SC Running Hot

arbita1 · arbita1's Garage

I've searched, but still need some help:

Last week after starting my car and having a back fire it started to run hot. Typically my car always ran close to the middle of the gauge (in between the 2nd and 3rd marks). Last week and today, it was running just below the 3rd tick mark. I did not notice anything else abnormal. Power, idle, etc all seemed fine.

After driving I felt the oil lines and they were warm, so I'm pretty sure the thermostat is opening.

One thing I did notice, was that one of the heater hoses was not attached at the blower fan. It was just sitting next to the outlet but not attached. Maybe it came off when it back fired last week. When I put my hand next to the hose with the engine running I could feel heat leaking out. Could this be the cause? Or should I be looking elsewhere? One other thing I noticed is that the area where the catalytic converter is was very hot. The body work around the wheel well was extremely hot. I have a premuffler and not a cat by the way. But I have noticed this before and the car has always ran in the middle of the gauge. So maybe that is normal.

Is the heater hose my problem? I guess I'll connect it and go for another drive, but in the mean time I would appreciate any help.

ipacketeer · ipacketeer's Garage

Is it back firing through the intake or exhaust, I will guess it is through the intake since you said it is running hot, engine may have developed a substantial vacuum leak because of that AFR may be too lean causing the back fire.

Gogar · 07-16-2011, 12:01 PM

If your airbox doesn't have a pop-off valve installed, it's possible the backfire could have cracked your airbox, and unmetered air is getting past, making it run lean and hot.

Or maybe it backfired and if you DO have a pop-off valve, make sure it didn't come loose or stay open or something.

arbita1 · arbita1's Garage

Quote:

Originally Posted by ipacketeer

Is it back firing through the intake or exhaust, I will guess it is through the intake since you said it is running hot, engine may have developed a substantial vacuum leak because of that AFR may be too lean causing the back fire.

It only backfired that one time. It was through the intake.

Quote:

Originally Posted by Gogar

If your airbox doesn't have a pop-off valve installed, it's possible the backfire could have cracked your airbox, and unmetered air is getting past, making it run lean and hot.

Or maybe it backfired and if you DO have a pop-off valve, make sure it didn't come loose or stay open or something.

I have a pop-off valve. I'll check to see if it came loose or is stuck open.

arbita1 · arbita1's Garage

The pop-off valve is fine. I reconnected the heater hose. I hope that was the problem.

I've been suspecting an intermittent air leak on this car for a long time.

arbita1 · arbita1's Garage

I went for a drive yesterday and the car is still running hot. The engine temperature was less than last week, so maybe the disconnected heater hose had some effect.

In normal cruising it was running between 110C - 115C (just under the 10:00 position). The weather was in the 90's yesterday though. I confirmed the aux. oil cooler is functioning. The thermostat opened around the 90C mark on the temp gauge.

So maybe it's the internal thermostat? I guess I can try to feel the oil cooler on the engine after it's warm to see if the cooler is warm.

Or maybe a lean condition as indicated above.

ipacketeer · ipacketeer's Garage

Matt,
To verify the AFR is properly adjusted on your car, one of the easiest procedure is to check the Duty Cycle of the FV.
There is alot of information about the Duty Cycle of your engine on this board, if you perform a search you shoul be able to read all about it.

arbita1 · arbita1's Garage

Quote:

Originally Posted by ipacketeer

Matt,
To verify the AFR is properly adjusted on your car, one of the easiest procedure is to check the Duty Cycle of the FV.
There is alot of information about the Duty Cycle of your engine on this board, if you perform a search you shoul be able to read all about it.

Thanks.

I actually have my O2 sensor disconnected right now. So I'm running in open loop.

I have the Gunson gas tester and have set my F/A mixture a few times already. I have to check it again. Last I had it set for around 3.5%. But I have since changed some exhaust components so maybe that is why.