Mysterious 97 Ranger Issue... in limerick form


#1

Some requisite background on the problem:
Back in '09 I picked up a beat-to-hell ranger for $700 on craigslist. 44 miles later I ended up having to rebuild the engine (my first rebuild ever). It all came together except for a few minor things (2 CEL codes: p0135 & p0141) that were there before the rebuild. Almost 1 year after getting it up and running the new problem started.

-Symptoms-
Sudden power loss
Backfiring
The engine sounding ‘bogged’
More backfiring
Rough idling

But they all seem to come and go. Sometimes it will idle fine, others I have to really work to keep things going. The problems with power loss and backfiring (and rough idling) seem to get worse/more common the longer the truck has run. Usually after a backfiring (or five) power returns for a little bit and then bogs out again.

-Things I’ve tried-
-Fuel pressure checks out between 25# and 35#s at idle/coasting, 40#s under WOT (Video of test run: http://www.youtube.com/watch?v=uzxkCnUuy_4)
-No gas smell in pressure regulator’s vacuum line (line is not plugged either).
-I have not been able to locate any vacuum leaks (aerosol spray test).
-I have installed a new fuel filter.
-Plug wires are routed correct.
-Plugs and wires are new, gapped correctly.
-MAF has been cleaned recently.
-IAC valve has been cleaned several times.
-Mechanical timing has been checked and re-checked
-Swapped coilpacks to test if I had a bad one

So here is my limerickal next guess:
A problem most vexing,
No new codes have been logged;
My next shot in the dark is,
That the cat may be clogged.

My thoughts are that the cat is partially clogged and, once it heats up, it swells closed and begins to build up exhaust pressure. The backfirings temporarily knock the clogs free and return the exhaust to a free-flowing state. Any thoughts?

And a parting shot in the form of another limerick:
This truck’s an enigma
What’s even left now to break?
I think it may be better,
at the bottom of a lake.


#2

I fail to find any limericks in your post. A limerick has 5 lines, 2 long that rhyme, two short that rhyme with each other and one more long that rhymes with the first two lines. But they are poems, just not limericks.

You say that you have checked the mechanical timing several times. Does that include the valve timing, that is the timing belt/chain?

The codes you have point to the O2 sensor heating circuit. It could be a bad connection or broken wire, but is more likely to be in the O2 sensor. That would throw off the fuel injection when the engine is cold.

You fuel pressure seems a bit low to me also, but I don’t have the specs for your vehicle. You will need to look up the specs.


#3

Bump

Does anyone have any guess what the problem may be? Is there an easy way to test if the cat is bad?


#4

The owner of a beat up Ford Ranger
Has problems that couldn’t be stranger.
But when he gets some suggestions,
He answers with questions;
I guess he’s not a mind changer.


#5

That’s a limerick. Sierra Hotel wentwest.


#6

I agree there’s a good chance you just need a new 02 sensor. Check out eBay you can probably buy a new 02 sensor there for about $20. instead of paying $60-$80 most auto parts stores charge.


#7

Keith:
Thanks for the reply, I think I must have bumped at about the same time you posted, because I didn’t see your post :slight_smile:

I have replaced both O2 sensors (twice) and I have run a new wire from PCM pinout through the entire heating circuit, and back to the return pinout. The code is still there. That said, the code was on when I bought the truck and then for a year after the rebuild. I really don’t think it is the issue here.

Fuel pressure is spot on per the manual.

As for timing, I have not checked the valve timing beyond what I’ve done when I reset the timing belt (cam end). However, if the valves were out of time wouldn’t the problem be persistent rather than erratic?

Thanks again, I hope my mechanicing is better than my poetics,
-Kyle


#8

Try this. Remove the distributor cap and rotor. Turn or bump the engine until you have a vane lined up with the reluctor (ignitor). Now if you have a brass feeler gauge, this would be best but a steel one will still work. Slip the 0.010" blade between the vane and the reluctor. It should just fit. Now push on the shaft away from the reluctor and see if the gap grows. The change in the gap will be slight so you have to have the feeler gauge or you won’t see it.

If you can make the gap grow to 0.017" or more, your shaft bushing is worn out. That will cause the problems listed above. Do this with the engine hot as that is when the gap will be at its worse.


#9

It is a '97 OBDII Lima, so it’s distributerless. This engine has only got about 130K on the head and a freshly (10k miles ago) rebuilt bottom end, do you think the cam bushings could have worn out so quickly?


#10

I did not know they went distributorless in 97, I thought that didn’t come until later. Cam bushings should not cause this problem.

As for checking the cat, do you have a warmup cat (aka pre-cat) built into the exhaust manifold? If so, drop the exhaust pipe and try to look through the honeycomb with a small flashlight and an inspection mirror or stick a long this screwdriver up through the honeycomb. I have seen the tops of the honeycomb on these melt and form a barrier.

Another possibility could be the crank angle sensor, but that should give you a code. Another possibility is bad coil packs, but again you should get a code P030x with x identifying the cylinder(s) with the bad coil. Since you have plug wires, I’m guessing that you have a lost spark system where one coil fires two plugs at once so you should get a code for both cylinders if the coil is bad or a code P0300.