97 Subaru Legacy GT Exhaust Smells Extremely Rich!

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8,320
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New England
This has pretty much been the issue since I bought the car 18 months ago. The exhaust smells pretty strongly of fuel (mostly when cold) I also have the infamous P0400 EGR Flow Malfunction code. The EGR system works perfectly, but I've heard from some people that this code can be an indicator that the cats are starting to plug up. Any thoughts? Car runs pretty well and starts every single time no issues; however, I have noticed a decrease in mpg AND there is a slight hesitation when I first depress the accelerator. Plat plugs and wires are all 30k old. EGR is not clogged and, as previously stated, works exactly how it should, but code remains. I may grab my buddies laser temp indicator to compare the temps upstream/downstream of the cat
 
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hal

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393
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NC
just gut the cat. lol really, being that this is an obd2 car it should not just run rich unless your coolant temp sensor, idle air temp sensor, maf sensor (needs cleaning?), or oxygen sensor is bad. i have noticed that subaru's tend to have high exhaust temperatures, maybe a by-product of the flat-4 design i don't know. you may want to check your timing also, it could be too far advanced.
 
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beaver land EH?
 Originally Posted By: gathermewool
This has pretty much been the issue since I bought the car 18 months ago. The exhaust smells pretty strongly of fuel (mostly when cold) I also have the infamous P0400 EGR Flow Malfunction code. The EGR system works perfectly, but I've heard from some people that this code can be an indicator that the cats are starting to plug up. Any thoughts? Car runs pretty well and starts every single time no issues; however, I have noticed a decrease in mpg AND there is a slight hesitation when I first depress the accelerator. Plat plugs and wires are all 30k old. EGR is not clogged and, as previously stated, works exactly how it should, but code remains. I may grab my buddies laser temp indicator to compare the temps upstream/downstream of the cat
Perform all the proper pressure checks and testings: - pressure test (on car/off the car) for fuel injector leaks and such. -check pressure regulator to ensure that it's within operational pressure range (not too high or too low) -check thermostat for proper running conditions -compression check all your cylinders to ensure that the wet/dry reading is reasonable and within range -Check to see if your cat is lazy or intoxicated. If so, you may have to replace it. -check verify that your O2 sensors are in good working condition (is yours an OBD or OBD-II)? also: check your coolant temperature sensor to ensure that both the cold/hot range is within specifications (of course, validate against factory service manual and not just some half-aaase source) This is good for starters ....we'll throw in more as we go along. Q.
 
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beaver land EH?
 Originally Posted By: hal
just gut the cat. lol
Gutting the cat is the most irresponsible way of dealing with this situation, letting alone environmental concerns.
 

gathermewool

Thread starter
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8,320
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New England
 Originally Posted By: Quest
Perform all the proper pressure checks and testings: - pressure test (on car/off the car) for fuel injector leaks and such. -check pressure regulator to ensure that it's within operational pressure range (not too high or too low) -check thermostat for proper running conditions -compression check all your cylinders to ensure that the wet/dry reading is reasonable and within range -Check to see if your cat is lazy or intoxicated. If so, you may have to replace it. -check verify that your O2 sensors are in good working condition (is yours an OBD or OBD-II)? also: check your coolant temperature sensor to ensure that both the cold/hot range is within specifications (of course, validate against factory service manual and not just some half-aaase source) This is good for starters ....we'll throw in more as we go along. Q.
I'll make sure to look into these when I have some free time. The thermostat is working perfectly. As monitored by the scantool, she goes from OL to CL with in a minute on cold days, and with in 20 seconds now that it's warmer here in CT. Also, the RPMs rise to 1500 when cold and lower as the coolant heats up. Usually down to 1250 rpm by a coolant temp of 100F and down to nominal soon after. I'm not sure if the OL to CL cycle time is an indicator of a properly operating O2 sensor or temp sensor. I'm not going to go catless, but might consider a single high flow cat, which would most likely be better than the two possibly lazy cats. The only thing leading me to believe the cats are starting to plug is the P0400 code, which some one said could be caused by too high of an exhaust back-pressure. The main concern here is money. I got the car 20k+ miles ago for around $4k (after new struts and radiator) and don't really want to spend anything on it if I don't have to other than oil changes and other basic upkeep. I plan to run'er for another 100k if I'm lucky so if the cat does need to be replaced I'll do it. This is my DD, and I take the STI out on the weekends, so I'm not doing too well by the environment as is. I don't feel right about making it worse if I can easily, inexpensively fix this. Thanks for the help BTW : )
 
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gathermewool

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Update: P0302 Cylinder 2 Misfire Detected this morning Drove 180 trouble-free miles to the gf's place and back Tues/Wed. Car sat yesterday, Thursday. Car has been taking a little extra time to start in the past 4-5 months, but started reliably this morning; however, she stumbled the entire 6 mile trip to work. P0302 code popped up on the scangage II. I've been busier than I'd like, but it looks like I'll have to go ahead and change out the plugs asap to see if this clears things up. I've got a four pack of Bosch pl plugs around here some where. Any other suggestions?
 
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8,598
Location
Florida
 Originally Posted By: gathermewool
Update: P0302 Cylinder 2 Misfire Detected this morning Drove 180 trouble-free miles to the gf's place and back Tues/Wed. Car sat yesterday, Thursday. Car has been taking a little extra time to start in the past 4-5 months, but started reliably this morning; however, she stumbled the entire 6 mile trip to work. P0302 code popped up on the scangage II. I've been busier than I'd like, but it looks like I'll have to go ahead and change out the plugs asap to see if this clears things up. I've got a four pack of Bosch pl plugs around here some where. Any other suggestions?
Bosch plugs may cause new problems rather than fix the misfire. I have seen many people come in saying they tuned up the car, and it still runs poorly. Buy the plugs required by your owners manual, odds are they are NGK or Denso. +1 on replacing wires Does your car use a distributor ignition? If it does, you need to buy a distributor cap and rotor. Many times, old plugs and wires get replaced, and it only solved the misfire by a fraction rather than completely.
 
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