bryan

O.K. this is the deal, I have an 89 4runner with a V6 and manual tranny. This thing has been running like crap. It will start but only idles at about 500 rpm's. Once it warms up it will not idle at all. I can tell it is running rich becouse it is blowing black smoke. I have recently changed the MAF, the new one still checks good. I have replaced the cap, rotor, wirse and, fuel filter. I was getting an EGR code I took it off the engine cleaned it out, now no EGR code, but I am getting a code 42 VSS. I took my gauges out last night and no VSS (that is if I was looking in the right place?). The only other thiing I can think of is I have a large hole in the muffler, could lack of back pressure cause this? One last ? is their any way to troubleshoot this. I am stumped any help would be great. Thanks Bryan

nunsa

Greetings,
As you know "black exhaust" is a cause of ye olde 3.0 running rich, most things that cause this are your AFM as you have mentioned, other things would be your cold start injector/time switch staying on and thus over enriching the engine with too much fuel. Other things would be a restriction in the amount of air coming in to the engine. Don't forget to check your fuel pressure also, if your pressure regulator would go T/U you would get high enough pressure that the engine couldn't take all that fuel being dumped into the cylinders. Other things to check would be your spark, if it is weak or you have one cylinder out..., it won't completely ignite the fuel causing a rich condition. I believe I covered most of it, I'm sure some others will chime in.
Did you try turning you idle up? There's a seal on the idle adj. screw and sometimes it goes bad and will cause air to bypass or turn freely, something to check.
Take care and best of luck!

bryan

Thanks for the input, I think the cold start inj. is working fine becouse after it warms up a bit it runs worse. I forgot to mention I have checked the spark on all cylinders and have also done a compersion ck. The compersion was good not great though. How due you ck fuel pressure? I will try the idle screw the next time I get to mess with it. Thanks again Bryan

colsoncj

When the vehicle is cold, it can handle the extra fuel delivered by the cold start injector due to the increased density of the cold air. However when it warms up the air becomes less dense and given the same amount of fuel supply would cause a richer mixture. Hence the cold start injector still could be your culprit. Besides that I don't have any ideas off the top of my head except for the fuel pressure being too high. Have you checked the timing?

bryan

Yes I have checked the timing it's set at 10 degrees BTC. It is running rich on start up also would that rule out the cold start inj.? Just a thought I have been beating my head against the wall for a week, I'll try anything at this point. Thanks

drkgypsy

Well according the most holy of "repair" bibles...the FSM says that code 42, the vehicle speed sensor signal trouble area's are:#1. open or short in vehicle speed sensor circuit,#2.vehicle speed sensor (itself), #3.ECU. This is outta the FSM for the '91 3.0. 100% same engine, or damn near.

Here's 1 outta deep left field...I doubt this would have anything to do with it, but.....could whom-ever did a "tune up" accidently put in a colder set of plugs? If they are the right plugs, are they gapped right? The gap for the 3vz-e is 0.08mm (0.031 in). Did you check the EFI electronic circuit w/ your volt meter.....

wrenchmonster

How about an intake leak causing the o2s to see lean and therefore command ECM to dump fuel to compensate? How about the o2s itself? Do you have a good toggle? Plugged catalytic converter? Just brainstorming here.

-Wrenchmonster

bryan

I figured it out it was the MAF stuck colsed. It read good on the ohm meter, but the butterfly was stuck closed. Removed and replaced it and all works good!

hamstrungtaco

nice doesnt it feel great when stuff works