Engine stumbles and bogs
 

I have an 89 Pickup with the 3vze engine and I’ve been chasing my problem for a while now. I’ll start from the beginning and hopefully someone could give me some insight. When you try to start it it takes about 5 or more seconds to start and sometimes longer it used to fire right up 2 years ago and after it’s started the RPM’s bounce up and down pretty erratically and a lot of times will stall and quit. It revs ok but as soon as you try to take off and you put a load on the engine it acts like you just put the choke on and tried to go. While it’s doing this it will quickly run ok for half and second and then back to barely running which means it quickly takes off and then back to barely running and every time it does that it throws you back and forth. One time it did this for about 5 minutes straight and I couldn’t go anywhere in a parking lot it just wouldn’t go. After it gets warmed up it doesn’t do it near as bad as your driving but it still does it. Periodically it will miss out and shake the entire truck very hard. It will do this at low RPM’s and consistently at 3200RPM on the dot it almost will not go over 3200 because it just misses out and the RPM’s fall about 200RPM every time it does it. Now when you put the truck in neutral or just push the clutch in theirs a good chance the engine will stall and die. I honestly don’t remember it backfiring at all it used too but I haven’t noticed it doing that for a long time. Now the things I have done are NEW vacuum lines and new timing belt. I just replaced all the vaccum lines in hopes that that would be the problem but it did nothing. I was thinking it could be the valves needing adjusting but I don’t hear any clacking but if they’re too tight I don’t think they would clack. Any thoughts?

Ran diagnostics
 

I got a code that says the Air Flow Meter and the 02 Sensor are bad so I’ll work on this and I’ll get back.

Replaced the Mass air flow meter and it did nothing
 

I replaced the Mass Air Flow Meter with a new one and it didn’t improve anything in fact it gave the code back that the mass air flow signal is bad so I replaced almost every single vaccum line with a new one and I know my 02 sensor is most likely not working because the exhaust melted the wires but I cut where it was melted and repaired each wire. Thats the other code it’s displaying I mean if it’s giving out false readings I’m sure that could be a big problem with fuel trim. Also I’m trying to find a diagram on how to test the Mass Air Flow Meters connector to ensure it’s doing what it’s supposed to in terms of voltage and such.

Crappy Running Issues
 

Make sure your ground wires and connections are in good shape first. I chased a similar problem on a fresh engine rebuild and it was a new NTK O2 sensor that would cause the engine to run like crap after it warmed up and went into closed loop mode. Denso only for replacement parts. The transition from cold to warmed up can help if the symptom occurs when at one or the other of the two engine temperature conditions. If it is not transitional with temperature then perhaps the TPS is wonky or the throttle body housing needs to be removed and purged of the carbon fouling about the throttle plate and various ports? Like your thermo stat there is a wax filled actuator valve in the throttle body housing which creates a controlled vacuum leak and allows the engine to have an increased idle speed when it is warming up. That may be clogged up with carbon/oil residue and not letting the engine start easily and since it seems to by dying at idle perhaps even the idle adjustment port and or screw seat is plugged with crap. Cheak the steel tubes that are part of the vacuum line circuits for internal corrosion induced blockage as well. ECM needs knock sensor, TPS, AFM, and crank trigger signals from the distributor as well as good grounding in the wiring to be happy!

Best of luck in discovering the culprit!...

Problem Solved
 

Alright so I finally got my Factory Service Manuals and they are amazing. My problem was the coil in the distributor was bad so book said replace distributor and she runs perfect.