87 2.9L Running on 5 Cylinders, but passing comp. test???

[MarkusMcBride]

1987 ranger with 2.9L cologne engine. 135km on truck, must have sat at some point. Truck was running really rough when I got it so I threw new plug, wires, coil, dist cap/rotor. Saw an improvement but when I pull #6 plug wire off, you barely notice any change in running condition - it's still running rough and has no guts going up a hill. It's running on 5 cyl.

Passed comp test by me and then by mechanic. Mech did injector pulse test, no red flags. I have had valve covers off, nothing looks obvious but that doesn't say much. Timing is good, spark is good, injectors seem good.. ideas? worst case - best case? Please and thanks

 

[Big Jim M]

I'd be really looking at the plug wires just to make sure again. Then I'd be thinking injectors. If it is indeed running lean on #6 then that plug should show a lean condition.
Big Jim

 

[Spott]

Just because the injector is getting a good pulse, and even opening, didn't mean it's not fouled. A clogged injector will dribble fuel into the cylinder, instead of spraying a fine mist. The fuel is unlikely to ignite under those conditions.

Verify good bright hot spark, note any unusual spark plug appearance, and then try some fuel injector cleaner and see if that helps.

 

[MarkusMcBride]

The Mechanic said he's thinking heads/valves/valve train related. I just want a second opinion. With the injector pulse test showing no signs of malfunction, It seems as though a valve issue is likely although I am asking for a second opinion. Hopefully someone has experienced something like this before. I should add there is no sludge on oil cap, and no signs of coolant in the oil.

 

[MarkusMcBride]

Thanks Spott, I should have mentioned that I ran 3 tanks of high octane with injector cleaner through it already. Still think it could be the injector? I can change #6 injector pretty easily. I may do that - it could wind up being a very simple fix - before I look into doing the heads. Thanks

 

[ssny1088]

I would double check GOOD spark first. Then look at injector. If it has good comp, then valves should not be leaking/stuck open. If all else checks good, take valve cover off and check valve lift. Just turn by hand. Possibly collapsed lifter, loose,broke rocker(doubtful) or cam wiped out.

 

[MarkusMcBride]

How can I check the valve lift? All of the lifters were turnable but there was only one that was partially collapse and I am pretty sure we cleaned it out (ran a quart of diesel in the engine before my oil change). All other lifters were too stiff to compress. REALLY hoping its not a lobe. How do I check valve/rocker lift?

 

[Milton]

Can you swap an injector and see if the problem follows the injector ?


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[ssny1088]

Turn motor over till they begin to lift and watch how far they move. They sell jigs/dial guages but you should see if one is not opening much. Probally intake(if either) as exhaust not opening would give intake backfire. Know it's a pita but would double check everything before tearing down.

 

[MarkusMcBride]

I think I will swap the injector with another one and see if the problem follows. I'll let you know how that goes. I may pull the valve cover on that side again to visually check the lift as well. (id replace the injector now but ford doesnt carry them anymore so I'd have to wait for shipping) Thanks everyone

 

[Milton]

If the problem stays with cylinder 6, swap the plug wire. If it stays with #6 swap the plug. If it stays with #6, examine/replace the distributor cap (yes I read it's a new one). If it still stays with #6 then it's got to be a mechanical issue with #6.


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[MarkusMcBride]

GREAT NEWS!! Well hats off to you Milton, we pressed on checking the Injectors even though the mechanic did the pulse* test - and when turning the engine over with the fuel rail off, the #6 injector was not firing enough to atomize the fuel (get that nice mist). New injector $87 later (not remanned, new) and she runs near perfect. I am PUMPED! Can't wait to fix other misc item now that the engine is smooth.

 

[Milton]

Glad you fixed it!