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Old 04-09-2002, 02:57 PM   #1
RallyNavvie
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Question Odd problem, bad fuel?

Recently my engine has started to do this wierd "hiccup" thing, mostly only noticeable below 2500 RPM and especially during idle. I'll start from the beginning.

I started noticing this after filling my car with 92 RON at my local station where I usually fill up. I've never had problems with gas there. While filling up I was maybe 25 short of a round dollar when the filler gun stopped so I slowly fed more in until it was a full dollar amount. That equated to maybe 1/6 of a gallon or so.

Right after starting I noticed at idle that the engine sputtered for a split-second shortly after which followed by my idle control motor regaining idle like it normally does, which is a little odd but it still works. I thought perhaps overfilling did something and I just needed to burn off some fuel seeing as the vapor control system is no longer running on my car since the Haltech really doesn't control it. I drove as usual for a few miled and didn't notice anything different in regular driving. At the first stoplight I didn't hear anything sputter and kept going. Then I had a quick loss of power at 55mph or so and so I pulled into the next gas station to monitor some things.

Here's what I notice during these "hiccups". The EGTs were pretty much normal. My A/F would dip only very slightly when it happened, then stay as it usual does on idle. The vac sits at 20 in/Hg while idling normally, goes to 18 right after the hiccup when the idle motor revs the engine slightly to regain control, then dips to 22 as the revs drop to idle again, then back to 20 so that seems like it's working okay and it isn't an injector issue. Tach bounces around when it happens, basically dipping 100-200 RPM each time it happens before it recovers. Injector duty cycle, TPS, volts, and almost all other things I can monitor with the Haltech were within normal parameters.

After checking all those things I kept driving and it didn't happen again for the 20 mile drive out and back home, and I let it idle before coming home for a couple minutes to see if it would hiccup but it did not. So I thought it was worked out. Today it seems to be even worse. I am also noticing the fuel pump (a Walbro) changes pitch just as the hiccup occurs. They are also occuring while I moved my car around in my driveway. The exhaust is popping a lot when it happens and there is a little bit of water in it, though likely just condensation in that big 3" exhaust. I pulled a plug just now and it's just got some black build-up on it that wipes off easily, likely because I'm still running on the rich side until I have a chance to better tune the maps.

Any ideas? Doesn't seem like injector or ignition issues. I am guessing that perhaps the fuel pump was damaged when I overpumped my tank, but how do I know for sure? I may take it and drive around for a little while and see if that makes it go away. I'm pretty sure this is not an issue with the Haltech since it's been working fine for 3 months. The only other factor is the weather. It has been in the 50s these past couple days and the warmest it has been prior is in the mid-40s. However the Haltech intake air temp correction map is smooth over the temps and doesn't seem to need any corrections.

I'm stumped

~Garrett
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Old 04-09-2002, 04:17 PM   #2
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Have you monitored your fuel pressure through all that? Sounds like a fuel pump may be culprit, like you said.
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Old 04-09-2002, 05:50 PM   #3
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I have pretty much the same exact conditions as you. I'm still not sure of the exact cause, but one thing I have noticed is one of my plug wires is gone, I have a new one on order to see if that fixes it.

I pulled the wires from the coil pack and one of the terminals had tons of oxidation on it, looking inside the boot and noticed that the connector was not round, but spread out some so it was barely making contact. (I think this is how I did my dyno run too )

so check you wires too, hopefully when I get mine in it will fix it. if not keep us posted if yours is something else as it does sound EXACTLY the same as my problem. (no haltech yet )

eli
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Old 04-09-2002, 06:57 PM   #4
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I don't have a fuel pressure gauge in the car so I can't really diagnose the fuel system much. The fuel pump noise could have something to do with the FPR sending it odd signals as the problem occurs.

I looked at my plug wires and they don't look terrible, but one is getting a little ugly. It was like that when we installed the Haltech and we fixed it up a little. I've been running it since with no problems. Don't see why this would just be happening now. The craziest thing is it wasn't happening before I went to this gas station to fill up and noticed the problem right after I started up after filling. It really leads me to believe it's a fuel problem, but I didn't know bad gas could cause problems like this.

Update: I drove it around the neighborhood today and it seems to be doing it more often and at almost all RPMs, though less at higher RPMs. Taking off from a stop sounds crazy, like vr-oo-ooo-ooo-ooom, stuttering like that really bad. Like I said, seems to be doing it less at higher RPMs, but the result is a bit more dramatic at higher RPMs. Haven't risked going into boost since I felt this because that would just be crazy. I added a bottle of dry gas to see if it would clean things up. I'll try again tomorrow.

Would over-pumping the gas hurt the fuel pump at all? I just don't see how the unit could get damaged like that. I was thinking misfire or ignition problems, but those are more likely on throttle tip-in. Would misfires happen at idle? Think I can limp this thing 20 miles to the guy who can help me identify the problem? It's just so crazy, I don't think I'm just going to be able to burn off this tank of gas like this

~Garrett
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Old 04-09-2002, 07:11 PM   #5
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I have a suggestion.

