Hello everyone, I have a 1993 Ford Ranger XLT with the 2.3 engine. It has 154,000 miles on it. I originally thought the truck was running rich, but this no longer seems to be the case.
I was doing the injector test, and while I was in there I did a compression test, the results came back 100, 145, 150, 150. Cylinder 1(the low compression one) seemed to have some oil in it too.

I got sick, and a few days later, today, I did a wet compression test on cylinder 1. I did it dry first, and it came back as 80. This seemed odd, so I tested the other cylinders and they also all came back 20 psi less than the other day. Its a lot colder today, but I ran the engine for a little bit to get a little heat in it.
After doing the wet test, the compression came back the same, indicating its not rings.
I've read this truck is supposed to be around 165 psi, so all of these numbers are low.
The truck doesn't misfire it seems, it throws no codes, and it runs decent enough for me to drive it. I just bought it, so I have been driving it like this for a month now, and I started to look into a problem when my gas milage was coming back at 17mpg.
It definitely is not making all 100hp, but it runs smooth and has good throttle response. It does like to idle high, putting the clutch in it sometimes stays around 1600 rpms.
On decel, you can hear a noticeable popping, like a crackle tune. I thought this might be unburnt gas from it running rich, but looking at the plugs they look flawless, not of a truck running rich.
The previous owner I believe replaced the timing belt, could the timing be off causing this?
I did the paper over the exhaust test, and the exhaust did not suck the paper back in, indicating good exhaust valves. I really thought it was exhaust valves since it could be leaking the power stroke into the exhaust, making the pops.
As I'm writing this I have a feeling it might just be a timing issue, but I want someone else's more experienced opinion.
Thanks for any replies!!!!

 

1993 2.3l Lima ran 9.2:1 Compression Ratio(CR)

General "rule of thumb" is CR x 18 = expected compression PSI
9.2 x 18 = 165.6psi

In my opinion its best to test compression on cold engine AND with no spark plugs installed in any cylinder, in 2.3l dual plug engine then at least 1 spark plug removed from each cylinder, so no cylinders have compression except the one being tested

Cold engine because metal has not expanded to seal any leaks, the point of compression test is to FIND LEAKS, not get high numbers

Point of compression test is to get numbers using same gauge, battery and at the same outside temp and elevation all at the same time
Then you can compare those numbers

Metal rings against metal cylinder walls and metal valves against metal valve seats are NOT good as air seals, lol
They offer, at best, a temporary restriction to reduce air leaking out
So crank piston speed is a factor in the compression number, so no compression in other cylinders allows faster crank speed as does a fully charged battery for faster starter motor speed
So testing compression, even over a few hours will net slightly different results, over a few days larger differences, especially if temp is colder, it effects battery voltage alot and oil viscosity when cranking engine

If there is a head gasket leak between two adjacent cylinders, and spark plugs are in, this can skew results as well

WET test allows the oil to seal the rings better, so results should always go up on good or bad rings

For the Dollar Bill test to work you must have a misfire at the time of the test
If an exhaust valve leak is not big enough to cause a misfire then its not big enough to see the Suction at the tailpipe
This test is done to determine if the Misfire is valve related or spark/fuel related

Could the timing belt be off by a tooth on the CAM, maybe
Could be tensioner as well
There really is no test for that outside of looking at the Cam mark, and feeling the tension on the belt

 

I had all my spark plugs still in, ill try the test again with them removed. Battery died right after the test too, so that could've skewed the results too. The compression did go up like 3 to 5 psi on the wet test. Ill check the timing belt too. I has to be something top end related I'm thinking.

 

Slight increase on WET test means rings are OK, big jump means that cylinders rings are not OK

3 higher PSI and one lower PSI would mean cam timing is OK, and its a valve issue in the lower PSI cylinder most likely
All 4 being lower can be cam timing or just gauge or battery issue

In a 4cyl engine if one cylinder is acting up that's a reduction in power of 15 to 25%
Not only does the effected cylinder not add power but it takes away power from the crank to keep it's piston moving up and down

 

Alright thanks a lot for the info, I guess it's just time to start tearing into it!

 

Before tearing in, I would want to be sure the compression test had been completed with all plugs removed, AND a good strong battery. You mentioned yours was failing, and that can skew the test results, with the last one tested being more likely to be 'off'. If you started with #1, and it was the worst reading, then eh, what can I say?
A bit of carbon on a valve seat can cause poor readings. If you are not getting misfire, you are not losing 25% of your hp/torque with a weak cylinder. It will be reduced some, but as long as it fires regularly, it is adding to the power.
If you tear it apart, without actually checking the valve/cam timing with the cover off, or through the inspection port, you are guessing. Your choice. I would want to be sure I needed to take something apart before doing so. You can spend a lot of money and not get a lot of difference overall after doing a lot of work. I for sure would check the cam timing before taking it apart. If you don't burn oil, or not a lot, and it drives and seems to run fine, then your gain from spending a lot may be less than you expect. IOW, don't expect a 25% increase in power after doing a ring and valve job, for example.
tom