Idling Problems on start up
 

Hey everyone. I just bought a 2007 rx8 gt a couple days ago an have already had an accident. The hose going to the heater core just randomly popped off and antifreeze sprayed everywhere. I'd got that problem fixed, but now I have a new problem. Ever since that happened, my car starts stalling on warm up..? It usually only does this on cold starts, but I was just curious to how this happened. The person I bought it from said it was in perfect condition, and it ran great until that hose came off. (I'm assuming someone didnt clamp it on there very good) So I was just wanting some input on what you guys think the problem could be. Coils, plugs, battery, a sensor? Thank you.

Oh and the car only has 52,000 miles on it.

That heater core hose popping off probably lead to an overheating engine. Even if briefly. Overheating is deadly to this engine, and only sheer luck will let you overheat it without causing damage. The common point of failure on an overheating engine is the coolant seals.

When one or more coolant seals fail, you will typically get a slow coolant drain into the engine. When the engine sits off for a period of time though, this coolant collects in the housing and makes cold starts much harder. When the engine is running, the coolant will be contaminating everything, messing with the combustion, fouling plugs, etc...

Start looking for an engine replacement. It will run for now, but coolant drain into the engine is terminal as the coolant will start eating away at everything inside it. Expect an inability to start it up within the next 10,000-20,000 miles, and you will be eating through spark plugs like crazy until it's fixed, leading to additional problems (like cat failure).


Edit:
Coolant seal failure is pretty much the only failure method which results in a hard cold start with a fine hot start. Technically, leaky injectors could be looked at too, but they are far less common than coolant seal failures, and considering you just had a cooling system failure immediately preceding these symptoms, coolant seal failure makes sense.

Thanks RIWWP. That makes sense. I still don't see how I could have overheated it. I noticed the coolant temperature light come on, so I immediately pulled off to the side if the road. The temperature gauge was normal. So, I had a friend take me I get some antifreeze, and after we added that, everything was fine and the coolant light turned off. Except, for the check engine light. I wonder if the antifreeze could have messed up a sensor? I'm no expert by any means.

The coolant light is a low level light, not a temp light.

The CEL could be anything, did you get the code?


Keep in mind that you don't need a general overheating event, where the entire cooling system reaches critical temps. You only need the engine around one of the coolant seals to get too hot and it's done. Not having any coolant will mean you will reach that incredibly quickly, even if the coolant temp sensor never recorded critical temps. Having the coolant dumping from the engine while the engine is running is always really bad news. It doesn't take long to push the coolant out at idle, and since the water pump is directly related to RPM, if you were driving it could have pushed the coolant out even faster than that. With the heater core hose disconnected, the pressure differential is also suddenly seeing an outlet by pushing coolant out of the hose, rather than through the engine, so the coolant that is still in the engine is going to have a huge loss in circulation. So by the time you got it to the side of the road and shut off, the engine block could have been sitting there with basically no coolant in it, and it's going to be blazing hot with no where for the heat to go (since there isn't any coolant circulating or possibly not even any just sitting in the block).

The coolant seals can indeed fail incredibly quickly given the circumstances you noted.

I got the codes. They are p0506 (idle air control system problem), p0302 (cylinder 2 misfire), and p0300 (random misfire).

Yeah, those could easily help support it. Pull your plugs and look for coolant fouled plugs. That would easily cause the misfires.

The P0506 has among it's possible causes a coolant temp sensor failure and compression loss. Both are entirely possible as a result of what happened.

Alright. I'll check my plugs right now. And, you're sayin I might need a new coolant temperature sensor?

Possibly, yes. Possibly no. There isn't enough information yet to suggest that it did indeed fail. The P0506 has the coolant temp sensor as only one of it's failure possibilities. It's among a much bigger list though:

Okay, I'll check the spark plugs, and I'll try to figure out the p0506. Thank you so much!

I think the spark plugs did the trick. I took it to a dealership to have them inspect for leaks. There are none. The p0506 code is gone. However, there are still the misfires (p0300 & p0302). I don't think this has anything to do with the coolant. I might look into the coils now.

Just bought a 2004 rx8 and it lags when step on the gas any solution would really appreciate it

Lots of possible things it could be.

I suggest you create your own thread in this subforum and provide as much detail as possible.

Heater core
 

Hey man Im having the same issue. How did you fix your Heater Core leak? *2004 93K In my case my passenger side floor is flooded with antifreeze. And Car won't start....... Long Story short:

While driving, temp needle starts to pass its normal estate, I, then immediately pulled over, waited bout 1 hour for it to cool down since I was only about 1 mile from home. while that 1 mile drive to get home, temp needle stays normal. As soon as i parked it starts going up quick, So I quickly turned the car off. I noticed coolant got splashed through the overflow hose. Next morning I checked coolant reserve, it's empty! so I fill it up, it only took 1/2 gallon. Try to turn the car on, NOTHING! I checked every hose i could possibly think of under the hood fro any leaks. it all seems to be in place and clean. While troubleshooting I noticed that my passenger floor mat is soaked wet. I removed it, there is a puddle of coolant on the floor mat.

Plugs, Wires, Coils were all changed at 72K. so they are only 20k old. I still plan on replacing them with NGK's that I had just bought 2 weeks prior to all this mess.

I just want to get a general idea on how to fix the heater core leak.

My problem was what RIWWP stated earlier. My heater core hose didn't have a leak. It completely came off, which fried my coolant seals. I had to get a whole new engine replacement. Thank goodness for the warranty........... If your car isn't holding antifreeze like it's supposed to, there is your problem for it not wanting to start up. I'd see what a moderator has to say.

Sounds like new engine time, housing are probably warped, compression is lost, coolant seals are fried.

I knew that is the worse possible thing that could be. Im hoping it s just flooded, then do a compression test. If the engine is bad then i may just trade it for an R3. But I really hope it s just a flooded engine.