What would my car be doing if my spark plugs needed replacing?

[GraysonK]

That pretty much sums it up.  When I go up a hill or something, the car all of sudden starts kind of popping...not quite as dramatic, but like when you forget to take the car out of gear then take your foot of the clutch.  No problems starting, just kind of stutters I guess.  I think it's the spark plugs that need replacing.  Does that sound about right? 

[Pacu]

that or fuel filter...maybe vapor lock?

get a spark plug brush and give em a good cleanin or replacing..mind the firing order then go from there. Ifin one is mis-firing it causes a hit then lurch feeling.

[Mr. Whippy]

A LOT of possibilities.  Depends on a lot of things: Points and condenser or electronic ignition?  How many miles?  Is the check engine light on?  What does the exhaust look like (white puffs, black puffs, no puffs, etc)?  When was the fuel filter last changed?  Any difference in the rain or dry?

The list of possible causes is really long.  More info needed.

[Zack]

Could be a number of things.  Start with the fuel filter, could also be an O2 sensor.  What kind of car and how many miles?

[RaptorMan]

What kind of car?

[GraysonK]

A LOT of possibilities.  Depends on a lot of things: Points and condenser or electronic ignition?  How many miles?  Is the check engine light on?  What does the exhaust look like (white puffs, black puffs, no puffs, etc)?  When was the fuel filter last changed?  Any difference in the rain or dry?

The list of possible causes is really long.  More info needed.

Ok, I have a 2002 Subaru Forester.  It has 66,000 miles.  Spark plugs have never been changed, that I know of (I bought it when it had like 50,000 + miles on it).  There's no discolored exhaust that I know of.  It started doing this in earnest after the last time I put gas in the car which was 2 weeks ago.  It doesn't have any problems idling or starting.  Does that help?

[jim guy]

bad gas? Put a bottle of Heat in it, if its got water in it the Heat will help

[Zack]

I say change the fuel filter and run some lucas oil gas treatment in it.  It could be an exhaust leak as well, but lets try the cheapest alternatives first.

[Pacu]

sometimes if the petrol station tank is low and you fill up all the water/crap laying low is pumped into your auto.

[jim guy]

yeah changing the filter would be a good idea, if it has one. I dont know about subarus,  but most newer chrysler products have the filter in the tank.

[jzmtl]

Only uphill? Or does it too when accelerate hard on level ground? If only uphill could be water swooshing to back of tank and picked up by the fuel pickup tube. Like said try a bottle of gas line antifreeze (or pure ethanol/methanol if you have any around, that's what the antifreeze/heet is).

[GraysonK]

Only uphill? Or does it too when accelerate hard on level ground? If only uphill could be water swooshing to back of tank and picked up by the fuel pickup tube. Like said try a bottle of gas line antifreeze (or pure ethanol/methanol if you have any around, that's what the antifreeze/heet is).

It does the same thing on level ground too.  If I put something like the heet stuff in my tank, if there isn't water it won't hurt anything will it?  never had to do this stuff before so I'm less than a rank amateur. 

[EM745]

Reminds me of what happened to my parents' '86 Camry years ago: Bad gas --> blown fuel pump!

The symptoms were similar to what you describe, and began soon after a refill. The car started and idled just fine, it even revved ok while in park (it was an automatic). But when in gear and under load (accelerating, going uphill), it bucked and sputtered like crazy.

Mechanics checked the small stuff first, and sure enough, the fuel filter showed signs of dirty gas. It was replaced, but the problem persisted. They then checked other things like engine timing, all the sparking hardware, sensors, throttle body, fuel system (they did a thorough cleaning)... they even checked for blockage in the cat converter. They also checked the fuel pressure, but only at idle (park) at first. Fuel pressure was within spec. Nothing worked. They were stumped. The car was in and out of the service bay for a few days until it dawned on them to check the fuel pressure while in drive. That's when they noticed that the pressure actually dropped when in drive (it should go up). A new fuel pump solved the problem (quite an expensive repair, IIRC). Seems the bad gas all but clogged up the filter, overstressing the pump into giving up the ghost.

After checking out the "easy" stuff, I'd have the fuel pump's pressure thoroughly checked, just in case.

My 2¢.

[jzmtl]

It does the same thing on level ground too.  If I put something like the heet stuff in my tank, if there isn't water it won't hurt anything will it?  never had to do this stuff before so I'm less than a rank amateur. 

Nope it'll just mix with gas (and any water) and get burned. I still think it's gas thou if it started right after you filled it up, try a bottle of heet and see what happens.

You didn't happen to put diesel in did you? 

[GraysonK]

It does the same thing on level ground too.  If I put something like the heet stuff in my tank, if there isn't water it won't hurt anything will it?  never had to do this stuff before so I'm less than a rank amateur. 

Nope it'll just mix with gas (and any water) and get burned. I still think it's gas thou if it started right after you filled it up, try a bottle of heet and see what happens.

You didn't happen to put diesel in did you? 

