[shastacaster]

Hi all,

I've got an interesting issue and wanted to get a second opinion on something.
So first off, I have a 1991 RRC that I got from a coworker. He bought it in 2016 and left it in our company parking lot for 2 years, where it just sat until I got the keys and title a couple months ago.
I've changed all of the fluids and filters, and I even changed out the muffler (the last one had a rusty hole in it the size of a football)
Since I live in California though, the vehicle has to pass smog. Last Monday I took it in to be tested, and it failed horribly.
One of the few pieces of paperwork I was left with was the results of its last smog test, which it passed in March of 2016.

Hydrocarbons	Limit	2016 Results	2018 Results
Idle	120	5	468
2500 RPM	180	8	17

The exhaust has a noticeably fuel-rich smell to it, which would indicate a cylinder not firing. I changed out the ignition coil, spark plugs, and wires, but it still failed smog.

I brought my RR to a local British auto specialist, who ran a compression test on the cylinders.
All of the cylinders came back at between 120 and 125 psi, but Cylinder #1 came back at 45 psi
The technician suggested that it's a crack in the cylinder wall, but I find this really hard to believe: wouldn't the oil come out milky/frothy?
I'm willing to bet it's something more straightforward like a blown head gasket, but I'd love to hear anyone's take on this

Thanks

 

[Mikieman]

First off
You have do do emissions for something that old
Is a bummer
But I would check you oxygen sensors
Have you looked at the code reader
On the passengers seat
It is behind the panel next to the door

 

[Mikieman]

http://www.troublecodes.net/landrvr/

 

[JS5D]

Well if you have a low compression one cylinder you have found a problem that needs looking into.

There are obviously various things that cause low compression and since all the others cylinders have good compression, general wear of the bores is unlikely to be the broblem, most likely something is broken around cyl 1.

The Rover V8 started as a Buick 215 engine and then was adopted by Rover as a quick fix for the dated and underpowered engine range in the 60-70. Rover persevered with the design and gradually increased the boresize to increase the power, they kept the design going till 2005 or something in the D2 and P38 RR. It is widely known that at some point this bore increase exposed weaknesses with the steel liner in the aluminium block. The liner can crack or become loose in the block. All of it is bad as generally there is no fix for this other than fit a new block. Yes there are signs that this is the cause, but then there are the stories of there being no signs. Typically however you would see some interaction with the cooling system (pressurizing). Taking the head off, blocking the cooling water openings and pressuring the cooling system with air would show any liner cracks with soapy water. The internet has plenty examples of this issue and the process.

Alternatively something has gone wrong with the rings or a valve might have burnt out. Typically you can troubleshoot further with some basic techniques such as: add some oil in the cylinder and if pressure goes up, your rings are leaking (temporarily less so dt the oil). Solution would be to change rings or piston after checking bore for damage. You can pressurize the cylinder with air and listen for air leaking through the valves (leakdown test). If the head gasket leaks you would see the air pressure migrate out to the side of the block or adjacent piston. In your case Cylinder 1 is far removed from the water channel so you would not see a pressuring of the cooling system.

I just restored a 3.5, which is the most solid design (smallest bore, but also the least powerful). I received the car with one head removed 20 year earlier. So the chances that somebody had abandoned a no hoper cracked block were great. There were wooden blocks securing the pistons on the open side indicating somebody had done a leak test on the opposite side (block to stop the crank from turning when air was applied). Upon removing the other side I found the exhaust valve on nr 6 was burnt out (piece missing). So they removed the wrong head (poor trouble shooting) and the fix was relatively simple. So far the engine has been running fine for about 300miles..

 

[95classiclwb]

Hydrocarbons = too much unburnt fuel. check your timing, coolant temp sensor, vacuum advance, intake system for any leaks around intake gasket and or intake boot.
check thermostat. make sure your cats are not damaged and install a new set of oxygen sensors. take it on the highway and gun it to clear any carbon residues before going to retest. test it nice and hot, a hot engine dilutes better the HC's.

 

[shastacaster]

Like I said, I find a cracked cylinder wall hard to believe as the culprit when there are so many other factors that could be an issue.
The 02 sensors seem like a good place to start; a leakdown test would be good too. I'd rather replace a valve than an engine block
@95classiclwb, hopefully poking around at the intake gasket and boot might yield some answers that are simpler to address than removing cylinders or valves.

@Mikieman California can be a real pain to live in when it comes to owning older cars (or anything nice for that matter). My brother lives in Oregon and doesn't have to deal with smog or annual registration.
I'll see if the techs at the shop pulled any codes; I don't have an OBD1 reader.

@JS5D I've heard of the issues surrounding the 3.9L bore-out, and how the walls get to be awfully thin around the perimeter of the engine block. Didn't know they had offered a 3.5L at some point though; even though it's underpowered, is fuel economy at least marginally better?

