I had posted a thread on this truck previously and worked through a blown head gasket and leaky valves. 1996 Ranger 2.3L 2WD -New Head gasket, Valve job, plugs wires, fuel injectors, ECM, EGR, etc done with previous valve job.
We got the truck running pretty well and used it for a few months. lately we had an issue where it seemed pressure built up really high and was blowing oil everywhere. Intake was had wet Oil throttle body etc. Using this form and research it seems that the Cat was clogged causing high engine pressure. So replaced the cat. The truck started and sounded as good as it has since we owned it. However, after driving it seemed it still could have a bit more power, but not bad. Did still see smoke from burning oil we thought.

Decided to pull plugs and clean and check, replace PCV given all the oil and see if we noted any other issues. Plugs looked pretty good and consistent. Put it back together and started. It ran rough and would not idle. Eventually died and will not restart now.
Lastly I just performed a compression test. 1st 3 cylinders were from 120, 125 and 131 psi. Cylinder 4 by firewall is only at 60 I checked it twice. I then put in a few ounces of oil and rechecked that cylinder. It is at 90 now so assume rings. But truck should still start and run shouldn't it?
I used SF in throttle body and no start. I have not done fuel pressure check yet but do have fuel in the rail (depressed schrader valve). Used inline spark tester on plugs and have good consistent spark. Truck has strong battery and cranks good.
Any advice on next steps?
Could a clogged cat have caused some additional damage? Previously as I stated we removed the head, lapped the valves put new O rings etc when we had the blown head gasket.
thoughts on potential issues or next steps?

Eric

 

A 1996 2.3l should be 165psi on compression test, but could just be gauge is reading low, if possible test on another engine

120psi is about the minimum compression to start a cold engine, could timing belt have skipped a tooth?

Clogged exhaust can cause burnt exhaust valves, overheats them because there is no flow out, warps them

60psi should have gone closer to 120psi(like the other cylinders) when oil was added if it was a ring issue in that cylinder
Add oil to a 120psi cylinder and see what it goes up to

Excessive Blow-by(engine internal pressure) can be caused by clogged exhaust and that could have effected rings in all cylinders, not high on the list but possible
How many miles on the rings?

 

Over 180k on rings I'd say. When we had previous issues I tested compression and the non affected valves were 140+ with this gauge. I'll check on another engine when back home. Also will add oil to the 120 valve.
thanks as always for your help.

 

Rings and pistons usually last 400+ k miles, same for bearings

Exhaust valves are where low compression issues usually occur, it's the the nature of how piston engines work
Intake valves are cooled by incoming air and fuel
Exhaust valves just run hot all the time, if they get too hot, then they have problems


Metal on metal is never a good air seal, so will always leak air, but compression is a temporary thing, only needs to last for a second or two, to heat up the fuel to vaporizes it
The oil(any liquid) will help rings seals better always, hard to force a liquid thru any gaps, lol
But it won't help seal leaks in valves

So adding oil will always increase compression readings in any cylinder, even on a brand new engine
The increase in "good" cylinders, vs low cylinders can tell you if its rings or valves that are leaking
i.e. if adding the oil gets compression up to what "good" cylinders have then its a ring issue

Leak down test is the best one to determine rings or valve leaks

 

Ok thanks again you are always so helpful. I also never knew a clogged cat might cause so much issues.

It seems like the internal pressure was so high that it forced the dipstick out was blowing oil out there as well as the small vacuum hole that's supposed to go to the intake tube. (MissingVacuum line). There was oil blown everywhere underneath the engine on top the engine etc. We have no drips or leaks any place I can only assume clogged cat. And perhaps damaged valves or rings

 

When any piston engine fires the explosion creates enough pressure to push the piston down which adds power to the crank, that's what makes the whole thing work, as far as powering a vehicle

Because the pressure is so high there will be "Blow-by", this is the name for the gases that are created by the explosion that blow-by the piston and rings and into the crankcase, exhaust gases
Blow-by is also what creates the oil vapor in the crankcase and valve cover area, the explosion in the cylinder is the only place in the engine that is hot enough to vaporize oil, so as this high temp gas blows-by the piston and rings it vaporizes some of the oil coating the cylinder walls and rings/piston

Blow-by creates a pressure in the crankcase and valve cover areas since they are connected
In the old days there was a vent on the lower block or upper oil pan that vented blow-by out into the air
Since it was exhaust gases it was/is a pollution issue, so the PCV(positive crankcase ventilation) system was added
PCV system uses engine vacuum to suck the blow-by gases back into the engine to be re-burned

When exhaust pipes are clear the pressure in a cylinder is 0psi after exhaust valve closes
If exhaust is plugged up then pressure is not 0psi, could be as high at 60psi, so when intake valve opens that positive pressure will go into the intake and blow off vacuum hoses, also blow-by continues the whole time into crankcase so way too much for PCV system to handle and oil vapor(and blow-by) starts to come from any and all openings including dipstick tube

 

Just an update RonD. Due to all the oil in the PCV reservoir (catch tank), plugs are black with soot, soaked intake and oil dripping also truck would no longer start and run we went ahead and pull the engine this weekend. This is a 2nd vehicle for my son so this is all about teaching him how to work on combustion engines, value of the money he puts into etc. So perhaps not necessary to have pulled it for mechanical reasons we agreed to do it to learn more.

