98 Forester, EJ25D 2, 4 misfire

[Mr. Carb]

***SOLVED*** Original message below:

 

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Finally got my computer to throw some pending codes.

 

After a drive on the freeway, idle is rough when I give ever so slight throttle to the car, such as when attempting to park. Anything between 800-1200 rpm is really rough.  I held it at that rpm to get the ecu to throw codes, P0302, and P0304, Cylinder 2 and 4 misfire detected.

 

I would think if it's a cam issue it would be rough throughout the rpm range.  Coil issue maybe?

Edited August 23, 2014 by Mr. Carb

[1 Lucky Texan]

check for oil in the plug tubes. If the valve/cam cover gaskets leak oil in there, it creates a high voltage short.

[Mr. Carb]

I check there often and haven't seen any oil leaks yet (they are new seals as the head gaskets and all other gaskets have recently been replaced).  I will check again tomorrow during the daylight to see if something is going on.

 

Also noticed an intermittent lifter noise on that side of the engine, the two may be related I'm thinking now.

[86BRATMAN]

With the solid lifter buckets there shouldn't be intermittent noise, it should either be there or not. You may have another issue surfacing or you could be hearing detonation. It is possible your that your timing is slightly off, the 25d is rather sensitive in that respect. Might be worthwhile to pull the timing belt covers to be sure everything is lined up properly.

[johnceggleston]

check the timing,

2 & 4 are both on the driver side.

 

has the car been running like this since the head gaskets were done?

or is this a new development.?

[Mr. Carb]

This is a new development, the intermittant noise started about a month ago, the idle issue started after I cleaned up some vaccume lines and replaced the coolant temp sensor, though I would think if that work was related to the idle issue that cylinders 1,3 would have issues too.  I'm going to check plug wires and timing later today and see if it slipped a tooth.  It's a newer timing belt with new idle pullys and tensioner as well, all was replaced 10k miles ago.

[Mr. Carb]

check the timing,

2 & 4 are both on the driver side.

 

has the car been running like this since the head gaskets were done?

or is this a new development.?

 

Timing it is, at least the lower cam has slippsed 1-2 teeth, I didn't even compare them to the crank.  Bought a new timing belt because I suspect this one was stretched at this point, will be replacing it tomorrow and see how it runs afterwords.

[Fairtax4me]

Jumped timing is generally caused by a failing (loose) belt tensioner. Replace the tensioner and all of the idlers, as well as the water pump.

[johnceggleston]

what he said.

modern belts rarely fail.

usually it is another part that has not been replaced in 120 - 180k miles.

[Mr. Carb]

Well, after a second more extensive look, belt is fine, timing is fine.  So much for that theory.  The belt, tensioner, and all other idlers/water pump was replaced about 10k miles ago.  No oil leak at the spark plugs, so at this point I'm not sure what causes the 2 and 4 misfire at 900 rpms (only after a freeway drive) or the intermittent knock or per-detonation sound that comes from that side of the engine.  Silly problem-matic EJ25D's.   I'm looking at possibly trading the car in for an impreza.

[1 Lucky Texan]

if, after warming up, you can have a helper hold the RPMs in the failing/rough range - try spraying something like Ether Start around the intake manifold - maybe the vacuum lines too. Just incase higher temps are causing a gasket or other intake parts to fail.

 

in some older soobs, crank sensors would be intermittent/fail at higher temps.

 

freezeframe or similar data might help pinpoint a system that is marginal too. Some OBD scanners can get that data. Other methods can get more data or even show live data.

[Mr. Carb]

I have an ODB II live scanner that I can plug in, that's how I found out 2, and 4 were misfiring. Not enough to apparently throw a check engine light, they are only pending codes. However everything else looked normal.  Given that the driver's side head is also the head that the cams are loaded when installing the timing belt, I couldn't help but wonder if the valves might have gotten slightly tweaked if one of the cams sprung to a neutral state during timing belt installation. Slight collision between an intake and exhaust valve maybe?  I'll have to get it to start to misfire again and start spraying for a vacuum leak, though I find it odd that a leak would only affect one side of the engine.

