MARK3 ,sometimes hard to start, idle rpm not stable.
 

My car is hard to start sometimes, and idle speed is not stable, sometimes 500-1000rpm sometimes 1000-1300rpm, I just rebuild the engine, so does the wrong timing set could cause this problem?

Sure, timing is a possibility, so is a vacuum leak, bad ISCV or a damaged air flow meter.

Have you checked for any diagnostic codes? http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx

Thanks for your help!! I just checked my DTC, there is no code,( the engine light just keep quick blink so no code ) It is pretty easy to start my car this time but idle speed still not stable, change from 1000 to 1350 rpm pretty fast. I will check the timing tommorw.

Another question, how to set the timing on this Supra 1987 7mge MT? What I should check before I start set the timing?

http://www.toyota-supra.info/forums/...-new-post.html

Also check for vacuum leaks and splits in the intake hoses. Make sure the AFM is firmly plugged in. Make sure the ISCV is firmly plugged in; Listen for 4 clicks under the hood when the car is turned off, that's the ISCV resetting... if it doesn't it may be damaged or stuck.

Also make sure the timing belt doesn't have slack in it... do NOT over tighten the tensioner pulley though! It WILL cause warping of the #1 cylinder.

I checked everything today, everything is pretty good except timing, timing is 4 degree BTDC at 760 rpm and where I live is 7200 feet high so I think I should adjust the timing more advance(13 degree BTDC).

I forgot to say everytime my car warmed up(about 4 min), everything just runs fun but if you drive it you will feel not enough power. Before the car warm up, I can smell the engine was running pretty rich.

You MUST insert a jumper across T(E)1 and E1 in the diagnostic box when setting/checking the timing. Additionally, NO CODES can be present, the throttle MUST be fully closed and the A/C MUST be off... and the engine needs to be at normal operating temp. The timing is supposed to be at 10 degrees BTDC, the ECU will advance it further based on sensor feed back, it's not an old Chevy, advancing it further yourself will actually do NOTHING.

Here's the process from the Toyota Service and Repair Manual:
http://www.cygnusx1.net/Supra/Librar...aspx?S=IG&P=20

And yes, from a cold start the car will usually be quite rich... it runs richer on purpose. ;)

I adjust the timing today, but I adjust the timing at 860 rpm not 700 rpm( it is the lowest rpm) , the engine runs really good now ,idle rpm stable at 1000 rpm, but I get a new DTC.....Which is #51( Switch Signal, No "IDL" signal, "NSW" signal or "A/C" signal to ECU, during diagnosis check )

No code Yesterday but #51 DTC show up today when I start the car. You said no code can be present when adjust the timing so I don't know if is OK or I should find out what is the problem and how can I do the Diagnosis.

Oh yeah other than this, my car's gas pedal has about half inch free play and not very sensitive, always take about half second to raise the RPM after I depress the gas pedal, is this normal?

Code 51 will occur if:

the throttle is pressed while in diagnostic mode or there is a problem with the IDL switch in the TPS

the A/C is on while in diagnostic mode

an automatic vehicle is not in Park or Neutral or the Neutral Start Switch is defective


All of these will cause idle problems and timing can not be set with any of these problems present.


EDIT: check the throttle cable for excessive play... AFTER you fix the other problems. The TSRM covers adjusting it.

Quality！ So how can I check the "idl" at TPS and what is the full name of "IDL"?? I remember there are 4 terminal at the sensor.

http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=101

IDL is the full name, it's not an acronym. It's a signal line which the ECU monitors so it knows if the throttle is truly closed as opposed to relying solely on the TPS voltage.