OK this only happens under the following conditions:
- Engine is at normal operating temperature
- Car is in Drive or Reverse


This only started happening when the weather got cold out. In Neutral or Park the car is fine. It's only when there's a load on the engine.


I thought it was vacuum lines and found a vacuum leak so I fixed my lines. No check engine light is on. The RPM's go up and down when I'm at idle in drive at a red light. If anyone has some insight on what to check please let me know thanks!

 

Check for codes. U can still have codes w/o the CEL illuminated. Always use diagnostics before buying parts.

 

test the engine temp sensor at the front of the water pump. check iac (intake air control) sensor to see if its carbon'd up.

 

Thanks guys. IAC is 1 year old. I don't mind spending the $30 for a new temp sensor since I didn't replace it when I replaced the water pump. I did seafoam my intake. I'll check the IAC..... just a pain to take it out lol.

 

you can test it with a ohm meter without taking it out. http://shbox.com/1/4th_gen_tech2.html#ect

 

better test fuel pressure too. does it sould like a missing cylinder? maybe check all your plug wires and make sure one is not lose or damaged.