shakes when stopped and in drive. check engine light came on P1506 and p1504?

1998 MAZDA 626
157,000 MILES • 4 CYL • FWD • AUTOMATIC
Avatar
AIDEN522
  • MEMBER
  • 3 POSTS
I have a 98 mazda 626 2.0L DOHC 4 cylinder that shakes when stopped and in drive.No check engine light came on. A scanner came up with this.

P1506
Idle air control system overspeed error
failed IAC valve

p1504
electrical load failure
cause:IAC circuit open or short circuit condition
failed IAC solenoid

I replaced the IAC valve as well as replaced all the spark plugs,wires and tested the ignition coil.IT still shakes bad when i turn the A/C on.
this is starting to drive me a little crazy.

I also have another question.I'm replacing the throttle positioning sensor.Does it have to be a particular kind or can i put a universal one on?what kind should i get for this car?

PLEASE HELP
Feb 11, 2011 at 4:30 AM
Advertisement
Avatar
FIXITMR
  • CERTIFIED EXPERT
  • 9,990 POSTS
did you clear codes and re test for codes again after repair?
Feb 11, 2011 at 5:59 AM
Avatar
AIDEN522
  • MEMBER
  • 3 POSTS
Yes,and its still doing the same thing.I replaced the TPS today with no change.What would be the next thing that I should check?
Feb 13, 2011 at 12:23 AM
Advertisement
Avatar
FIXITMR
  • CERTIFIED EXPERT
  • 9,990 POSTS
It sounds like you might have low compression on one or more cylinders. This guide can help.

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run down this guide and report back.

Feb 13, 2011 at 1:25 AM
Avatar
AIDEN522
  • MEMBER
  • 3 POSTS
Good call, #2 was at 80 psi, time for a valve job.
Feb 13, 2011 at 2:17 PM