91 V6 running rough

[lt1fire]

My brother in law's 91 V6 is running rough all of a sudden. It's there 3rd vehicle so they don't drive it that much.... I really drive it more often than they do to haul stuff to the dump and as such I keep up on the maintenance on it for them.
All fluids are up to date, new cap, rotor, plugs, wires, fuel filter, air filter all in the last year.
They brought it over last month and said it was running rough and it is..... seems like it has almost no power when driving it and it got worse and slower throughout the week when I was test driving it.

I got busy with work so I couldn't look at it and it's been sitting on my driveway ever since.

anyone ever had this happen before out of the blue??? Going to check the compression on the cylinders today and i'll report back with that.

 

[Tigerstripe40]

there are any number of things that can be wrong here.
How many miles are on the truck?
I suspect its either motor problems or fueling.
A compression test will be useful in helping figure out if the motor is bad. If the compression checks out, the next thing I would look at is the fuel supply. I'd start with replacing the fuel filter and checking fuel pressure at the fuel filter while you're at it.
If the fuel pressure is down, you will need to pull the fuel pump.
If the fuel pressure is good, then I'd look at sending the fuel injectors to a place like WitchHunter who will clean and balance the injectors. This made a big difference.

One other thing it may be is the injector driver in the ECU which means new ECU time.
The 3VZ-E is a batch fire type of injection. It fires 3 injectors at a time.
Hope this helps.

 

[KLF]

I would start by checking the ECU for any codes. You could also start pulling plug wires to see if you can narrow the rough idle down to a particular cylinder.

How many miles? Might be time for the injectors to go have a visit with WitchHunter or Mr Injector.

I wouldn't bother with a compression test, I personally don't think they give very reliable information. Try to do a leak-down test if you can. Not only will it tell you if something is wrong, it will tell you WHERE the problem is.

 

[lt1fire]

Sorry for the vagueness of the first post I put it up fast while I was at work. Got it fixed though, one of the fairly new plug wires had failed and corroded away at one point. Kind of strange by not the frat time I've seen it.

Oh well all fixed and running fine now