It may be your fuel filter, possibly. As they begin to go, you will notice somewhat of an erratic behavior in fuel pressure. This is what my friend told me, and he's a Subie tech, so you might want to look into it.

If you don't have a fuel pressure gauge, they're good for one thing, and thats to meter the life of your fuel filter.

I'm not sold on the fact over-filling will damage the pump. How many miles are on it? I've heard of Walbro's dying before, so it might be worth your time to pull it out and check it. You could have some dirt/debris caught in the filter right before the pump. Maybe someone maliciously put something in your tank to sabotage your car.

I'm just throwing ideas. Anyway, sorry Garret, hope you get it fixed soon....
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Old 04-09-2002, 07:56 PM   #6
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I actually got my fuel filter replaced just the other day, I honestly don't remember if it was happening before the filter replace or not, I did notice that I got a ton more power after the filter replace. still the stock pump for me. we need to get this figured out. wish my plug wires would arrive soon so I can see if that fixes it.

eli
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Old 04-10-2002, 04:01 AM   #7
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i have YET to see a fuel filter clog enough(not saying you didn't get horrid gas) to cause any kindof running problem. If it's any consilation the filters honda now uses are lifetime intank filters. They found that they rarely get dirty enough to cause any problems. So i REALLY doubt it's that. garret are you running a rising rate?? i'd say it's most likely a fuel pump starting to act funky.

jeremy
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Old 04-10-2002, 12:38 PM   #8
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Still using the stock FPR. I may disconnect the vac connection to it just to make sure it isn't a faulty FPR messing with the pump.

At this point I don't think the fuel filter is the problem. This seems too serious to be just the filter. I believe it to be either bad fuel, the fuel pump, or ignition problems. I'm still leaning more toward bad gas (hoping, moreover) since the catalyst was the fill-up at the gas station. The fuel pump is my next culprit. It has about 30k miles on it, but they shouldn't go out that fast should they? Ignition could cause this problem, but it would be more pronounced during throttle tip-in and really shouldn't be happening at idle when there is next to no load on the ignition system.

However the Haltech will allow me to turn the fuel pump on and keep it running, I'm just not sure how. If I turn the pump on to listen to it for odd sounds the fuel it's pumping will just go through the rails and right back into the tank won't it? I can also use the pump to get rid of the gas rather than burn it off or syphon it. Just have to figure out how to get that to work.

So now the question: is it safe to drive somewhere if the pump sounds fine? If it is the ignition I can keep low loads on it or just pinch the terminal onto the post to make sure it's getting good contact. Why do I get stuck with all these crazy problems

~Garrett
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Old 04-10-2002, 02:04 PM   #9
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Since I am a fan of Occum's Razor, the thing I would look at is your gas. During the winter, most fuel companies use a blend of fuel that burns cleaner than in the summer. They do this to try and keep cities that have a lot of polution a little cleaner. March/April is usually when they switch back to normal "summer" fuel.

Since you are running the Haltech, you may need to alter you base map just a little for the different fuels. What you maybe expereincing is the Haltech "learning" the new fuel, if it has that ability.

totally just a random thought.

jeff
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Old 04-10-2002, 02:37 PM   #10
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I was thinking about the difference between winter/summer gas. It's usually only a matter or leaning or enrichment of the fuel, which I can do with the fuel trim knob. Changing the fuel trim doesn't seem to have an effect on the problem, so I'm not really thinking it's a different fuel. Besides, the last time the station had filled its 92 RON tank was March 23rd so it would have still been winter gas. I do have to take a gas sample back into the station for testing, results come back Monday. I told them about the Dry Gas I added to it but they can probably test around that with the equipment they have.

Anyway, where do I get another Walbro pump if I need one? I see they only run $125 or most applications and since I didn't do the install on this pump I'm not sure which one to use. Do I just get the high-flow Walbro for the Supra TT? Where's the best place to buy from?

~Garrett
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Old 04-10-2002, 04:24 PM   #11
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Garret, check this thread and you'll find everything you need for your a Walbro:

http://www.i-club.com/forums/showthr...lbro+fuel+pump


Blaster found the right stuff for our Subies.


Graham
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Old 04-10-2002, 09:42 PM   #12
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Had a very similar problem to this on my 02 WRX after the last fillup... at 4000 rpm the car buck like a mofo.... hoping it's just a fuel problem!
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Old 04-10-2002, 10:08 PM   #13
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wow. its so strange because i got that exact problem on my RS. it started last time when i filled up which was a couple days ago. here is the thing, my RS is stock engine wise. for mods all i have is intake, exhaust, afc, and itc. i zero'd out the afc and itc and still got the noise. i think its a possiblilty they put something in the gas the last week or so.
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Old 04-10-2002, 10:29 PM   #14
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Hope it works out well!
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Old 04-11-2002, 02:27 AM   #15
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Another possibility is that in the process of (over) filling your tank, you may have forced fuel into the charcoal canister. (which is connected to the vent hose coming from the fuel tank as required by the EPA to prevent the escape of gasoline volatiles). If the canister is in fact full of fuel, it may prevent your gas tank from venting properly as you use fuel. Generally fuel pumps change pitch when they are starved for fuel (pumping air).

