89 4runner...running problems

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

When you checked the AFM, did you check the voltage smoothly changed throughout the motion of the flapper? It basically provides a voltage that is proportional to the amount the flapper is opened up by the air going into the engine. If it has a dead spot the ECM may think the engine is still at idle.

Now, for that signal. AFM/Vacuum. What happens if the vacuum is at zero or goes to zero when you apply throttle? What could not properly be switched on/off, or switch on/off that is required for smooth operation?
 
Thanks bogo, I double checked my AFM. And I think I've got a bad one. It doesn't smoothly supply the voltage back to the ecu. According to the trouble shooting in the FSM, the AFM is bad. I hope to find one tomorrow and try it after work.
 
Well, New AFM later, and no more code 31. Still won't run well. Now won't idle as smooth as it used to before the new AFM. Will idle until warm and once it is warm it surges. I took off the AAC and cleaned it and it still does it. Any ideas?
 
When you say surge, does it jump up in idle speed and stay, or is it going up and down. Is the up/down random or regular in it's cycle?

For surging under drivability/surging the Fuel pressure regulator is listed as a first possibility, then spark plug, distributer, injectors, then finally ECM.

If it is just a high idle, they list allot of possibilities. Take a look at the engine troubleshooting section in the FSM.
 
It jumps up and down and up and down. It is regular. I looked at it when I had my timing light out and noticed that the timing was jumping when the idle was jumping. I will look at that section.
 
Hey, does anyone know if the Coolant Temp Sensor might cause my symptoms? or What about the Cold Start Valve? for instance, what if the Cold Start valve works when it's cold, but then doesn't stop working when it is warm?

Any ideas?
 
Well, gonna pick up 4runner from the shop today. Still no worky. The mechanic was stumped. Anyone know if a Catalytic Conv. would cause the symptoms I am having?
 
a clogged cat wont cause it.
have your mechanic do a smoke test on the intake.
i suspect either a leak in the air tube from the AFM to the T body
or a fault with the circuit opening relay, or further the fuel pump relay.

if not there then a good chance of valve timing problem like the timing is off. do a vacuum test
 
Thanks Wristy. I will look into those. The mechanic has thrown in the towel, so the ball is back in my court. Will work on it.
 
Double checked valve timing, and I'm on there. Double checked compression...175, 173, 175, 175. I don't know what it's suppose to be, but I thought that looked good. I did find a possible leak in the intake gasket. Fixed that, but it still doesn't want to be throttled.
 
How do I do a vacuum test? What should it be at? I don't know how to calibrate the TPS, either. I will search the FSM on these suggestions and figure out how to do them. If I unplug the AFM it automatically dies. Which it should, right? Because of the Fuel Pump circuit being controlled from the AFM?
 
Ok. I'll try and call you. I have school tonight from 6-9 pm MST. It may be tomorrow afternoon. Thanks for your offer.
 
Thanks Wristy. You are the MAN. The TPS was the culprit of all of this. Now, I noticed the oil is milky, so I messed up my Head gasket or the Timing Cover somewhere is leaking coolant into my oil. BLAH. I thought I was on the Road.:crybaby::mad::bang:
 
You must log in or register to reply here.

Share this page

Back
Top Bottom