 

[JS5D]

The 3.5L was the original size, which was replaced with the 3.9 etc and although it might retrofit since the heads and all are the same, it would be a severe downgrade. With the 3.5 you are talking 1970 power AND fuel consumption. They are suppose to be more robust but more "original feature" than desirable.

 

[shastacaster]

So, an update on the engine as of this morning:
A leak down test revealed that the piston rings on Cylinder #1 are the source of the misfire.
I would be thankful that it's not a crack in the engine block, but that brings me to my next question:
If the piston rings are the source of all my troubles, would pulling the piston out and replacing the rings actually solve my problems? Or would all it get me is a visual inspection to confirm the leak down?

Also, if anyone has experience pulling pistons, I'm all ears on pulling the inlet manifold to get to the head.

BTW, very unprofessional of me, but I bought a can of Engine Restore & Lubricant to see if that helps bring compression up in Cylinder #1.
Does anyone have any experience with this stuff? I'll be running a compression test this weekend to see if anything happens.

@JS5D less power and equal consumption is no bueno. I'm guessing the 3.5L is fitted with a carburetor?

 

[95classiclwb]

if you pull one piston may as well pull all, also could be fuel has washed the rings causing the misfire, squirt a few drops of oil, run the engine then recheck.
if you go for full ring replacement you may want to consider a 3.9 and complete engine overhaul.

 

[JS5D]

Yes this is a tricky situation:

1) you remove one head, so while you dismantled halve the top end of your motor maybe remove the other side as well.
2) New headgaskets, probably best to have the head skimmed. Lets hope they do that without insisting a a head rebuild. I suggest you refit with studs instead of bolts.
3) Now you drop the sump and open the big end on cylinder 1 and push that piston out (up). You see some wear on the bearing surface. Bearings are cheap, you might as well change that. Now you want to do them all.
5) You open a main bearing while you are there: some signs of wear so you change them as well (possible in situ, but a little fiddly). So that is the bottom end sorted.
4) Obviously you pull all pistons at this point.
5) You had to do something with the rings on piston 1 (assuming bore is not damaged). All pistons are out so, change all the rings.
6) Might as well give the bores a quick hone
7) We are assuming your cam shafts and followers are fine.

Ok so you can source another motor and swap ($), maybe more power if you like that (in a RRC?), but how is that motor going to be compared to your (overhauled) original engine?

You are in at the deep end now. Most people here are in the deep end, spending too much money on a car that is not really worth it commercially speaking. You can buy a good LR3 for $6-8k and drive it, lots of power, very capable and very comfortable. You have to like the RRC enough to endure the challenges.

 

[RRLondon]

If you need to comply with smog test so you can move it around, try unplugging number one injector to get it tested. No fuel there should stop the high reading.

Gives you a breathing space to then consider which direction to go.

If you lift the rocker cover or that head to assess if a valve is partly open / bent that would give a low psi reading. Although it should be rattling the tappet if that were the case.

 

[shastacaster]

@RRLondon: I like your thinking, it would definitely pass smog at that point and wouldn't make much difference in power output considering the pathetic 45psi output on Cylinder 1. At some point the rings will have to be replaced, and that's the real problem that has to be addressed.
@95classiclwb and @JS5D: when I pull Cylinder 1 I'm not going to deal with the other pistons. They're all firing on ~125psi and I don't see any reason to mess with them other than making preventative measures that, as an amateur mechanic, I could totally mess up and make worse by tampering with components that are otherwise working perfectly fine. If anything I'll replace the valves on Cylinder 1 since the old valves may not handle the new pressures exerted on them. Thanks for the recommendations though.

 

[95classiclwb]

@RRLondon: I like your thinking, it would definitely pass smog at that point and wouldn't make much difference in power output considering the pathetic 45psi output on Cylinder 1. At some point the rings will have to be replaced, and that's the real problem that has to be addressed.
@95classiclwb and @JS5D: when I pull Cylinder 1 I'm not going to deal with the other pistons. They're all firing on ~125psi and I don't see any reason to mess with them other than making preventative measures that, as an amateur mechanic, I could totally mess up and make worse by tampering with components that are otherwise working perfectly fine. If anything I'll replace the valves on Cylinder 1 since the old valves may not handle the new pressures exerted on them. Thanks for the recommendations though.

normally the piston ring kit comes as an engine set, you will be disturbing wear pattern on rod bearings which also come as an engine set. just an advice, replace all.

btw, if the HC's are high and only one cylinder is low compression, the possibility exists that the injector in said cylinder could be leaking thus washing the cylinder with excess fuel and your low compression readings.

try a replacement injector and a few drops of motor oil in the piston to help it reseal, it will smoke upon restart. drive, let it cool down and recheck compression. analyze results.

 

[shastacaster]

@95classiclwb After talking to a mechanic friend of mine earlier today, he said the same thing, so I'll be replacing them all. He also agreed that it could be a bad fuel injector, and that as long as things are being pulled apart, those should be replaced as well. I'll pick up a new injector and test it out, thanks for the advice

-Shastacaster