need help with troubleshooting misfiring

PaSpic32 · Aug 6, 2015

I bought a '88 ranger with a 2.9l fuel injected engine about 3 years ago. It ran horribly when we got it, it would buck around and acted like it would fall off the mounts. We just started seriously working on it and tweaked the timing to smooth out the engine from rumbling around like it did but it still dies pretty much as soon as you stop giving it gas. We've made sure that the timing wasn't 180* out multiple times, even put new timing gears, chain, and tensioner in it. idles smoothly as long as in has gas. could this be the fuel system at this point. would it be worth purchasing a fuel pressure test kit and spending time cleaning the injectors. Kind of at the end of my rope, any help is appreciated.

enjr44 · Aug 7, 2015

I am a little confused about the "stop giving it gas"; but, if it was the fuel pump it wouldn't run above idle and not at idle, it takes more fuel to run above idle.

If you mean it dies without having the throttle open, it sounds like the IAC valve is not opening to provide the air needed to idle when the throttle body is closed.

On a fuel injected engine fuel flow through the injectors is based on air going through the engine. Air going in is measured and computer adds the correct amount of fuel through the injectors for that amount of air. So when you close the throttle there has to be another way for air to get into the engine. The IAC valve is a computer controlled vent around the throttle body so measured air can get in there. All fuel injected Rangers have one.

Take the IAC off and with its electrical connector still plugged in, turn the key from off to run. Each time you cycle the key the valve should open and close. If not clean it and see if it works. If not it is a bad valve, bad wiring, or bad computer.

I don't remember how to test the voltages. Do a search on this forum because it has been posted several times.......

PaSpic32 · Aug 7, 2015

yah i should have clarified about giving it gas. i meant that it won't idle on its own, i have to keep the throttle open. but i checked the IAC valve and it seemed fine. it runs so bad that i starting to agree that the valves are out of adjustment. is there anything different i should know about adjusting these since i believe they are hydrolic lifters.

enjr44 · Aug 10, 2015

Well, you do it by the book. Should be able to find the info here (search box) or on google.
It isn't hard just involved.

But, because it runs, before I did any of that, I would do a compression test. A lot easier and will tell you if any of the valves are open when they should be closed. Or do a pressure test, harder; but, if a valve is open you will hear it (as well as see it on the tester).

need help with troubleshooting misfiring

PaSpic32

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enjr44

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PaSpic32

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enjr44

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