advice on motor problem

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BILLANDLISA HORTON

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My 03 sporttrac started missing the other day so bad that I had to have it towed in to the dealership. It has roughly 170,000 miles with no prior troubles. always taken really good care of. It was jumping bad w/check engine light on, no smoke.



The dealership said that the diagnostic test said it was in cylinder 1, so they checked the plugs, plug wires, coil pak, injectors, etc....and said all checked out. THen they did a manual compression test and said that the compression was low in that cylinder and that it was in the motor......valve, rings, something expensive in other words.



They said it would cost me around 5 or 6 hundred dollars just for them to tear into it and see what the actual problem was.



Never having had anything to this degree tear up on a vehicle, I was really leary as to whether I was getting a straight story and if anyone here may have some advice for me.



I decided to have it towed to another place today for a second opinion, and it should be checked out again by tomorrow evening.



Is there anything minor that this could end up being? I'm at the mercy of the mechanic. Any advise at all would be greatly appreciated. Thanks
 
Some St's have known to break a valve spring.....



IF that is the case it is a couple hundred dollar repair...



UNLESS the valve hit the piston then it is a tear down of the engine..



Todd Z
 
What did the spark plug look like was it white or black? Does the miss go away at any point? Is it more pronounced in the morning or after the truck is hot? It could be a intake leak, Cam lobe worn out, valve burned, etc. Is there excessive crankcase pressure? if there is then piston & rings could be the problem. There is a miss problem I think that relates to an intake vaccum leak. What is the IAC count? There are a lot of things to check and a lot of things it could be. The 4.0L has been a good engine for me and I haven't had to change one out yet.
 
If the valve is bad and hit the piston would the compression be low or zero? If this started missing just in one day, I would look in other directions. Let's see what the next shop has to say. Could this be a timing issue for just that cylinder?

Good luck B&L Ed
 
If the valve is bad as in it is cracked, the compression would be lower as compared to the other cylinders.



If it is bent and truly not seating against the head, then the compression would be very low. Maybe not zero, but could easily be a reading of 25 PSI or even lower..



As Todd mentioned, it is not uncommon for the Trac engine to have some sort of a valve or valve spring issue as it gets some miles on it. Further, for those that have had this issue, they never really had a clue or warning, it just happened...



Bill / Lisa...

You really need to get the information from a compression test. Here is some information that will help you...



Ok, all cylinders but 1 are about 150 psi for example, the issue is with that single cylinder.

Retesting the cylinder by spaying a substantial amount of WD40 or something to that effect and...



If the reading goes up to NEARLY that of the other cylinders it is an indication that the piston rings are worn or broken or the piston itself has a minor crack in it.



If the reading goes up only a little bit, it is an indication that the issue is with the valve. If this is the case, it is repairable by removing the top end of the engine. Which is more affordable than the bottom end as you MUST open both the top and bottom of the engine.



With 170,000 miles, if it is more than a valve, I would seriously consider replacing the engine with a low mileage used engine. It will be cheaper then a bottom end repair and not all that much more than a top end repair..



If you need further help in figuring things out, simply post here or e-mail me and I will help you understand all that your options are or if the estimates they are giving you sound right or not..



Good luck...



 
Before you do anything else; disconnect your battery, leave it disconnected for about 30 min. reconnect it, and see what happens. ST's have a tendency to do weird things.
 
There is some good advice here however a compression test only tells you that the piston is moving up and down and making some sort of pressure, other than that it tells you nothing of any value even if you put oil in it. If you want to know where the problem lies exactly your mechanic needs to do 2 things. A compression test to find the low cylinder (already determined if you believe the dealer) and then a cylinder leakage test on the affected cylinder, this will tell you Exactly where the problem lies. One other step could be taken and that is to do a running compression test on the affected cylinder but most mechanics out there don't know how to interpret the reults.
 

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