need some freakin vaccum diagrams, and some tips on a vg30

[eds13]

picked up a 86 nissan hardbody 4x4 (d21) with a VG30 in it.

whenever i mash the pedel it bogs, it almost feels like an exhuast brake, just kills the whole motor. and through the rest of the rpm range theres like no power at all.

so what is it? vaccum? timing? just a pos vg30? lol

help me out people!

[S14-NEO]

could be a multitude of things..timing, fuel pump, MAF sensor...at idle i presume its fine but whenever you put a load on the engine its when the problem occurs. i would lean towards a fuel issue, poss fuel pump lose of pressure when a demand is put on it, MAS sensor if its not able to add fuel to the increased engine load...just a start.

[eds13]

heres the thing, its almost like its getting choked out... not a lack of fuel. and it does idle fine.

[philipa_240sx]

Last time this happened on my '87 Pathfinder (VG30i), it was due to faulty ignition wires and distributor cap. It worsened in damp weather. As soon as the engine was put under any sort of load, it would immediately bog as the spark would arc across the distributor cap instead of the plug. The disributor cap, rotor and plug wires should be replaced as a complete set. They seemed to last about 100,000km (62,000mi). I must have went through 3 or 4 sets.

The other issue which caused a similar problem was a faulty TPS (throttle position sensor). The TPS is comprised of potentiometer and an idle switch. Over time the circuit board cracks causing faulty readings to be sent to the ECU. This affects fuel enrichment and ignition timing during throttle application. Usually it starts to show up as a miss while cruising, but it gets progressively worse.

If the ignition is OK, then start checking the fuel system. Replace the fuel filter if it hasn't been done for awile. Then check the fuel pump pressure and delivery rate.

If the fuel system is OK, then things get a bit more involved. It could be an electrical issue, faulty sensor, bad ground, etc.

I would start searching for a factory service manual. Search for 'nissan truck service manual' on Ebay. It's your best bet as they are no longer in print. A manual from 1986-1989 should work as the models are very similar with the same VG30i motor.

[FoxFire]

i had a simliar issue

check for water in the maf plug

also advance your timing a lil bit