Low compression on No. 5 cylinder and rough idle

[Vipir]

Hi everyone,

I have a 2010 XR6T 50th Anniversary 6sp manual which is the love of my life.

It has 137,500 km on the clock and I have been having some problems with him.  Lately he has been idling very roughly which a number of people have informed me is the thrust bearing, but even worse is the check engine light issue I have been having.

No. 5 cylinder is the culprit for which I have had a coil pack replaced, new spark plug and a new injector. Compression tests today revealed a psi of 85 and my mechanic is going to do a wet test on Monday. He has told me to avoid driving it, which is difficult as I have 3 kids and work weekends.

If the test comes back with normal pressure, which I believe indicates ring problems, what are my options for repair/replacement of same?

If the test comes back with low pressure, which I believe indicates valve problems, what are my options there?

In either case, are there after-market parts available and, if so, where would be the best place to get them as I am not flush with money but want the best value.  Do you guys think it's worth working on or should I cut my losses and trade in for the best price and get a car with no personality and one I won't be at risk of getting attached to?

Should I be worried about the thrust bearing? My clutch is not affected, but he idles like a tank and sounds awful.

I really appreciate any advice as I have spent pretty much most of the afternoon stressing about what I am going to do for transport.

Thanking you in anticipation of your help,

Leonie.

Edited 19/02/16 10:12 AM by Vipir
Added extra tag

[gaz097]

I'm not sure what a thrust bearing is causing a bad idle. But I'd be getting a second opinion if that's his diagnosis.

As for the low Comp your screwed anyway there. Either repair or replace as won't be cheap.

[Vipir]

Thanks, I was kind of hoping for a bit more information. I know it's not going to be cheap, but I was after information about parts and cost, not having the obvious stated.

[k31th]

Dangerously low compression in a single cylinder means remove engine, pull off head and inspect cylinder in question, apply replacement parts or repair parts in question, refit head and relevant gaskets and refit engine. (minimum $1500 in labour plus parts, at a guess). Or it is remove engine and refit replacement engine. 

If it is not in warranty in any way, check with a forum sponsor with regard to potential costs for such a repair and weigh up whether it is possible to outlay a significant sum to repair. If you can't afford to repair it then trading it in is probably the only viable option. 

I sincerely hope the engine isn't damaged. Good luck with it all. 

 

Edit: with regard to prices, a short engine from Ford is probably the cheapest and best value way to make it back to factory condition or better. All other parts that are aftermarket are usually for performance and are significantly more expensive as they are much better quality. 

Edited 20/02/16 12:53 PM by k31th

[gaz097]

Basically what I said ^^

If it's a piston issue, best way would be Fg short motor plus labour. Maybe 4K total.

If it's a valve issue you could find a good condition second hand head for about 500 bucks, plus labour so 1500 odd.

[MattyP]

Isnt it better to build an na motor from the wreckers?

[boost69]

I'm no mechanic but wouldn't a bent rod also cause low compression and rough idle?

[Vipir]

So tomorrow (we hope) my mechanic is going to do a wet test. I'm praying it's "just" a valve because once we start getting into the bowels of an engine, I think costs start to increase by lots of $500.

Thankfully, the piston appears to be undamaged.

I don't know about rods or anything! We'll get a better idea of what the problem is tomorrow (hopefully, if he's got time).

Please keep fingers crossed for a simple fix.

Every time I see an FG I ask them, rhetorically, if they've had compression problems. Then maybe I wouldn't feel quite so alone...

[k31th]

How'd it all go?

[Vipir]

Thanks, for asking...

Turns out it's the rings. Of course it would be, because if anything, I was hoping for the valves to be buggered. But that was simply not to be.

My mechanic is going to check the bore for damage (pray God none) and then get to work on replacing the rings. 

I could weep. I don't bag this car - I drive it carefully and respectfully (I open up the throttle a bit on the back roads to clear out his pipes, but gradually through the gears) and yet this has happened.

I now can't pass an FG without wondering what they've got going on under the bonnet.

I can't think of anything I have done to this car to have the rings go. 

If the rings in this cylinder have gone, when will the rest go? The other cylinders are compressing well, at this stage.

I think I will get this car repaired and look to replace it with something that has no personality or presence and just keeps its head down - like a Camry. Maybe a 50th Anniversary XR6T 6spd manual isn't such a pleasure to own with all this stress and expense.