I have an 86 with 70K miles and it failed the emmissions test for high CO. I initially thought it was just the thermostat because the temp normally goes up to about 145. The idle goes up and down, more when it is cold, but does it sometimes warmed up too, so I am not sure if it is just a temp related problem. I put my Scanner on today and nothign seems to be out of the ordinary, no codes. Of course, it isn't like I really know what to look for, any ideas??

 

Temps as low as 145 are only good for racing. I'd SAY you have a thermostat issue. Do you even HAVE one? These cars were designed to run at 200+, and largely for emission reasons. At 145, there is a chance, you're not even going into closed loop. Slap a 195* stat in there and change the oil. If it still doesn't pass we can start dealing with it from there. Good luck, and...

RACE ON!!!

 

145 ... sounds like no thermostat or stuck wide open... :iagree:

 

Thanks guys, I will change or install a thermostat and report back.

 

Be careful when loosening those t-stat housing bolts. Take it slowly if they're tough to loosen. I snapped one of mine. Looked like there was something on the threads.

Bill

 

Hi.
I had a lot of idle trouble. There are some elements that influence on it.

Check the PCV valve if it is okand the that the crank house ventilation is connected to the throttlebody (check the hoses/tubes from the valvecover )

Then check for false air. That is relative easy to do. take a start gas aerosol bottle or a propane bottle and spray the gas around the intake manifold where the runners are and if you get an increase in the rpm then you have a leak and that must!!be fixed. If not the computer will not be able to interprete the signals correctly and wants to compensate. There will be too much air on the O2 sensor and the MAF do not send signals of the correct amount of air as there are false air coming in after the MAF and the you have the cycling.

The EGR will also be a parameter that can give influence on the idle. Check that. The EGR valve can have a bad diafragm . If you have a vacuum pump with a gauge you can check that the valve will hold the vacuum according to the book (think it was about 20 secs). If it cannot then you have to change the valve. There can also be dirt so that the EGR does not cloes properly. Check also the EGR solenoid for proper functioning.

I had to change the EGR vale due to leakage in the diafragm and i had also false air between the runners and the manifold. It was the runners (largetube) that were not properly machined so the gaskets did not make a proper seal. I had to machine them for an even surface. Then everything became good.