Feels like a spark cut-off, or maybe fuel cut-off... i dunno

TheSubaruJunkie · Post by **TheSubaruJunkie** » Fri Nov 05, 2004 2:09 am

Yesterday morning i woke up, and drove my car home from a friends house. Its a 30mile drive, and the car drove great. No problems. Mind you, it was raining and its one of our 1st rainfalls here in California.

I get home and park it, then I go out later in the afternoon to head to my parents house. As soon as I pull out of the driveway and head down the street I feel the car bucking and backfire, so i lay off the gas and it goes back to normal. No stalling. So I drive off, and feather the throttle.

Im able to drive the car just fine, as long as Im feathering the throttle. If i give it too much gas it cuts out and bucks, backfires and doesnt want to drive. Seems to only do it if the engine is under load, or hard acceleration. At a stand still I can rev the engine to 6k no problem. If Im in gear and lightly accelerate it will go to 6k no problem, but heaven forbid if I want to actaully get up and go... any hard acceleration and the car just cuts out on me.

I spoke with Ryan and he suggested my fuel filter. Once i thought about it, it made sence so I bought a new filter. The car drove better for about 1/4 mile on its test drive, but the problem came back. As soon as I got home I swapped the Diamond coilpack for the stock one to see if it was the coilpack. On that test drive the car was able to accelerate from 1st to 2nd to 3rd no problem... but as soon as I shifted to 4th the problem re-appeared and now its back no matter what.

Im kinda stumped. Hardy and Scott say to check the plugs (i havent yet) but they're new, no more than 2000miles.

I find it odd that this problem would appear out of the blue, and wonder if maybe its related to the weather.

Anyone have anything like this happen before?

-Brian

dirty kru · Post by **dirty kru** » Fri Nov 05, 2004 2:18 am

i had a subaru come into work with a similar problem

we found that as the fuel in the tank got low it started picking up crap and blocking the filter.
the solution...
the 1/4 line on the petrol guage is the lowest the petrol could be..

TheSubaruJunkie · Post by **TheSubaruJunkie** » Fri Nov 05, 2004 2:19 am

yeah, thats what im going to do next... fill the tank to full.

-Brian

vrg3 · Post by **vrg3** » Fri Nov 05, 2004 3:28 am

You don't have a Check Engine light, do you?

Does it start cutting out almost exactly when manifold pressure reaches atmospheric, by any chance? Because that's what happens when the ECU throws a trouble code for pressure sensing or boost control. On my car it also does it if I connect the test mode connectors after the engine is running.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Fri Nov 05, 2004 5:10 am

no CEL at all. I dont know where to check my ECU for codes, do I gotta remove the panel under my steering wheel to get to the ECU light?

I have no idea if its happening when the manifold reaches at. pressure. Just when the car is under heavy load.

-Brian

vrg3 · Post by **vrg3** » Fri Nov 05, 2004 5:29 am

You don't have a boost gauge?

Does the CEL turn on when you turn the ignition on but before you start the engine? I just want to make sure the bulb isn't burnt out.

If it's not some kind of ECU issue, I agree with Hardy and Scott that it sounds like some kind of spark issue. The higher the load, the harder it is to make the spark happen.

Are all the ignition leads seated properly? When you push the terminal onto the plug you should feel/hear it click when the contact snaps on.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Fri Nov 05, 2004 5:43 am

the ignition leads... is that the cable leading from the coilpack? Cause the clip is broken and i have it zip tied together... but its sure to make contact and has been that way since i installed my 1st diamond.

I'd have to re-check to see if the CEL light comes on with the ignition... i dont think ive ever seen it.

-Brian

Lunatech · Post by **Lunatech** » Fri Nov 05, 2004 9:04 am

Believe it or not, I had this exact same thing happen to my car Monday. With the possible exception of I had smoke during coughing and sputtering.

I went through the usual train of thought: plugs, wires, fuel filter, air filter, weather, debris in thank, coil, ecu, vacuum leak, head gasket, and just plain old bad gas.

Checked all the plug wires to make sure they were all attached properly. They were, no difference,

Next I pulled the air filter, inspected it, a little dirty but not bad. Tried driving around a little without it, no difference.

I filled the tank, after I used up just about as much gas as I was comfortable with and put in a bottle of gas treatment, no difference.

Finally on Tuesday the rain stopped and I got out there and pulled the plugs. Number 1 was fouled pretty badly with oil, the rest looked fine. So I cleaned them, put them back in and went for a test run. All is back to normal for now.

Now I know my engine is quite worn out. I did the head gaskets last summer and the number one piston is very loose in the cylinder. I do have another engine that is in the works I just hope this one lasts long enough for me to finish it. Even as worn out as it is it still runs strong and is reliable, for now.

I hope this helps.

Robert.

