Spark Plug wires good method for testing out piston firing...?

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Ill explain what my problem is first.

When coming to stops my car will sound like its stalling but never does. I usually put it into neutral to calm it down when sitting at the red light or wherever

When puting the car in gear after a stop it will sound like stalling again until i give it enough gas to get it movin, then it sounds fine once im going.

The only time it seems to stall is when the car has been off for a few hours then I start it and dont give it enough time to warm up and take off, as soon as I accelerate after the first or second stop it will most likely stall out.

Now I had recently just changed my spark plugs and wires. When I did that someone told me to pull out each wire(only 1 out each time) while the engine is running to listen for a difference in sound(engine reving up then down). When i did that each wire i pulled out made a noticeable difference in sound, except for the 6th piston which made no difference in sound wheather it was in or out. Also the wires were sparking fine when puting close to engine block as i was told to check that as well.

My question is. Is that a good method of testing out my pistons firing and if so is that the problem or could it also be somthing else ???

Any ideas is most appreciated, thanks.

oh car is a 91 pontiac sunbird

posted by  Rad1

ya today was an interesting day.

My car now stalls every time i stop, putting in neutral doesnt even help anymore. I have to keep the engine about 1000 rpm to keep it goin when in neutral.

would a change in temperature outside have effects on an engine cause today was pretty warm 4 Celcius. Since I had the car ive been driving in temp around -2 celcius the highest ??

whatever the case im probably gona bring her in for a diagnostic and if worse comes to worse shell be a turned into a little can cause i cant afford anymore work on this car and its not even worth it.

posted by  Rad1

what you were doing is basically a cylinder balance test, either #6 plug is fubar or the cylinder isn't mechanically sound, rings or valves. make sure you didn't mess up the firing order when you did the wires.

posted by  BanffAutoSpa_ap

If the firing order checks out, next you need to check the cylinder itsself, using a pressure tester to determine if the valves are working properly and the rings are sealing as well. If you have noticed increased oil usage or burning you might need to have the engine re-ringed. What kind of motor and junk might help determine some of the problems.

posted by  srober32

i have noticed increased oil usage but that could be cause my block has a crack in it, so i was told by the last owner.

posted by  Rad1

wtf.... cracked block and you still bought it, uh huh, junk the motor get a new one dude

posted by  BanffAutoSpa_ap

didnt buy it, car was given to me,
car started acting up a year ago but still ran and last owner didnt want to wait for it to die so they bought a new car and gave me the shit box to run it into the ground.. i guess its finally dieing...but i was hoping to fix things myself and not spend much money on it to make it last a little while longer.

crack is a very small, i usually add a bit of oil to it every 500 or more km

posted by  Rad1

You performed an "equalisation of cylinder power" test. Sounds like you have a compression problem on number 6. As it's unlikely the rings would wear at a much greater rate than the others I would be doing a compression test as suggested by srober32. You may have a badly seating or burnt valve or maybe this is the cylinder with the crack in it.

posted by  Wally

personally i wouldn't test the engine with this method cars nowadays run from 50,000 to 70,000 volts through those things. did you get shocked at all? if you didn't consider yourself lucky.

posted by  carlos

all it is, is a bad head gasket which in turn is making the compression go down, when you took out the wire and the noise stayed the same, and you just put in new plugs, then the compression is gone. it is not able to bur the gas well and makes your engine stall. either heve the head gasket replaced or adjust your valves

posted by  forster21

Check to make sure the plug is firing. This will rule out something like a bad plug or wire. Get a compression tester and see what's going to with that cylinder. Check for codes - short the two upper right pins on the connector under the dash, turn on the ignition key, and look at the Check Engine light.

For example, if it flashes once, pauses, the two times, that is a Code 12. It will flash each stored code 3 times.

posted by  PeteC

ya gona do some cylinder tests like others have suggested too.
I believe wires and plugs work fine.

Checking trouble codes I would but as far as i know i don't think i have to check that cause my Check Engine light never flashes when driving so as far as the computer knows i have no problems recorded.
I was told that it would only flash if a problem was stored in the computer, can anyone confirm on that...??

Anyways thank you everyone for your help and advice, its most appreciated and i will test things out through out the weeks ahead and let you know what happens for any future references.

but please keep posting if you think of anything else....

:thumbs: :thumbs: :thumbs:

posted by  Rad1

I managed to fix the stalling for now by buying a new IAC valve the other one was pretty dirty and think wasnt goin in and out properly.

The Car very slightly chokes now but not as much as before. The new IAC seems to have made a big difference but i still suspect the 6th piston is screwed and im still gona test it out when i get the time and money too.

What is MFI or SFI...??

posted by  Rad1

Hmmmm I'm thinking, with all that has been said you really have a faulty wire or spark plug on number six. Possibly a dirty plug that cant fire right. You'd be seeing other probs like unusual heating (or overheating), bad milage, and remarkable odors I think if you got any driving out of it at all and it were a valve or piston problem. Not to mention assuredly a backfire or two or REALLY rough engine vibration....especially when starting up or stopping.

Spend the $40 or so for new plugs/wires. Have them gap the plugs at the store for you. I've always found they are better at it than I am. See if that gets any results before you start getting into the block.


PS: After re-looking...I agree with forster21 too. If the simple fix of tuning it up (replacing the plugs n wires) doesnt fix it then dont go deeper into the block. The next logical step is to look at lost compression from a bad head gasket. Good call forster21!

posted by  Blue_Frog

That could be a bit misleading for a newb. You are mixing the physical with the control method.

Most engines are multi point configuration these days, the choice is between batch or sequential operation.

posted by  Wally

True im a newb and a dont fully understand what those mean but I do know on my engine it says F1 Multi-Port 3.1 embossed on the engine block.

So ill do some research and learn a little more about that stuff.

--



And Blue_Frog, ive changed the wires and plugs already, so ya ill be looking into getting the piston pressure tested.
If i can do it myself i just gota get my hands on one of those pressure testers.


Thanks for any info guys.

posted by  Rad1

I'm going out on a limb here, but GM's of those years share a common problem. COIL PACKS. I think u got a blown one. Check to see if any of em aren't bloated of cracked. And they have numbers on em, so u'll know which one it is (6 as u said, curious how u know its #6, anyways).Even if it ain't bloated or cracked, im pretty sure its ur coil. And if uve been driving around like that for awhile, get a compression check cause u may have f**ked up that cylinder seeing it hasn't been firing, uve been having that cylinder flushed with unburned gas. Good luck.

posted by  Carcass

You can put a refundable deposit on most tools (including compression testers) at AutoZone stores. Hell I only have a handful of tools that doesnt amount to much more than a good socket set and screwdrivers. Autozones tool lend thing has saved my azz more than once.

posted by  Blue_Frog

MFI = Multiport Fuel Injection
SFI = Sequential Fuel Injection
TBI = Throttle Body Injection
Three types of fuel injection systems MFI and SFI are similar and TBI looks kind of like a carburator.

posted by  srober32

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