4runner cold throttle/idle issues - Toyota Nation Forum : Toyota Car and Truck Forums

denverunner · 12-06-2011, 08:51 PM

okay so Ive searched the threads and i have found people with similar problems to mine, but not exact. I have a 1990 4runner 3.0 4WD. the engine has recently been rebuilt, and water pump/spark plugs/wires/cap&rotor/timing belt are all new.
ISSUE #1: When I start it cold, for the first 10 minutes or so(until its warm) i seem to have a dead spot in my throttle. I can get around just barely hitting the throttle but if i dive it 1/4 down or more it completely cuts out for about a second or two then revs up like it should.

Issue#2: my idle is a bit funny..when i start it it stays around 1500RPM, which im told is normal, then it heads down to about 800 once she warms up. However, when i drive it on the highway and im slowing down it idles at about 1500, then goes back down to 1000 or so only if i almost try to stall it, otherwise itll stay around 1500. it also fluctuates between 900-1000 RPMs when idling warm. yeah, it confuses me too

I would really appreciate any suggestions or advice you could give me about this as soon as possible. my wife and I are taking the runner on a 3,000 mile road trip next thursday, and I would like to have it running right before we leave. It runs GREAT when warm, just slightly surging idle, it just hates being cold lol...Thanks so much, God bless

jetwhine · 12-07-2011, 11:24 AM

denverunner,

The things I would do first, would be to take the MAF off and clean it with the spray can MAF cleaner, then I would remove the throttle body and give it a good cleaning and then check the TPS idle stop make and brake continuity check. That is very important as this makes them run crazy if not set at the feeler gauge settings.

denverunner · 12-07-2011, 01:59 PM

thanks so much! I'll try to see if I can get on that asap. I already ran some cleaner through the maf, but I may try swapping with my uncles 4runner to see if it helps anything. I'll let you know what I find out!

denverunner · 12-08-2011, 06:43 PM

ok so I cleaned the MAF,made sure the resistance levels were ok, and I also made sure the TPS is within spec...so what could it be? im stumped

jetwhine · 12-08-2011, 11:26 PM

denverunner,

You might want to (or maybe not) take your throttle body off and give it a good cleaning also. All the ports etc. I would do it off of the rig. You can get better results if it were off. Also have you checked all the vacuum lines for integrity? No cracks, non disconnected, etc.

denverunner · 12-10-2011, 12:31 AM

already took the tb off and cleaned it while i adjusted the tps, and I checked the vacuum lines and replaced a few questionable ones=no luck. At this point im thinking it may have something to do with my cold start injector or time switch, maybe squirting too much fuel? or not any fuel? I'm going to get the voltimeter and check resistance values, etc tomorrow...maybe ill find something

jetwhine · 12-10-2011, 11:35 PM

denverunner,

I did not suspect the cold start system at first as you have mentioned that your idle increases to 1500 rpm and then returns to idle. But............ if the timer is failing and sending a signal to give injection to the injector when it should not, then it could most likely be the timer not functioning properly. It could also be the ECT sensor that is causing the problem. As that sensor sends a signal to the ECM to turn on the cold start circuit due to temp. and then it is up to the timer to control the amount of time that the circuit will work and the ECT sensor to tell the ECM when the temp it hot enough and the cold start system is no longer needed.