Low Compression on Cylinders 2 and 4

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Carl Keef Jr

Member
Joined
Jul 29, 2020
Posts
22
Reaction score
2
Location
Cedar Park, TX
2010 Ford Expedition 5.4 3v - My mechanic (Christian Bros Automotive) just told me that he did a power balance test on my engine and it shows that cylinders 2 and 4 have very low compression. He said that it is either a cylinder leak, a cracked head, or a cracked engine block. He recommends a new engine and said it would be between $10,000 and $12,000 (parts plus 25 hrs labor). The engine has 186,000 miles and idles rough and has lack of power when accelerating. No CEL codes are being thrown. It has all new timing components, rollers/followers, new spark plugs, boots and springs, new heater and radiator hoses, upgraded oil pump, new MAF sensor, all new O2 sensors. Pretty much anything that I touched when doing the timing job was replaced with new OEM parts. I'd appreciate any thoughts on what you would do next. I don't really have the money for a new engine or to go buy another vehicle but this one is due for inspection and registration this month and won't pass in the current condition (because it shows P1000, On Board Diagnostic System Readiness Test Not Complete) which means that I would be risking getting a ticket for expired registration if I keep driving it. Thanks!
 

peterwells

Active Member
Joined
May 13, 2005
Posts
35
Reaction score
22
Carl,

I've a few things to share but no answers...

(i) $10-$12k sounds expensive for an engine, last time I looked a refurbished engine was less than $5k, $8k with labour is what I'd expect.
(ii) How low is very low compression? See this thread for my experience, I'm left believing compression data should be treated with caution, btw that engine has now done 4k miles and is running fine. https://www.expeditionforum.com/threads/looking-for-advice-on-low-compression.50820/
(iii) Is this a vehicle that you can afford to take off the road for a few weeks? If you can having done the timing you can tackle removing a head.
(iv) How long has it been since you did the timing work? Are the problems you're seeing related to that work? (had to ask)
(v) Why is it showing P1000? Was it reset by the shop? It should take 100 miles driving to clear that.


My experience has been that with basic care these engines will go a long way, if you don't already have it get ForScan for diagnostic info. I'd do the simple checks like switch coil packs, mess with the injectors, perform compression checks, leak off checks, check for communication between the combustion chambers/cooling system. Don't jump off the deep end without verifying what the shop is saying, that was my mistake.

Peter
 
Last edited:

JimR_TN

Well-Known Member
Joined
Oct 30, 2022
Posts
93
Reaction score
61
Location
Middle TN
Can a power balance test actually say compression is low? My understanding was that it was just the contribution to the power. Wouldn't a compression test on those cylinders be required as a follow-up in order to determine if the compression was actually low?

I took 2 vehicles to our local Christian Bros Automotive. Both came back that they needed an engine with a very high price tag. They both did have problems, but for my diagnostic fee they were never able to tell me any specifics on what was wrong or the reason why an engine replacement was required.
 

Dahammer

Well-Known Member
Joined
May 23, 2023
Posts
63
Reaction score
23
Location
New York
I would do a compression gauge test on every one of those cylinders. One at a time, write down those readings for each one. It could be bad rings, head gaskets, etc.

Check your local junkyard, also. Some yards test the engines to make sure they run.
 

bodabdan

Full Access Members
Joined
Jan 6, 2023
Posts
110
Reaction score
64
Location
River Valley AR
Contribution test is not the right way to check compression. It can only tell you if a cylinder is not acting correctly (contributing its fair share). Defective plug, coil, cam lobes, roller followers, hole in piston, all look the same to a contribution test. It's great for pointing out where the problem is, not what it is.
I would pull plugs on 2&4, check compression and leakdown. Swap coils and injectors with good cylinder, see if the problem moves. If that checks good, pull the valve covers and inspect.
 

Latest posts

Staff online

Forum statistics

Threads
53,396
Posts
500,653
Members
46,812
Latest member
Dcleghorn01
Top