No visible issues with engine without disassembling bottom end. Head and seals looked great. Cylinder walls or as much as we can see look good. no visible piston issues or stuck or broken valves.

At this point we will be doing a leak test on the valves again.

Now that we have it completely out what do you recommend doing? Should I go ahead and hone cylinders and replace rings? New valves, lifters etc?

Again thanks as always

 

Always do a "Valve job" with head off, and pressure test, don't always have to replace all the valves but there are just 4 exhaust valves and those are the ones that fail/burn

You describe high Blow-by, i.e. from the oil coating in intake so i would rebuild the low end, i.e. bearings and rings

Blow-by is the exhaust the blows by the rings when a cylinder fires, all piston engines have this, this HOT exhaust vaporizes some of the oil on cylinder walls and sides of pistons, only place in the engine that gets hot enough to vaporize oil
So high oil vapor condensed in catchcan or in intake can only come from higher blow-by in lower end not from any valve issues

 

Thanks RonD. Bought new connecting rod bearings today and a set of rings.

Just a fun fact the catchcan for PCV was 100% full of oil.

 

Now that's some major blow-by issues, lol
Or really really cheap oil

 

Yes, it was full synthetic high mileage with low miles.

Only thing we can figure is cat was shot.

 

Follow up after complete tear down 2 of the pistons have racks around the rings and when we took them out the thin material between the rings chunked out. Valves are very black on the tops. plugs have heavy carbon on the strap and around base. Cylinder walls still seem ok with no gouges.

Question with the very heavy blow by we thought it was a clogged Cat. However, the Cat is "empty" any idea on what would have created this heavy blow by? At the time the issue was really at its peak it blew out multiple quarts of oil.

Im in the process of buying new parts now.

 

Well each cylinder generates 1,000+psi when it fires and if the rings are not holding the pressure in then there would be A LOT of blow by in crankcase, even with 1 cylinder doing it

Clogged exhaust(Cat) will limit RPM for sure but not increase blow by that much, it would limit the intake of fresh air/fuel because back pressure in exhaust system prevented all the exhaust from exiting the cylinder so next firing of that cylinder would be less power(limited RPM) IF it fired at all

Blow by is usually just a few psi, leaking rings ramps that up pretty fast, almost like the crank case is a tail pipe, lol

 

Ok thanks RonD as always. So just to be clear. if the valves will lap and seat properly I can clean this carbon off and change the o-ring they should be ok to reuse?

 

Not sure what o-ring?

But yes on the valves, if they can get a good seal then reuse them

 

Thank you it's just the little tiny O ring that goes around the valve stem between the head and the bottom end I believe. I already purchased them.

 

Valve guide seals?
They are important and need to be changed whenever valve springs are off

 

Just a last update on this thread. We went ahead and rebuilt the engine. Put everything back together and truck is running solid. Does well. Have done the initial oil change and will do another soon. Well we now have way more money and time in the ranger than in most peoples minds than its worth but we have learned a lot. We have a few things to finish up like getting AC charged etc but all in all pretty happy with it finally. Thanks for everything RonD. Without you much of this would not have happened.

 

Thank for the update, and good work

Cost of major repairs on older vehicles need to be looked at long term
If you have a vehicle that doesn't run well or at all, lol, and it's worth maybe $3,000 as is and you spend $3,000 to fix it up so its driveable then you break it down by cost per month to drive it
If you think it will last you another 3 years/36 months
That's $83/month to drive it, not a lot of use vehicles around for $83/month payment, lol
After the 3 years its 0 cost

The value of any vehicle for resale obviously changes over time but its the cost to drive it that matters
On any vehicle there will always be the same cost, in tires, brakes, oil and fuel
New engine and/or new transmission factor in as cost per month vs selling it and getting another vehicle, and the difference in extra money you have to pay out as cost per month for the newer vehicle

 

Very True RonD. I never liked when folks said something needed to be traded due to it "Nickle and diming" them. A $600 payment just steps over the Nickle and dimes. :-)

I have a posted a brake question if you have time to take peak. we rebuilt the drums and having an issue.

Thanks for everything.