advice? ping/thermostat

[secretz]

Hi. I just inherited/bought a 98 cobra from my friend. The car runs great, but tends to ping every once in a while in hotter weather (and less in cooler weather...and it's not all the time either) or due to the quality of gas. My friend suggested that I get a new thermostat for it to see if it makes any difference. The car has a diablo chip but the timing has been retarded a bit due to the pinging.

I've been looking through thermostat threads and haven't found anything that'd answer my question. The car doesn't overheat at all and the vaccum lines seem to work fine. I've looked through the haynes manual and saw:

opening temp: 188-195 deg.
fully open temp: 212 deg.

Should I stick with an OEM thermostat or will the cooler aftermarket thermostats work better? (and which one? 140, 160, or 180)

If you can help, thanks.

- amber

 

[Toasty]

It sure sounds like a lean condition. Your best bet is to see if there are any error codes stored in the computer and then go from there.

If you are putting premium in it and do not have an air leaks in the intake after the maf, I would tend to think its the Diablo 'chip' thats causing your pinging.

 

[secretz]

The pinging was before being chipped.

Here's some more additional info about the car:
(As quoted from a stangnet post from TheCrazy1)

I have a stock 98 Cobra, just Flowmasters and K&N. I took it in for a chip and custom dyno tuning a few weeks ago only to find that it's pinging too much to be tuned. I was disappointed to find it's only putting down 248RWHP. It's pinged for a long time and the only thing that seems to help is to put a couple gallons of 100 octane unleaded in the tank. I've replaced the fuel pump (it actually died awhile back), the coil packs, plug wires, spark plugs, MAF sensor and all the fuel injectors. The guy doing the tune told me there's no trouble codes, O2 sensors are working fine and suggested that I replace the whole exhaust system. Occasionally, I get a sulphuric smell when I drive it hard as if the cats are overworked. Periodically, I get a rough idle as if the engine is straining to run, but after driving it, this clears right up. I've even replaced vacuum hoses and checked for leaks and everything looks good. So my question is.... do you guys think the exhaust system could be causing this ping, and is there anything else you can think of to check?

 

[Red98CobraStang]

so the stock H is still on the car? throw on a non catted pipe and see if the car runs any different.

If you get a rotten egg smell, the cats are dead/plugged up.

 

[RED 97 COBRA]

Check the egr valve and it's vacuum lines. The black cap on the egr vacuum control solenoid pops off and there is a foam sponge filter inside. This filter gets plugged with dirt and prevents the valve from equlizing internaly so it can close when not in use. This can cause the egr valve to hang open slightly. This will allow exhaust gas to recirculate into the engine when it is not supose to and build carbon deposits on the valve further agrivation the situation. This can can a lean misfire condition. Since egr is inert the O2 sensors can't read the displaced oxygen condition and the computer reacts by leaning out the a/f ratio.

Just something else that can be a problem area on these engines.

David

 

[9746Cobra]

An engine decarb (Sea foam) can help get rid of carbon build up in the combustion chambers. The layer of combustion increases compression, until it's too high.

You may have to do it twice. This ended the pinging on my '97 and I'm going to do it to the '96 but it rarely does it.

9746C