92 Rodeo hesitation and stumbling on acceleration

hesitation
rodeo

#1


This problem has been hanging around like a poor relative since December and we just can’t seem to get close to the solution.



The truck runs fine when cold, but once it warms up to operating temperature I get random hesitation and stumbling,especially when accelerating. Sometimes when idling at a stop light, the idle speed will start flucuating and it will stall.



I’ve put in a few rounds of dry gas and fuel system cleaner replaced the fuel filter, 02 sensor, coolant temp sensor, checked the throttle position sensor, check the idle air control. I don’t have a problem starting, so I’m not inclined to suspect the fuel pump. The truck has been inspected and passed a PA emissions test. Exhaust is solid, and it seems to be delivering the amount of pressure out the tailpipe. Spark plugs have been checked and re-gapped.



I’m not displaying any engine codes, and the check engine light is not on. In fact, with all the other work I’ve done, it runs quite well when it’s not screwing up.



I’m running out of things to check. Last time I worked on it with my Dad (he’s a mechanic), we couldn’t get it to fail in the garage. I can only seem to get the problem to express on the road.



My Hayne’s manual has basically run out of things to tell me to test.



Any ideas will be aprecitaed.



92 Isuzu Rodeo, auto, 3.1L, auto, 172K.


#2

The ignition coil can cause these problems of misfire.


#3

Interesting. Especially as the truck won’t start at all right now. battery reads 12 volts at the terminals, but the voltmeter reads much less.


#4

The Book has three resistance tests for the ignition coil. It passed all three.


#5

The voltmeter reads much less where? Do you mean the voltage is low at the igniton coil? If you look at the wiring diagram, it should show you that the ignition coil gets voltage from the ignition switch through fuse #9. If you turn the ignition key to START, and don’t get 12 volts at the coil, the ignition switch has high reistance in that circuit. You could run a jumper wire directly to the ignition coil and see if the engine, then, runs. If it does, consider changing the ignition switch (NOT, the ignition lock).


#6

battery reads 12 volts at the terminals, but the voltmeter reads much less.

???


#7

The instrument in the dash.


#8

The instrument reading on the dash. We had a real wicked cold snap yesterday and today. It may just be a case of a frozen gas line. There wasn’t much fuel in the tank.

There were three tests on the coil according to the book. It passed all three. But I’ll look at the voltage at the coil.


#9

Look at the wiring diagram. The 20A Ign coil fuse is hot in Start and On, isn’t it? Turn the ignition key ON and check for 12 volts at the ign coil fuse. Turn the ignition key to START and check the ign coil fuse for 12 volts. If there isn’t power then, the ignition switch is bad.
Make sure the sensors on the intake tube and throttle body are connected.
Use a carb and throttle body cleaner in the throttle body bore and throttle plate. Use the cleaner spray generously on the idle air control valve pintle and passage.