'99 outback wagon with rear end noise, check engine light

[dtaffe]

I have a 99 Outback Wagon with 115k miles. It has developed a low-pitched non-metallic (I think?) thunking noise in the rear end, worse in warm weather, which occurs only on tight-radius turns, such as turning into my driveway or a parking spot, never while driving down the road. It occurs with both left and right turns. The thunking frequency is speed-dependent (faster thunk at higher speed), but the pitch is not. My mechanic (trusted) took a couple of tries to diagnose it (initially intermittent, always seems better when I bring it in,) but feels it's the rear differential. He's estimating $2k-$3k (big range, I know) to replace the differential. The last time I had it in (a month or so ago) he also noted that the clutch is starting to go (intermittent difficulty getting into first/reverse while stopped, decreased throw distance on the cluth pedal.)

 

As a final issue, my CEL has come on. Took it to the dealer, who said it was a spark issue, changed the wires (but not the plugs, which he said looked fine.) No better, he said to ignore it; they "splashed water on the coil and got no short circuit", so that probably wasn't it, and I could end up spending a lot of money without finding it. The engine runs fine (for an engine with 115k miles) although my gas mileage seems to have dipped a bit (275 miles per tank instead of 320 miles per tank.)

 

At what point, given all that needs to be done, am I throwing bad money after good? Does the thunking diagnosis sound reasonable, and what should I expect to pay for repairs? How would you go about addressing the check engine light? (I'm guessing I need to get the exact code as a starting point.) Another forum suggested using seafoam; one poster here seemed to have engine/emissions problems as a result, although the majority seem impressed by the product. Help!?!

Danny

[nipper]

You started throwing good money out when you bought that BS line from the dealer.

 

Go to a chain autoparts store and have them read the code. Tell us what the code is.

 

That dealer is an idiot, he never looked at the spark plugs. There is a lot of work to remove the plugs, and he missed an opportunity to sell you new ones. He is not going to pull plugs and reinstall the old ones. I bet he didnt even yank them.

 

We cant even begin to tell you what is causing the CEL untill we know what the code is.

 

Rear noise can be as simple as time for brake pads.

 

nipper

[johnceggleston]

Rear noise can be as simple as time for brake pads.

 

nipper

 

and 2 -3k$ for a new rear diff is outrageous. i think they cost 500$ new and less work to install than a trans, 300$ max. i don't think the mechanic knows subarus.

[Cougar]

I suspect the code you will find out to be is P030?. This is the code for a misfire problem and the last digit tells what cylinder it is. I wouldn't worry about using the Seafoam. It may solve the problem. First verify that my hunch is correct.

[dtaffe]

Ok, so a couple of things. I checked the codes. Sure enough, I got P0303 and P0304 (#3 and #4 cylinder misfire, according to the reader.) I also picked up a can of seafoam (I need to figure out where the vacuum intake hose is) and will try this tomorrow.

 

I also checked the clutch (a recommendation from cartalk.com) by trying a standing start in 3rd gear @2500 RPM. The car bucked and stalled (I didn't feather the clutch to "force" it to work). Maybe the clutch is ok?

 

I probably need to find a good repair manual for this car. What publishers do people recommend? Chiltons? Other?

[nipper]

Clutch is fine. Thats the std clutch test when the clutch is supect.

 

It may be the coil is tired. They are waste ignition systems. That means 1-2 and 3-4 fire at the same time. When you get a misfire on both it usually means its a coil issue. Beofre you replace the coil, swap around the wires and see if the problem moves.

 

You should still get a set of plugs.

 

 

Haynes is a great manual, chiltons is bad.

 

nipper

[dtaffe]

Clutch is fine. Thats the std clutch test when the clutch is supect.

 

It may be the coil is tired. They are waste ignition systems. That means 1-2 and 3-4 fire at the same time. When you get a misfire on both it usually means its a coil issue. Beofre you replace the coil, swap around the wires and see if the problem moves.

 

You should still get a set of plugs.

 

 

Haynes is a great manual, chiltons is bad.

 

nipper

 

Sorry to be a dunce, but anything more specific on "swap the wires?" Say I swap 1 for 2 and 3 for 4; if it's the wires, I should get misfire messages on 1 and 2. Right? What if the coil's the problem? Would I still get a 3&4 misfire reading?

 

I looked on the NGK website for plugs, and they have several that seem compatible, ranging from $2.50 per plug to $11.50 (and one set that splits the difference.) I'd guess the most expensive are the best, is that what I should get?

[Cougar]

I think Npper meant exchange the coils so the coil for 3 & 4 will move to position 1 & 2 and vise versa. Then if the codes change to misfire on 1 & 2 you can bet the trouble is with the coil.

 

I would get the best plugs myself but you don't have to. The better the plug is the longer you can go without changing them. The best ones may last you 100k miles. I recommend you put a small amount of antisieze compound on the theads. So they will be easy to remove later on.