Impreza_WRX_STi Posted April 19, 2004 Share Posted April 19, 2004 1998 Impreza OBS 77K 4EAT At a stop light or stop sign, if I take off a little more than light throttle (say 20-30%) The car will stumble. Once it partially backfired when I let off the gas to prevent it from stumbling. It will come out of the stumble as soon as I let off or 3000 RPM's. I have drove impreza's since 1996. I have no CEL coming on, and I havn't pulled codes, but I think it may have to do with fuel. Max Quote Link to comment Share on other sites More sharing options...
Setright Posted April 19, 2004 Share Posted April 19, 2004 This is just an idea: Your airflow sensor might be damaged. Do you have a non-standard intake system? Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 19, 2004 Author Share Posted April 19, 2004 Stock everything, besides rims/tires Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 20, 2004 Share Posted April 20, 2004 first is the gas in the car contamainated ( water in the tank, bad gas ), second i would check fuel pressure because low fuel pressure will not set a check engine light, another part that does not make the check engine illuminate is the nock sensor,but it will set a stored code. Quote Link to comment Share on other sites More sharing options...
Commuter Posted April 20, 2004 Share Posted April 20, 2004 Which engine does that car have? Is it the 2.2 or 2.5L? The Phase I 2.5L is prone to carbon build up. In my car, it caused a hesitation, or stumble when starting off under light throttle. I'm not sure from your post if this is 'exactly' what you are experiencing. Commuter Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 20, 2004 Author Share Posted April 20, 2004 it has ej22, and this has happened thru at least the past few full tanks. Today, it even did it at idle? Got me stumped, just want to research before I was to take it to the shop. Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 20, 2004 Share Posted April 20, 2004 have you changed the fuel filter ever? it sounds like a fuel delivery problem. have you checked all your fluid levels? has it been running a little warmer than usually? im just trying to see if there are any clues that might lead to something else? have you pulled the intake tube off the throttle body and inspected the butterfly flap for buildup? Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 20, 2004 Author Share Posted April 20, 2004 good thing to point out 'legacy25' I actually just purchased the car less than 1000 miles ago. I have drove 215,000 miles on my 93 impreza, and have had a ton of experience working on imprezas. Unfortunately I have never worked in an auto shop. I have been fortunate to have an impreza with high miles, and the message boards are to credit. I do want to change the fuel filter, but not til the weekend. The fuel filter definetely looks like it is stock, the arrows, the japanese symbols on it, but maybe not. Thanks,Max Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 20, 2004 Share Posted April 20, 2004 no problem, when u pull the old fuel filter look at the leftover gas in the filter, let it flow out the opposite way it normally does. because your letting the gas flow the opposite way you may see some containaments which would be a good indication of a dirty filter. let me know Quote Link to comment Share on other sites More sharing options...
Setright Posted April 21, 2004 Share Posted April 21, 2004 Get under the back seat and disconnect the fuel pump, start the engine and run until it stalls. That way the fuel pressure will have dropped and it wont squirt out when you undo the filter hoses! Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 21, 2004 Author Share Posted April 21, 2004 I will change the fuel filter on saturday. Last night it threw a CEL. It come on while driving, then it flashed, now it just stays on? I wonder what the minutes worth of flashing meant? Thanks for the comments. Max Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 21, 2004 Share Posted April 21, 2004 all you have to do is remove the fuel pump fuse, if you just remove the gas cap, it will elieve the pressure in the lines, and a minimal amount of fuel will come out the lines for a second or two. i wanted him to have fuel in the filter to check the gas etc. Quote Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 21, 2004 Share Posted April 21, 2004 I own a 99 Subaru Forester with a 2.5 manual. I was having a stumbling problem at take-off and I was also experiencing rough/skipping engine perfomance when I accelerated. I replaced the Fuel Filter last night and I also put an additive/clearner in the tank. It made a huge difference. The acceleration is much much smoother now. I would also like to point out that the fuel filter replacement was the easiest I have ever done. In all my previous experiences the filter has been under the car...and in the worst cases it was stuck between the tank and the chassis. I was delighted to see that the Japanese put the filter in an extremely accessible position under the hood. It even had a little "flip clamp" for easy and quick removal. The more I get to know this car the more I appreciate the user friendly design. American Carmakers go out of there way to insure that you need special tools and/or training to work on thier vehicles. Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 21, 2004 Share Posted April 21, 2004 i know, its cake to change the fuel filter Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 25, 2004 Author Share Posted April 25, 2004 Yesterday, before I was going to get a fuel filter, I went ahead and cleaned the TB with TB cleaner, then I cleaned the Mass Air Sensor, and the problem went away. Until today anyway, but it is not as intense. Oh well I am going to wait one more week (legacy2.5) for fuel filter and try to get the CEL to come on. Thanks for the comments. Max Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 25, 2004 Author Share Posted April 25, 2004 Yesterday, before I was going to get a fuel filter, I went ahead and cleaned the TB with TB cleaner, then I cleaned the Mass Air Sensor, and the problem went away. Until today anyway, but it is not as intense. Oh well I am going to wait one more week for fuel filter and try to get the CEL to come on. Thanks for the comments. Max Quote Link to comment Share on other sites More sharing options...