 

I'll also check the crank and cam sensor and see if something is getting flaky there.

 

Sometimes I wonder if these ecu's are way too forgiving since I can tell there's a problem long before a check light ever comes on.

[1 Lucky Texan]

another item that can cause issues in an RPM 'range' would be the TPS. But don't most people have an engine 'cutting-out' symptom with TPS problems?

[Fairtax4me]

How old are the plugs? What brand and type are they? Copper, platinum, Iriduim?

 

Spring pressure closes the valves. If a cam slips out of position the valves are closing, and would not be able to hit another already closed valve.

 

Have you checked Valve lash clearance? It's common for the 25D to burn exhaust valves, though that typically only occurs in one cylinder.

[Mr. Carb]

TPS?  Tire pressure system?  98, doesn't have that. 

 

Plug are newish, NGK platinums. They were put in about 15k miles ago.

 

On valves I was noting that because both cams on 2,4 side are in a loaded position when at set timing marks, makes it possible I read for an exhaust valve to collide with an intake valve if the cam spins from the loaded timing marked position.

 

At this point short of a vacuum leak, it is probably a serious cause, involving taking things apart to find out, not sure the car is really worth that much work after just doing all that work to it already.

[1 Lucky Texan]

sorry, Throttle Position Sensor

[Fairtax4me]

Single Platinum or double platinum? It makes a difference in waste spark systems. Did you try to re-gap the plugs before putting them in? That's a big no-no with platinum and iridium plugs.

 

I would put a set of regular copper plugs in it and see what happens.

 

On valves I was noting that because both cams on 2,4 side are in a loaded position when at set timing marks, makes it possible I read for an exhaust valve to collide with an intake valve if the cam spins from the loaded timing marked position.

 

This is not possible unless both cams are drastically out of time. The intake and exhaust valves are not open at the same time on the same cylinder when the timing marks are aligned. So if the cam snaps out of place, the valves simply close.

There is a slight amount of "overlap" where the valves will be open at the same time, but they are open only slightly, and only for about 30° of camshaft rotation. For any valves to collide they would have to be nearly wide open.

[Mr. Carb]

Single OEM Pre-gapped.  I know better than to re-gap platinum plugs.

 

Throttle position sensor, I was looking at that, the scanning tool I have isn't showing me any signal from it at all very consistently.  Wouldn't it throw a code if it was intermittently reporting a signal though?

[Fairtax4me]

Single OEM Pre-gapped. I know better than to re-gap platinum plugs.

 

And there-in lies a problem. OEM plug is copper. NGK BKR6E-11.

 

If you want to use platinum, they need to be Double platinum. The waste spark ignition will wear the ground electrodes of single platinum plugs on one bank. 2/4 bank is the negatively polarized side of the coil, and you'll probably find severaly worn ground electrodes on those plugs. Run doubles or run copper.

[Mr. Carb]

Ah ha.   Well then, I will attempt to change them without removing the engine, it looks tricky. I thought they were platinum's not copper as they were supposed to be the 60k mile ones for the DOHC, don't remember if single or double. I will report back after that work is done.

[Mr. Carb]

Pulled spark plugs, they were the quad fire platinum's apparently. Only one still had some electrode left.  Replaced with single fire iridium's.  There was no oil in any spark plug well, no oil on any of the plug wires. Got the car warmed up, it's running better at all RPM's except after a drive.  Once it's driven it is back to the same old misfire on cylinder's 2 and 4. 

 

I'll check again for vacuum leaks, but did not find any last time I checked, I still hear the intermittent lifter or knocking sound faintly on that side of the engine as well.

[Mr. Carb]

I checked for vacuum leaks again, found none.  Decided that maybe it is the coil pack gone bad.  Spent the big $$ on a new coil pack from Carter Subaru, put it in (took me about 3 minutes) last night.  Test drove the car and it had no more misfires.  All day today same thing, no misfire.  I would have to say apparently it is possible for the coil pack to fail in such a way that 2/4 misfire when 1/3 do not.  I think it was an insulation issue because the old coil pack was very crusty feeling underneath and had several cracks in it from old age, probably the original on a car with 235k miles on it.