2.5L Running Really Rough at Idle ??????

[w chapman]

I'm trying to diagnose a problem in a 98 DOHC 2.5L (Legacy Outback) I obtained recently that's running really rough at idle and wonder if there's some wisdom from the Group.

First...engine would barely start and run....and CHK ENG light was on. An OBD-2 code reader showed "Misfire" on cylinders 3 and 4 which we diagnosed to no spark on either cyl 3 or 4 plug wires. CAT would get red hot from raw fuel being dumped from the non firing cylinders.

We replaced the coil and ignitor with known good ones with no success....gradually traced the problem to a bad ECU. Obtained a replacement for the ECU and NOW have all cylinders firing on full throttle but idle is still really rough and lumpy.

But I'm not getting any trouble codes on the code reader....even though the engine still runs (idles) really crappy.

i suspected the timing might be off...perhaps due to incorrect belt installation before I got it. Can this be checked with a timing light without having to pull the belt covers?

I checked the timing at the crank with a light....Spec is 20 degress BTDC at correct idle rpm of 600-800rpm. At my rough idle...which seems a little too low.. maybe 400 rpm....timing was at 14 degrees. A slight increase in idle to about 800 rpm send the timing mark to 22 degrees.....accelerate any faster and it climbs to well over 30 degrees. Any clues here??

Carfax report showed it was a "gross polluter" by couple of CA smog inspections stations and the coil had been replaced in it's last days with the PO.....before I got it.

I could use some more diagnostic tips to find this problem.

Warren C.

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[MrFisher]

Carfax report showed it was a "gross polluter"

Couldn't resist, too funny. Not that I'VE ever driven anything like that...

[gc822]

out of curiousity: I know you said you replaced the coil/igniter/ and ECU, but did you also replace plugs/ wires/ fuel filter etc... etc.. basically perform a tune up when you got the car?

As far as the timing questions go I can't help you there

[Boom05rs25]

Well im assuming it was a "Gross Polluter" because it was misfiring on two cylinders,dumping rawl fuel into the cats,this would be a polluter.....id hate to imagine how long it was drivin in that condition. Theres gonna be some carbon build up on the two former dead cylynders,this is only assuming it was drivin in this state "till it died".

Assuming you changed all the basics "plugs, wires,fuel filter,airfilter" Id start lookin in the direction of dirty injectors,try cleaning them replace if needed. IAC "idel air controler" is a possibillity as well,they get sticky sometimes. Dosnt seem to bad,thats were id start "IMO"

[w chapman]

Going in a "linear process" here....solve the biggest problem (no spark on two cylinders) first....

Next will be doing the standard "tune-up" options. Will be inspecting/changing plugs today and running a compression test while they're out. Fuel and air filters, etc.

The catalytic converter may have been damaged/melted/plugged, while the two cylinders weren't firing....it got very hot (red hot) once since I've owned it..trying to diagnose....who knows how many times with the PO.

It may be melted/plugged up....(a clue???)...I'm getting a loud "whistle" sound coming out the exhaust when I jam the accelerator hard.

WC

[w chapman]

Re: Removing, checking...and cleaning the injectors....

I've only tried to pull an injector once previously on a 2.2L and had a very difficult time of it...in fact ..was unsuccessful.

Can someone give me instructions on how to remove and test injectors without damaging them.

Warren

[Lethargic1]

My old Integra used to have idling problems. It was because there was a small crack in the distributor cap. I had it fixed a couple of times, but for some reason it would always come back after a while.

[w chapman]

Originally Posted by Lethargic1

My old Integra used to have idling problems. It was because there was a small crack in the distributor cap. I had it fixed a couple of times, but for some reason it would always come back after a while.

Come on....!!!! ??? There's no distributor on a Legacy Outback.

Wc

[Lethargic1]

Ok, I"m a freakin' idiot. Anyway, I found this on line, I hope it helps:

PCV (Positive Crankcase Ventilation) valves, part of the emissions systems, usually connect to a vacuum hose. They can become sticky or the rubber grommets can harden and leak. A vacuum leak can cause rough idle and acceleration. A problem in the PCV valve can cause oil consumption. If you have had a sudden increase in oil consumption, and no signs of other oil leakage, or other problems, check the pcv valve.

Also, here is a link with something else to think about.

Forum Link

[w chapman]

Can someone tell me how to test the IAC (Idle Air Control) valve for proper function.

Warren C.

[w chapman]

The good news is that we found out why.....even after a new computer gave us spark at all four cylinders.....the car still runs like crap!

The bad news.... the reason why........No compression on the #3 cylinder.

Engine rebuild (or replacement) time!


Warren C.

[2slofouru]

Sorry to be off topic, but if you figure out why your exhaust was "chirping" could you post it? Mine does that and I can't figure it out. I have one high flow aftermarket converter and 2.25" all the way back to a flowmaster muffler. Sounds good but the chirp comes out over the rumble when you're in the car.

[Lawsonmh15]

Maybe I don't know the whole story here, but have you pulled the plugs and/or wires yet? What plugs are you using.

I've had the Bosch Plat + 4's throw codes after about 7K miles. Can't completely blame them though. After pulling my 2 Week Old wires, I found that the inner connector on one of the wires was disconnected. The computer compensates for poor spark I believe, and the result was that one plug was fouled, while the other three were white (lean). Replaced with NGK's and OEM wires, and no codes or performance issues for about 3K miles. Good luck though.


UPDATE:

Looked at the Factory Service manual's Engine Trouble Shooting guide. Under "Initial Combution does not occurr" - Compression; the possibilities are: Loosened spark plugs or gasket, valve clearance, valve seating, defective valve stem, loosened cylinder head bolts, worn or broken valve spring, improper timing, and most often improper OIL (Low Viscosity).

[Lawsonmh15]

Fuel injector Service Procedure:

Click HERE