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| Need some fuel system diagnostic help; code P0420, trouble filling up, engine surge at idle | |
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| Tweet Topic Started: Nov 2 2012, 12:29 PM (629 Views) | |
| adt0039 | Nov 2 2012, 12:29 PM Post #1 |
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New Member
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Hi all! I recently got my (new to me) 1997, 1.0L, 5 speed on the road after discovering/repairing a damaged woodruff key journal under the crankshaft timing sprocket, and now I'd like some help diagnosing some new problems. I'm not sure how/if any of these symptoms are related, and I hate to speculate, so I'll describe them all and maybe y'all can help me connect the dots with some diagnostic ideas: 1) Immediately noticed the engine idling up and down, but drivable, so I took it for a test drive. 2) towards the end of my test drive, the car began humming from behind and to the left of the driver's seat. I got out and noticed the hum was close to the gas tank. 3) I then opened the gas cap, which was noticeably difficult to unscrew, and it hissed when I finally got it to break loose. 4) Drove it to the gas station, now the humming was in sync with the engine idling up. The higher the revs, the the louder the hum, and at the slowest revs, no hum at all. 5) Tried to put some gas in, and the pump immediately shut off on the lowest auto setting, so I put in a few gallons by squeezing the lowest manual setting. 6) Drove around still humming in sync with the revs, and in hopes that maybe that particular gas pump sensor was malfunctioning, I tried another station. Again, the lowest auto setting shut me off immediately, but I was able to put in a couple more gallons with the slowest manual squeeze. 7) I drove it to a couple gigs, and somewhere, somehow along the way, the humming stopped (don't remember exactly when) and at some point on the highway, the Service Engine Light popped on, code P0420. Can y'all help me out with some diagnostic ideas? Thanks! |
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| Stiffchezze | Nov 2 2012, 01:08 PM Post #2 |
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Sir Metrologist
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Long story short, P0420 usually means your cat is dead. Other than the light, it should not affect the engine at all. Also, Our little cars are hard to put gas in. ![]() No lie. The pumps at the gas stations are designed to fill a 75 gal SUV tank in under 5 min. With our little 10 gal tanks that usually only need 8 or so gal, they overflow quickly. Just take your time and go slow. It's a good thing we fill up so few times! ![]() From what I remember from your previous threads, this guy has been sitting for a little while. He is going to do weird things and make weird sounds for a little while. The hiss at the gas cap is normal.
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| Old Man | Nov 2 2012, 03:06 PM Post #3 |
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I have never had a problem with slow filling of the gas tank. --- Yes, the pressure coming out of the tank when you release the cap is normal. Slow filling is an indication that the small vent tube that is located beside the big fill tube is plugged. Therefore when you put gas in, the gas has to trickle into the tank letting air come up in the fill tube instead of the vent tube.
Edited by Old Man, Nov 2 2012, 03:07 PM.
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| mwebb | Nov 2 2012, 11:33 PM Post #4 |
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FOG
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see if leaving the fuel cap a half turn loose solves the surgeing if yes the evap vent valve is stuck closed or the evap vent valve filter is clogged sometimes spiders make nests is the opening and clogg it up the P0420 and the surgeing may be related to overpressure in the fuel system fix that first |
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| adt0039 | Nov 6 2012, 12:25 AM Post #5 |
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New Member
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Drove about 40 miles with the gas cap loose, no dice - surging continued... Thanks for the replies, not sure if the surging and P0420 are related, but I'm thinking I'm going to have to diagnose them separately. Luckily, my inspection's not up until April, but I'd still like to get that "Service Engine" light turned off sooner rather than later. I'll prolly start with checking the voltage output on the downstream O2 sensor first. Any ideas on how to start trying to diagnose the surging problem? |
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From what I remember from your previous threads, this guy has been sitting for a little while. He is going to do weird things and make weird sounds for a little while. The hiss at the gas cap is normal.

3:18 AM Jul 11