Miss when warmed up.

[Freb_mc]

Sorry, I hate to start multiple threads but this one is puzzling me. I have searched and searched, with no solid answer. The problem is most noticeable when warmed up, at idle. Not so much when on the throttle. And lately when its warmer weather its harder to start. Cranks a bit longer. 3.0 5spd 93 4runner. The miss is mostly harmless until I shut it off. Then once restarted it won't idle. Runs rough then low idle til it dies. If I give it gas it will smooth out and run till you let off. Sometimes dying at stop lights. but from a cold start it never acts up.? Cant tell if its ignition or fuel related. Drive too and from work without noticing anything. But if I stop for groceries or gas it will drive me nuts!

 

[77'911]

I would start with basics:
1) check the battery and charging system
2) fuel pressure test (rest and running)
3) ohm out o2 sensor
4) check for vac leaks (secondary crankcase, fuel injector o-ring, etc)
5) replace pvc
6) clean out throttle body and replace the fuel filter/plugs to give you the best basis to work off from (detonation and metering wise).
7) make sure the t-stat is not sticking open
It does not act up when cold, because it is probably running under the cold circuit.
regards

 

[Freb_mc]

I would start with basics:
1) check the battery and charging system
2) fuel pressure test (rest and running)
3) ohm out o2 sensor
4) check for vac leaks (secondary crankcase, fuel injector o-ring, etc)
5) replace pvc
6) clean out throttle body and replace the fuel filter/plugs to give you the best basis to work off from (detonation and metering wise).
7) make sure the t-stat is not sticking open
It does not act up when cold, because it is probably running under the cold circuit.
regards

1) charging system is good, battery is old and a bit weak, I just got an optima for it. Planned to upgrade the battery cables to at least 4 gauge as well
2) what pressure should I be running? I'll check it this evening
3) what are the specs for the o2 sensor? I'll check it. (I need to get a shop manual)
4) best way to test? Spray some wd40 around or what?
5) got a new one waiting to be put in
6) gonna seafoam it, of have new plugs and wires (ngk) and bosch fuel filter
7) this is new to me, could the temp sensor effect this as well? My temp gauge never comes up really.

Thanks for the response you gave me a great place to start!

 

[77'911]

I'm away from my factory 4runner manual set but I'll take a look for the specs. If the o2 sensor has close to, or more then 90k, replace ( Denso works well). When I replaced ours, it smoothed out the idle and improved the avg mpg by 2-3mpg.
If your temp gauge never goes up, sounds like the t-stat has failed open (not uncommon), or it's a sender. I would replace the t-stat right off. As these trucks age, it is not a bad idea to replace the coolant temp sender. The problem here, is the intake needs to come off to replace it. I need to do ours. I'd skip the seafoam and run a couple of bottles of techron concentrate through it after you get the hot run circuit handled. You might consider using a Japan made fuel filter, the filter elements are better quality and seem to work better with the system.
What is your definition of "good" for the charging system? It's worth doing a "load, no load test" to see where your at with the alt.
regards

 

[Freb_mc]

I tested with a load tester. Did a full charging and starting system test at work. And I'll do some more checking around on it. I picked up a repair manual today well see how detailed it is.

 

[77'911]

Use a voltmeter with the truck running, see what the voltage is, or what the alt is putting out. Then, with the truck running, turn on the high beams and maybe the rear defrost and see what the reading is. This will tell you what is going on with the alt. ; )
regards

 

[Freb_mc]

Well Ill check it again. it tested fine before, but tonight with the high beams on it seemed to pull the idle down. Almost below 500 rpm.