1991 V6 3VZE misfire issue
 

Hey Guys,

I'm new to the forum here, and I do see a lot of topics on misfires, but it looks like people have had a lot of solutions to this sort of problem.

About the truck-


I picked up the truck with 93000 miles a little over a month ago. The truck ran perfect when I purchased it. The problem started when I started getting trouble code 25. The idle would be up and down- sometimes the truck running great, and other times bogging out of first and second- but still driving up to max speed.

This lasted 2 weeks until about a week ago, when it just all of a sudden dropped drastically. Idle is now at 500 when warm, loss of power, bogs out of nearly every gear and reaches a max speed of 60 mph. It feels like the truck is running on 4 cylinders.

What I have done-

Spark plugs and wires, distributor cap and rotor. Replaced O2 sensor and Max Air Flow sensor. No difference in treating the misfire. Still getting code 25. It is consistent through all the gears, and the idle is steady at 500. I'm assuming the next option is moving into the fuel injectors.

I'm not the most mechanically inclined- I can twist a wrench and I have worked on motorcycles a bit, but not much. I can't afford to pay a mechanic so I'm stuck doing the work no matter what.

Any suggestions and help is much appreciated.

Thanks for your time and I hope with your help I can knock this out and get back on the road- commuting on an XR400 on the highway at 5am to work is not fun.

Quote from YotaTech member rajin from post below.

https://www.yotatech.com/forums/f116...5-26-a-114272/

"code 25 ..Air/fuel ratio lean malfunction..... probable cause..injector circuit, oxygrn sensor or circuit, ECM, fuel line pressure(injector blockage or leakage) ,air temp. sensor or circuit, air leak, air flow meter, air intake system, ignition system"

I would refer to the information I have posted above from a members previous post and continue to work your way down. Unfortunately, this kind of issue is a pain as it can be 1 or more things causing this issue.

Thanks for your reply. Pulled the wires, looks like 1, 3, and 4, are making spark, but when pulled, make no difference in performance. Looks like these ones are misfiring. I'm under the impression it is the Fuel Injectors for these cylinders. The truck was sitting for a few years and its possible since i purchased it with my daily driving that they got clogged from whatever gunk has accumulated.

I'll look for a write-up on how to do these fuel injectors, and will come back if I have any trouble.

On a side note- Is it worth giving Seafoam a shot? What is the most proper method of using this stuff? Gas tank or through a vaccuum hose? It seems theres a lot of skepticism regarding this stuff, but could save time and money if it actually worked

Seafoam is cheap and works ok, but I would recommend using the techron additive which you can can from Oreily's or Autozone as well.

Also did you wire your distributor correctly? Your engine will miss fire if its wired incorrectly.

The dist is wired correctly. In order to do the Seafoam / "techron additive" but I would need to mainline that in through the front? or is it effective by adding to the gas tank?

Thanks

I would just pour 1 of the 2 in the gas tank. I would not recommend putting them in the intake hoses.

Well guys, I don't know what to do.

I sent the injectors out to witch hunter, and had them cleaned. Had the dealer put the intake back on and it ran like a top.

Few days go by and the truck is misfiring a slight bit so I stop driving it. Pulled the tank, and the tank is rusty and the fuel pump is corroded. Replaced the filter and lines and tank. Drove the truck 100 miles and I was back to where I started- 3 cylinders completely misfiring.

Thought it might be the catalytic converter- it was the original. Cut it out and straight piped- still no difference.

I have two days until I leave for a trip cross country to Florida hauling a trailer and motorcycle.

Dealer thinks the injectors my need cleaned again, which would put me out another couplr hundred dollars.

I have to be out of my place in 2 days.