Hey guys! First time posting. This is my second fox body. This one is a dual ignition 2.3 4cyl. It wasn't wanting to warm up so I thought te thermostat was stuck open so I bought a new one to put in. I went to put it in and found out there was no thermostat in it. I put it in it warms up but only up to the first dash mark which I think is roughly 160 degrees. I drive around Portland a lot so it does get a little warmer and when it does it runs really rough. It starts jerking and acting like it's missing. Which is weird because the dual ignition should make up for it shouldn't it? But it only does that when it's warmer than 150 or so. They guy before me put what he called Nissan high flow exhaust. It's really loud and annoying and I'm wondering if that could be the culprit. I do have a check engine light so I plugged in the computer and I got codes 629 which is converter clutch solenoid failure or fault. Which makes no sense because it's a manual. And I got code 566 which is 3-4 shift solenoid circuit failure. I have a feeling it's air or some of the smog and emissions stuff because that stuff always causes problems. Thank you guys so much for all the help. It's greatly appreciated.

 

Welcome to the forum!!! Ill try to help out. When my stang was reading half the temp lol I changed out the temp sender and it ran great afterwards

 

It's located on the backside of the engine. You have to get the car in the air to see it. It's about $7-8. Also I should have one wire plugged into it

 

Ok. So it's just the temp sender is kicking on the cooling system too soon. Do you know anything about that sputter?