No, I didn't put diesal in it.  I'm gonna take it to advanced auto tomorrow and have them put the computer to it and see if that shows anything.  If not, I'll try the heet stuff.  Thanks everyone!

[Benner]

Kelly, all of those have been great suggestions, but personally I'd be starting with what you queried - the spark plugs.  I had the exact same issue with a Micra I had and it was one of the spark plugs causing a misfire (which is what sounds to be your problem).  Considering how easy plugs are to change and how cheap they are, and they fact they have never been changed, that would be the first thing I'd personally be starting with.

[Grant Lamontagne]

I'd suggest the same thing as those above before going to a garage.  I'd also suggest getting yourself a Chilton or Haynes type manual for your car as well, as it'll walk you through basic mechanical procedures like changing plugs, as well as giving you the proper info for things like proper gap size.  While I wouldn't suggest getting the top of the line platinum tipped, zirconium encrusted, warp drive enabled plugs, I would suggest getting a decent set- spend a bit of money, but don't go over the top!  You can also look at changing the wires, and again, get some good ones, but don't bother with the super expensive ones.

Look at fuel additives and see what is formulated for the specific problems you are having, and consider a new fuel filter as well.  I suggest doing all of this because each of these things can and will help your car, even if they don't solve your problems, and they are all something that even a novice can do with a few hand tools and the afore mentioned manuals for guidance.  If your problem is solved, great, if not, then you can consider talking to a mechanic.  If at that point you do talk to a mechanic, you will at least sound like you have a good idea of what you are doing, and you are less likely to be taken for a ride if the mechanic you talk to is not on the level.

This isn't a shot at mechanics out there- most of them are good, but there are enough unscrupulous ones out there that I always recommend a certain amount of caution when dealing with them.

Def

[Mr. Whippy]

I would start with the theory it was bad gas (water in gas).  Heet is basically methanol, so it emulsifies the water into the gas.  Water in gas would most definitely give you a misfire on load.

It will not be an instant fix.  You will likely have to treat a couple tanksful since whatever water is in there is only diluted when you add more gas (ie full to half tank and refill again only dilutes the water to half its previous concentration, and dilutes the HEET too).

It could be a combination as well. (ie bad gas led to misfiring which led to damaged plugs) Until this straightens out, I would drive gently (ie avoid heavy acceleration).

Lots of good comments here, btw.

[jzmtl]

If you have the wrench it's quick enough to take out a plug and see if it's good.

[thebullfrog]

Start with the spark plugs. They're a bitch and a half to get at on that engine though. But it's the easiest/cheapest fix, and a good idea to do regardless. May as well change the wires too, it won't cost much more and they're already half off to do the plugs, so why not right? If that doesn't do it, then attack the fuel filter, I'm 99% sure Suby puts the filter outside the tank. Bad gas is a possibility however, so some Heet and careful driving (don't stomp on the gas) is a good idea as well. But the plugs are absolutely where I would start, as I've had those exact symptoms with destroyed plugs, and believe me I've destroyed a lot of plugs (I'd have a tendency to run too much boost and melt the things lol)

[NutSAK]

I agree w/Nate, it could be MANY things.  I don't think plug wires have been mentioned as one of the many possibilities.

[thebullfrog]

I agree w/Nate, it could be MANY things.  I don't think plug wires have been mentioned as one of the many possibilities.

I did lol

[Whoey]

as did Grant...

I keep seeing the title of this thread and wondering how Kelly's car plans to change her spark plugs... I need to sleep more apparently...

[GraysonK]

as did Grant...

I keep seeing the title of this thread and wondering how Kelly's car plans to change her spark plugs... I need to sleep more apparently...

 

[thebullfrog]

Subaru's are pretty loaded with features these days. Active Differential All Wheel Drive Systems, Navigation, and the patented S.A.H.S.P.C.S. or Subaru Automated Human Spark Plug Changing System. It's very trick, and an expensive option, but well worth it.

[Whoey]

as much as Kelly likes fancy tech toys, I'm pretty sure Kim's the only one she'd let under her hood to change her sparkplugs... 

[Mike, Lord of the Spammers!]

as much as Kelly likes fancy tech toys, I'm pretty sure Kim's the only one she'd let under her hood to change her sparkplugs... 

[thebullfrog]

 

[GraysonK]

as much as Kelly likes fancy tech toys, I'm pretty sure Kim's the only one she'd let under her hood to change her sparkplugs... 

You're right about that! 

[GraysonK]

Ok, so it's not the alternator (thank goodness) and I took it to advanced auto and they put that computer thing on it.  Computer thing says that i've got a misfire in 3 out of 4 cylinders...they are convinced it's the spark plugs.  Ok, so I got the plugs and the wires, my friend came over to show me how to change them and guess what...apparently you need to be able to dislocate your shoulder or have go go gadget arms to get to the darn things.  My friend is bringing over some tools on Sun morning to take some stuff out so she can reach the plugs.  Wow...subarus are good but apparently a b*tch to work on.