legacy2.5 Posted April 25, 2004 Share Posted April 25, 2004 thats cool. glad your car is running better. still change that fuel filter your car will thank you for it. luckily i am a tech. and can stay on top of my maintance. staying up on your maintance is ne of the best ways to keep your car runing well. i clean my throttle body about twice a year. have you ever done a fuel injector service??? or even added some cleaner to the fuel tank?? Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted April 26, 2004 Author Share Posted April 26, 2004 I don't know I just bought the car used. Don't know what the maintenance has been like. It come with aftermarket rims tires, and blue brake pads. So the previous owner was probably an enthusiast, and we usually take decent care of our cars. I wonder who makes blue brake pads? Max Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted May 2, 2004 Author Share Posted May 2, 2004 Finally CEL light came on flashing. I believe the flash means misfire, now it stays on steady. Got the code pulled and it flashed p0302- Cyl #2 misfire. I suppose I will start with spark plugs, wires. Thanks for the replys. Max Quote Link to comment Share on other sites More sharing options...
frag Posted May 2, 2004 Share Posted May 2, 2004 I read somewhere that the flashing CEL means the malfunction can damage the catalytic converter. A cylinder misfire sends raw gas into the cat. That can destroy it if it's left to go on. Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted May 10, 2004 Author Share Posted May 10, 2004 Today, I replaced the spark plugs. CYL 2 & 4 had a problem. The washer on the NGK's were not flat against the cyl head. One side was against the seat of the spark plug, and the opposite side of the washer wasup a few placeson the thread. Both 2 & 4 show carbon past the washer. Obviously this would likely be the problem. So I put new NGK's in, and I took the car for a spin. Wheew! No more hesiation. Then at the end of the day, it hesitates, and stumbles bad. especially with A/C on. So if we review, a couple weeks ago, I clean the TB and MAS... Problem goes away, good driving car. Until the end of the day. Today, I replace spark plugs... Problem goes away, good driving car. Until end of the day. Then the same stumble comes back. I will still say with a long time of driving soobs, this is not the normal hesitation. Something is wierd if the car seems great after fixing other parts then goes back to driving bad. Next is fuel filter just as Legacy25 advised. Any info is much obliged! Max Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted July 22, 2005 Author Share Posted July 22, 2005 Changed the fuel fliter, and reset the ECU car responds much better, however the hseitation is still there but, it is not as bad. This being said I have put about 100 miles on the car, but gradually getting worse. I have a question on oxygen sensors? I know there are 2 on the 98 OBS, but if I was going to replace one first with the problems I'm having, which one should I replace first? Front or Rear? I think front reads A/F mixture, and rear O2 sensor reads the cats servicability. Thanks MAX Quote Link to comment Share on other sites More sharing options...
Setright Posted July 22, 2005 Share Posted July 22, 2005 Yep, start by replacing the front one. ECU uses this info to trim mixture. See if you can get a three wire sensor. The extra wire is ground. Quote Link to comment Share on other sites More sharing options...
Impreza_WRX_STi Posted July 22, 2005 Author Share Posted July 22, 2005 Yeah I'll look for one thanks Quote Link to comment Share on other sites More sharing options...
99obw Posted July 22, 2005 Share Posted July 22, 2005 The front sensor is probably a four wire, which has the ground, the rear sensor is probably a three wire, which does not have the ground. Quote Link to comment Share on other sites More sharing options...
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