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Tim West
Tim West, ASE Certified Technician
Category: Saturn
Satisfied Customers: 4638
Experience:  ASE Certified Service Manager 10 years.
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1999 Saturn: sedan..cuts..The TPS and IAC motor was replaced and it

Customer Question

i have a 1999 Saturn sedan with a 1.9L that is idling rough when put in gear. It idles rough and cuts off after a few seconds. The TPS and IAC motor was replaced and it still does the same thing. What are my other options. Could it be a problem with compression or valves, rockers etc? Please get back to me. My email [email protected] or respond on this site. Thank you
Submitted: 7 years ago.
Category: Saturn
Expert:  Tim West replied 7 years ago.
Thanks for visiting Just answer,
Do you have a check engine light on?
Customer: replied 7 years ago.
Expert:  Tim West replied 7 years ago.
Okay, the next move you should make is get the code scanned. Autozone will do this free. The problem you are having could be a misfire, vacuum leak or something not so serious. Since a rough idle is a pretty vague problem with many possibilities it's the best choice to illuminate any unnecessary diagnostics.
Can you get the codes scanned? As I said Autozone does it free.
Customer: replied 7 years ago.
ok I will get it scanned and get back to you in about 15 minutes
Expert:  Tim West replied 7 years ago.
I will be waiting
Customer: replied 7 years ago.
ok 5 different codes came up but none after cleared. I can hear valves tapping and the codes were as follows: 1: P0304 Cyl 4 Misfire 2: P0300 Random cyl misfire 3: P0122 Throttle Position Sensor Circuit Low input 4: P0706 Transmission Range Sensor Circuit Performance 5: P0304 Cyl 4 Misfire.

What are my options? or What am i looking at?
Expert:  Tim West replied 7 years ago.
What is the 8th of the vin number?
Customer: replied 7 years ago.
8 is the 8th digit
Expert:  Tim West replied 7 years ago.
Ok if you haven't replaced the plugs recently do so now, click here for info on that. Plugs are cheap and easy on this vehicle.
This might take care of the (p0304, p0302, p0300 codes these are the misfire codes).
Still the p0121 TPS code is a probelm and can cause this issue you are having as well, since you replaced it let's ignore it for now. If you just replaced the IAC.
We can check the wiring if we need. Make sure there is 5v to the sensor.
The p0706 code is for a transmission range sensor. Not sure how it fits in to any of the symptoms. We will look into that in one second. Let's see if the code comes back or not. I would suggest replacing the plugs for right now and checking the wiring at the TPS and let me know.;graphic
Customer: replied 7 years ago.
ok plugs wires and coil packs were replaced 5000 miles ago. ill check the wiring voltage tomorrow. now when i drive for a while the tapping valves stop but the idling or puttering still continues and eventually shuts off. however this only happens when in gear. also i forgot to mention that when on the code reader machine the idle jumps sporatically between 643-809 rpms.

Expert:  Tim West replied 7 years ago.
Well, there is probably a wiring problem with the TPS causing the idle to go crazy. Also, make sure the intake manifold gaskets aren't leaking or other vacuum leak isn't present. A vacuum leak can cause misfire codes. Get some carb cleaner and spray the engine area down and listen for the engine to respond to the external fuel.
You can also try blocking the throttle body and verify the vehicle stalls.
If the engine keeps running with the TBI blocked there is a vacuum leak.
As far as the tapping make sure the engine oil level is OK and the oil is new.
I am not saying the tapping might not be abigger issue, but for now lets see if we can't at least get the vehicle running better. Ler me know how it goes.
Customer: replied 7 years ago.
I checked the wiring on the sensors. There is 5.06v at the TPS sensor and 11.96v going to the IAC
Expert:  Tim West replied 7 years ago.
Drive the vehicle around the block a couple times, and see if the engine light comes back on. If it does, have the codes scanned again to see what codes are setting immediately. Can you do this?
Customer: replied 7 years ago.
Yeah i Can do that. Ill let you know what its done
Expert:  Tim West replied 7 years ago.
Thanks, XXXXX XXXXX want to make sure we aren't looking at the TPS and there is nothing wrong with it, since you did replace it.