is a CEL light but not telling us which code is being thrown is like telling a doctor it hurts, but then can't tell him where.

If its throwing a CEL, either go to autozone, get the codes and report back here for more help. Or take it to the dealer straight up and while youre there ask for a compression test.

P.S. There is no need to rev your car to 3k for 10 secs every time you shut it off. Maybe if you started the car for 30 secs yes, but if you are driving it there is no need. That "procedure" was only created to prevent flooding.

Ohh okay thanks for that info, I figured you always need to because some people suggested that no matter how far you drive you should do it so I was just being safe. Any way quick update guys took it into aamco and got a free diagnostic. They said the code was pointing to the first o2 sensor and they said another code was for the neutral safety switch or something. Any idea what the neutral safety switch is about?

Also another update the engine stays on when it gets hot now but wont go past 10 mph.

Bump new info guys any help?

When you say it won't go past 10mph, you mean the car literally will barely move? Or do you mean the RPMs won't go past 1000?

I mean that the car literally hardly move. Once I let off the clutch the engine just doesn't take any gas, the idle wont go down as long as I have my foot on the gas pedal but the speed hardly goes up it takes about 2 min of my foot all the way down on the gas just to reach 25 mph. Could this be due to the neutral safety switch?

Hmmm....I'm not familiar with the neutral safety switch but it doesn't sound like it. Seems like if that was the problem, the transmission go into gear or move the car at all. Does it start ok when its hot? Does it backfire or knock or shake etc?

Here is a good thread on the safety switch https://www.rx8club.com/trouble-shoo...switch-133529/

There are others threads on it too if you search a little. A little advice, you can find most of this information by yourself. Use the google search method; it works better than the site search. Example type this in at google "site:rx8club neutral safety switch"

You will generally get more people to help if you show that your are trying to figure this out for yourself and by that I mean spend more than 5 minutes trying to find your answer. Not trying to be rude or sound like an ass but the most knowledgeable people on this forum help those who help themselves.

It starts up just fine when its hot now that I changed the cat. As for shaking sometimes its smooth and sometimes its very shaky its kind of weird it is like the car works fine even with the CEL on sometimes and sometimes it just refuses to work. as for knock or backfire there is none as far as I can tell. The guy at aamco said the engine seems fine and healthy.

If it was truly running perfectly very recently, then I don't think it's compression. That usually gradually becomes evident, it doesn't just....happen. I would look more towards faulty ignition system components like coils or a bad fuel pump. Plugs and wires could also need replacing, bad coils could foul your plugs even if they were replaced recently. Who put the new plugs in and serviced it?

I know what you mean but, I actually did read that thread today after I found out what the problems were. Explains why sometimes when the car gets hot it wont idle just don't really get why the car wont move when it gets hot wondering if it's linked to the neutral switch.

Also another update. I just disconnected the negative battery terminal and when I put it back on the CEL went away and the car drives fine again I think I am going to try new plugs coils and wires and the clutch and neutral switch as well see what happens thanks for all help you guys have provided soo far.

It was at one of those Fire stone complete auto care places

No problem, you should also clean your MAF sensor while your at it, very easy to do and if it is dirty it will also affect your idle.

Hmmm.....Do you know if they put the correct type of plugs in? It doesn't matter so much on regular cars but it's important for rotaries. I bet the wrong type of plugs could cause this prob

Since when this problem is more frequent , and how much time it has passed when you service your car?

If the CEL doesn't come back it could've been a fluke

Okay guys got an update. This weekend I got the car up on a lift to inspect the exhuast make sure it is sitting right and everything was right there ( I changed the cat recently so thought I would start there) before inspecting the spark plugs and coils. Decided to take a look at the neutral safety switch and noticed it was not put on right. Put it back on like it should be and the CEL went away and the car has been running strong all weekend. My best guess is someone at the Firestone place messed with it or something not sure what happen there but my car is all good now =].

Glad to hear it!