Good Luck !

Dave
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Old 04-11-2002, 02:34 AM   #16
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Quote:
Originally posted by Suebee2
Another possibility is that in the process of (over) filling your tank, you may have forced fuel into the charcoal canister. (which is connected to the vent hose coming from the fuel tank as required by the EPA to prevent the escape of gasoline volatiles). If the canister is in fact full of fuel, it may prevent your gas tank from venting properly as you use fuel. Generally fuel pumps change pitch when they are starved for fuel (pumping air).

Good Luck !

Dave
FYI tanks are made to hold at least 10% more by goverment standards to allow for the expansion and contraction of the fuel. I just thought of something however....since the EVAP system only starts to run when it's warm out i wonder if your hiccup was a sudden burst of moisture from the EVAP canister. How long have you been running your haltech garret??

Jeremy
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Old 04-11-2002, 11:23 AM   #17
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Bad news

We drained the car of almost all of its fuel. Although tedious we disconnected the fuel line going into the filter and led that into a fuel tank and used the fuel pump to get rid of all the fuel. I was only able to pull maybe 9 gallons that way and with only 50 miles on that tank of gas there must have still been 3 gallons or so left in there. So we put 5 gallons of good gas in the tank and tried that: problem is still occuring.

So since we seem to have ruled out bad gas I next went to the ignition system. The problem got progressively worse as I drove the car to the shop. We pulled the plug wires, cleaned the contact a little, greased them, and put them back on. Again, no change in behavior. Unless a plug wire is completely broken somewhere the wires look fine. I would have to test them for resistance to make sure. Still, new wires from the dealer are only about $50.

New theory: valve float. There has been a lot of this occuring in the EJ25. Supposedly you can notice this problem if you take off the exhaust manifold. I haven't gone that far yet.

As far as the charcoal canister is concerned it is completely useless for now. There is nothing that uses it to purge fuel vapors back into the fuel system so it really isn't an issue. I had no idea what that thing was when I saw it though. I guess I'd never noticed that thing before.

The Haltech has been on the car and running for 3 months. I really don't think this is an issue with the Haltech or its maps. I think this is some mechanical problem or system autonomous of the Haltech.

~Garrett
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Old 04-11-2002, 11:37 AM   #18
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I wouldn't think this has anything to do with the ECU since the same thing is happening to me (although only at idle, not when I'm driving), another person with a non-turbo rs said the same thing is happening to them, wish I woulda had this looked at before my warranty ran up

new plug wire for me tomorrow, I'll keep ya posted if that fixes mine.

eli
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Old 04-11-2002, 07:53 PM   #19
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ok. i've ruled out a couple things.
can't be gas. i filled up with 92 octane still does it.
plug wires are fine.

one last thing to check. plugs. i'll check tomorrow and report back.
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Old 04-11-2002, 10:24 PM   #20
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Might take more than 1 tank to eliminate possible bad fuel.
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Old 04-12-2002, 10:58 AM   #21
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Well I can't afford to run like this until it purges the system of bad gas. The drive is so rough now that I was fanning the clutch just to keep the drivetrain components safe. I got most of it out and let it idle for a couple minutes and it didn't seem to happen less often or anything. The only way to completely drain the tank is to take it off and empty it. If the results from the gas sample come back bad then the gas company (Marathon) will reimburse me for any charges incurred, in which case I'll bring it to the dealer to get the tank drained.

So the car is dead for the moment and I'm not quite sure what to do with it. I'm getting a trailer to get it back home, even though I'd rather leave it where it is since it's right outside a shop, but it could still be broken into and stuff stolen out of it so it can't really stay there. I need to buy an old beater Subaru for when stuff like this happens.

~Garrett
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Old 04-12-2002, 12:04 PM   #22
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I hope you have found the catalyst Garret (bad gas). I don't think thats MY number one reason for this, but I can be wrong. Hopefully its something as simple as bad fuel.

Keep us updated.

Graham
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Old 04-12-2002, 09:03 PM   #23
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Well the car is in a safe place now and with someone who is far more qualified to figure out what is wrong with the car; the guy who helped me install my Haltech, our local Subaru guru and all around nice guy. I don't know how I'm going to repay him if he fixes this. Maybe he'll accept my first born

~Garrett
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Old 04-13-2002, 01:59 AM   #24
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did you switch from MAF to MAP with the Haltech?
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Old 04-13-2002, 03:13 AM   #25
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Yeah, that was one of the big selling points of the Haltech for me was to get rid of the MAF. There's a 3-bar MAP sensor on the right strut tower now. Why?

~G
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