Muxumus

Hello Yotatechers

I would first like to thank all of you for the amazing amount of information (have been using this site to fix up my just aquired 1990 4 runner with over 300,000 miles). I have an issue which seems to have happenend to alot of people but the solutions either are hard to come by or very varried by nature so im hoping that one of you can shed some light on this issue.

It's a 1990 v6 4Runner with an auto tranny. The problem is a weird idle that sometimes leads to stall.

Its was throwing 3 codes;

• 21- Which is o2 sensor (changed which solved a problem with loss of power when cold, thank you Yotatech.)
• 51 -switch signal park neutral position, not in P or neutral (no idea though it might have something to do with the fact that i can move the shifter without pressing the break so something is def not right there)
• 52 - knock sensor (replaced with new oem knock and new wire, this fixed the power loss and the running so rich i reeked of fuel everytime i drove it but the weird part it sill throws this code every now and then after driving for a while but does not come with the previous power loss or rich smelling exhaust. Will clear code and see if it persist as this is the last fix i did

I have changed;

• Throttle Body with TPS
• Changed the MAF
• Cleaned the Injectors
• Changed fuel pump.
• Changed radiator for new aftermarket 3 lane one
• Change coolant temp sensor

Aditional info for Diagnosis

It basically starts fine, can ride around just fine with her but if she warms up and i turn it back on it starts surging from 300 to like 800 until it stalls out. This does not happen all the time and if i rev it for a while (5 min around) or drive around it seems to stable out at 500 rpm. Since its kinda random its hard to peg down because sometimes she just works fine.

I have read such problems as;
- Sounds like the Idle Air Control valve needs to be cleaned or replaced. (will try this today)
- Something EGR related.

Thank you in advance for any and all help

Saturn

Make sure your Throttle Position Sensor is adjusted properly, there's instructions for how to do that around here somewhere. Check your base timing, and ajust your idle speed the the screw in the throttle body. I, like you, have a 300K+ 90 4runner and went through all this, get a haynes manual, worth their weight in gold for procedures for this stuff. Mine runs like a dream now.