J-MoNeY · Post by **J-MoNeY** » Fri Nov 05, 2004 9:14 am

MAFS.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Fri Nov 05, 2004 1:06 pm

If MAFS stands for Mass AirFlow Sensor, i hope your wrong. That sounds like an expensive part.

I think im going to try what Robert suggested. I havent been able to see if there's black smoke through the exhaust, but with the way its backfiring I could only imagine huge plumes of the stuff.

I just hope the weather clears up so I can do some work on it.

-Brian

vrg3 · Post by **vrg3** » Fri Nov 05, 2004 2:19 pm

Brian - The ignition leads are the spark plug wires.

It doesn't sound like a MAF problem to me, but anything's possible... You can try cleaning the sensor before replacing it.

professor · Post by **professor** » Fri Nov 05, 2004 3:45 pm

even if the plugs are new, pull them right after a coughing episode. That way, you can hone in on the cylinder that is responsible. If a plug looks fouled, suspect that wire.

Your symptoms sound exactly like you are losing spark on one cylinder, the car will often run fine but when you goose it, there is enough amperage in the wires to jump a gap somewhere and ground out your spark, or to heat your wires enough to give big resistance if one wire has gone bad.

Try running it at night or in a dark garage with someone giving it some gas, listen for the snap and the light of an errant spark.

If you do see one bad plug, clean it up, remove that wire and clean it up and seal it back on with dielectric grease. If no go after that then you may have a coil pack problem, or the wire may have a bad spot

THAWA · Post by **THAWA** » Fri Nov 05, 2004 5:01 pm

brian, lets exchange plug wires sometime. I have a feeling that may be the problem.

J-MoNeY · Post by **J-MoNeY** » Fri Nov 05, 2004 7:11 pm

vrg3 wrote:Brian - The ignition leads are the spark plug wires.

It doesn't sound like a MAF problem to me, but anything's possible... You can try cleaning the sensor before replacing it.

When I jerryrigged my intake , the turbulent air comming into my Mass Air Flow Sensor was fubared. I recall having this exact same problem. I suggest this just from personal experience.

vrg3 · Post by **vrg3** » Fri Nov 05, 2004 7:55 pm

Oh, yeah, I hadn't considered the possibility that he'd modified the intake.

THAWA · Post by **THAWA** » Fri Nov 05, 2004 10:31 pm

he hasn't, its possible it could be a maf problem, but more likely it's a spark issue though. plus plug wires are cheaper than mafs

TheSubaruJunkie · Post by **TheSubaruJunkie** » Sat Nov 06, 2004 2:58 am

Yeah they are. But not by much. Arent EJ22T wires kinda spendy?

I'll have to check it tomorrow, too late to do it now.

-Brian

vrg3 · Post by **vrg3** » Sat Nov 06, 2004 3:55 am

EJ22T wires are the same as EJ22 wires. They're not too expensive. You could even get Magnecors for like $65 and never need to buy another set of wires.

It doesn't matter which is more expensive. You need to fix your problem! Don't let fear that something might be wrong keep you from testing that thing.

If the wires are fairly new, though, then it might just be that one isn't properly seated on the plug. Just go unplug the wires and plug them back in properly and see if that does anything. It'll take 5 minutes.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Sat Nov 06, 2004 4:25 am

Okay, im going to go buy new wires.

Sure wish my garage was cleaned so I could work in it

-Brian

vrg3 · Post by **vrg3** » Sat Nov 06, 2004 5:32 am

No, don't buy new wires yet! First check that the ones you have already are properly installed.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Sat Nov 06, 2004 5:47 am

checked them yesterday and they were. I cant see if they're arching or anything cause the car runs just fine at idle or at a stand still, i'd have to have the car in motion to create the symptoms and i dont know if Hardy wants to be under the hood while Im screamin down the road.... unless he does

Tomorrow I'll run to the store for new plugs. Right now im trying the ECU reset.

-Brian

vrg3 · Post by **vrg3** » Sat Nov 06, 2004 5:51 am

Oh. No scorching on the contacts or anything?

Yeah, you can't really load the engine in the garage... You can put a little bit of load on it by using the brakes against the clutch, but that's hard on the clutch.

mikec · Post by **mikec** » Sat Nov 06, 2004 6:25 am

Have you switched them for a known good pair? That would be the inexpensive way of getting new ones, wouldn't it?

Unless you think they're old, in which case its a useful maintenance item.

TheSubaruJunkie · Post by **TheSubaruJunkie** » Sat Nov 06, 2004 6:31 am

I think they're pretty old. I was going to replace them anyway.

-Brian

mikec · Post by **mikec** » Sat Nov 06, 2004 6:37 am

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Feels like a spark cut-off, or maybe fuel cut-off... i dunno

Feels like a spark cut-off, or maybe fuel cut-off... i dunno