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Discussion Starter · #1 ·
Finally got my subie on the road. Most the time it drives fine but occasionally it has a weird stumble. The worst is parked facing up a hill then trying to accelerate. It will cough and stumble for a while but usually comes back to life. Sometimes it does it on more flat but is much more likely to do it under heavier acceleration. A few times it has completely stalled. I sit and crank it for 30-40 seconds and it starts to catch and fires back up. It really feels like the Gforce of acceleration is a main cause and facing uphill seems to amplify this. Now unfortunately this car is a basket case and some backwoods engineers tried to turn it into a race car. It has a fuel cell in the trunk with an external pump and everything that was done to it is ghetto. I first suspected the fuel cell or pump but it does this with a full tank and the pump seems to run strong. The pump is getting 13.3 volts. It dropped to about 11 for a second when the rad fan came on but bounced right back. I am going to be getting a stock tank, pump and sending unit soon to replace it.
I have checked and cleaned all the grounds in the engine bay and added one from the batt to the engine to the chassis. I have wiggled all the wires and hoses and everything I can think of that could allow g forces to effect the engine and don't see any problems. There is a lot that was poorly done on the car so I think I will just have to keep going through it but I thought it might be worth posting in case this was a known and or common problem that others had experienced before.
 

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'97 BrightonRS '93 Impreza FWD
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My first thought was the fuel pump. After explaining "ghett-astrope" I feel that way even more lol.

Is is auto or 5-speed?
 

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'97 BrightonRS '93 Impreza FWD
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Haha no. Clutch is fully out when it happens. Deff missing fuel or spark.
It is possible for the car to 'buck' even with the clutch engaged... Otherwise I would start looking at the battery, plugs, wires, coil, and checking for vacuum leaks... If your sure it has nothing to do with the fuel system.
 

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Discussion Starter · #7 ·
It is possible for the car to 'buck' even with the clutch engaged... Otherwise I would start looking at the battery, plugs, wires, coil, and checking for vacuum leaks... If your sure it has nothing to do with the fuel system.
Ok yeah I get you. It's deff not just bucking, it's an actual loss of power.
There are a couple broken bolts on the intake mani that I need to fix but wouldn't intake leaks show as a constant problem?
This went completely away for days then tonight came back and it was still intermittent. I'm not getting the feeling of something like a vacuum leak but more likely a loose wire or something getting tossed around, sometimes connecting other times not.
 

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'97 BrightonRS '93 Impreza FWD
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Ok yeah I get you. It's deff not just bucking, it's an actual loss of power.
There are a couple broken bolts on the intake mani that I need to fix but wouldn't intake leaks show as a constant problem?
This went completely away for days then tonight came back and it was still intermittent. I'm not getting the feeling of something like a vacuum leak but more likely a loose wire or something getting tossed around, sometimes connecting other times not.
Are the broken bolts the ones that hold the intake manifold to the heads? I would start there if I were you... Vacuum leaks can cause a plethora of ridiculous issues.
 

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Discussion Starter · #10 ·
So I got my 0BD2 adapter and caught it in the act.
For whatever reason the car is going dead rich when it happens. This eliminates a lot of my theories like the fuel pump cutting out or sucking air at the pickup. I also really doubt intake leaks. It will be a while before I can fix the broken studs but it idles great and runs great most the time. I actually had to up the idle a little when I got it. I also don't understand how an intake leak could seriously throw off a MAP car other than raising idle. I am used to my AFM MR2 and know that EFI system like the back of my hand. I also know intake leaks will effect AFRs on an AFM and MAF motor. If there is something I am missing about the map motor let me know. I am still in the process of learning this EFI.
Anyway for some reason it's reading dead rich. The WB and the NB 02 both agree so it appears they are functioning well. I can't find anything else in the tables that explains why It's randomly choosing to dump fuel on accel or most commonly starting from a stop facing uphill.

It has been running great the last couple days but there is a stop sign on a hill where I can get it to do this all the time even when it seems to be running otherwise fine.
Any ideas?

 

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Discussion Starter · #11 ·
Oh yeah forgot the details on the spreadsheet.

at second 520 I was sitting still at the stop sign off the gas. At 525 I step on the gas and start to accelerate. At 532 the AFRs go dead rich and the car starts to stumble. At 548 the AFRs return to normal and so does driveability.
 

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Discussion Starter · #12 ·
I'm surprised at the lack of input. Does no one else use OBD2 scanners? No one can tell me if anything jumps out in the logs?

One thing that jumped out at me last night is the pull at 25% throttle had a map reading of about 10 where the pull at 100% throttle had a map reading of about 11. I went back to logs where the problem wasn't present and at 30% throttle only saw a map reading of 6. It was under less load as well though.

Do those MAP numbers seem about right?
 
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