I have a 1993 Loyale 2wd and it's doing some crazy idling. It "surges" at 1000 rpm it goes from 950 to 1050 up & down up & down. My check engine light has been on for awhile I thought it was because of the bad diode pattern in my alternator. I haven't checked my codes yet but plan on doing it sometime this weekend. Any help would be great.

Generally, an idle that goes up and down is an indication of a vacuum leak. Check all rubber hoses and also the vacuum for the power brakes.

Check your error codes first thing.. we can go from there..

No fuel system is given, so I will assume it's SPFI

 

1) idle problems in many cases can be attributed to the IAC (Idle Air Control) valve.

Mounted on the front of the throttle body, this valve controls idle speed via a measure vacuum leak.

 

It is controlled by the ECU and has a shuttle that can get gummed up and cause these symptoms - it can be removed and cleaned with fuel injection cleaner.

 

2) There is a chance that the FI coolant temp sensor is also causing this problem.

 

3) diode problems in the alternator will not cause an engine check light, nor will a dirty IAC.

 

If I had to guess, when you get around to checking the error codes you will find a code 34, EGR solenoid.

 

If you care to check your codes here is a very excellent post on the topic

 

Hope this helps

 

ECU Error codes and the EA82 SPFI

I'm thinking that #1 and #2 will not give a ECU error code, right?

Sir Bard you are correct

 

Unless the wiring to them or the unit itself develops an "open" for some reason.

 

The ECU is looking for continuity (resistance) within a relatively wide range.

It only trips the CEL when it sees a resistance way out of spec.

 

Infinity (i.e. an open circuit) is out of range.

 

 

Hope Korrupt66 answers.

O.K. I checked the codes and I got 24 & 34. I've changed the egr valve once already. Oh well I'll do it again. As for the air control valve I have no idea where it is and my Haynes is no help. Thanks for your feedback so far guys.:-p

Changing the EGR valve will not help with a code 34, as the code indicates a failure if the EGR solenoid . Follow the vacuum line from the EGR and it will lead you to the solenoid.

 

Unfortunately, I can't give you any advice on the Air control.. Been a while since I messed with an SPFI car, and every time I try to explain anything about the IAC, I screw it up and Skip has to swoop down and rescue the hapless victim from my advice..

 

So, heres to hoping Skip will come swooping down..