Firing on only 3 cylinders

[Kitty]

Okay, so Marvin is home. (Hooray!)

I still have to replace the driver side control arm. We were only able to get the passenger side one off the Organ Donor car. The driver side was bad.

However we discovered after everything was put back together and he was sitting there idling waiting for me to take him home that he is only firing on 3 cylinders. And who knows how long this has been going on. The faint "plut plut" noise that occasionally comes out of his tail pipe has been there since I bought the car so I never thought anything of it. And when you listen under the hood he sounds perfectly normal.

So here's the question. Is this something I have to worry about RIGHT NOW? If we had realized this when we had everything out already we would have just dropped in the back up engine and gone from there. He runs about the same as he always has. Well, a little better actually. Power doesn't seem to be affected, gas mileage. He's just running on 3 instead of 4.

The mechanic didn't think it would be too much of an issue to run him like this for a while longer (since we don't know for sure how long he's been running like this anyway) but I wanted to get expert opinions here.

[FestYboy]

Hello Kitty!!! (sry couldn't resist)

anyway, find yourself a LONG screwdriver or something that resembles one. place the tip on an injector housing and the butt end at the top of your jaw just outside your ear. do this while Marvin is running. take note of the sound you hear, and move to the next injector. repeat till you've listened to all 4 injectors, if one sounds different than the rest, that's your culprit. take the screwdriver, flip it around and firmly smack that injector with the butt end (handle). if the engine emediatly changes tone, you've fixed the problem. then run a strong concentrate of seafoam and marvel mystery oil in your gas tank.

if all the injectors sound the same, pull the spark plugs and inspect them. they may be fowled.

[jglutz]

Running on 3 of 4....has to be proven....the reason I say such....if it was...the power would not be the same....it should be considerably different/insufficient.

Best way to prove such is whilr the car is at idle....pull the ignition wire to one cylinder at a time. When a good cylinder is disconnected, the idle should drop considerably. If the idle does not drop, you have located the bad cylinder.

If the idle reacts the same for any of the cylinders disconnected; I would check the timming, fuel pressure and inlet air flow.

If one cylinder seems to be the problem, try swaping an ignition wire and spark plug to see if the problem follows such.

No car...especially on you're not sure of the history....would be hurt by having the ignition (rotor-cap-wires-plugs) from being changed.

It could be a fuel injector but i would suspect that last.

Driving the car durring the interum could be harmful! A lean (not running cylinder) could run extremely hot and cause unwanted damage.

[Kitty]

Okay, I guess I should have added this information.

While Marvin was in the shop he got:

Transmission (from the Organ donor)
New clutch
New water pump
Replacement seals on the engine (and valve cover gasket)
New timing belt
New plugs, wires, cap and rotor
One control arm replacement
Replacement gear shift and all the little do-dads it is hooked to to keep it from flopping around
And a partridge in a pear tree.

We've already done the wire pulling test. We know which cylinder it is that is not firing. I'll try to do the injector test thing tonight if I get off from the second job early enough.

[jr.fester]

dang it I didn't read before posting. guess my idea's were covered already.

[edudu77]

I'm with jglutz, you should not drive the car. Aside from the cylinder getting hot, the fuel can wash down the cylinder. All that gas goes somewhere..in this case, straight into your oil. The oil thins, and if run like this long enough you could ruin a bearing. Good luck finding the culpret, hopefully it's just a simple fix.

Donovan

[Kitty]

I've been chatting with a friend in Gtalk today too. He's been giving me some troubleshooting tips as well. I'll be digging out the toolbox tonight!

[WmWatt]

Um, if you pulled the wire from the bad cylinder then you tested and know if it has spark?

[mechanicaldj]

do not ever think:

because it is new, it cannot be bad

factory defects are all the rage these days

[FestYboy]

if an injector isn't firing, it can't wash down the cyl.

[FB71]

^^^ agreed. And either an injector or spark related misfire will NOT cause the cylinder to overheat. In fact, it will cool it down.

[Kitty]

I wasn't able to get under the hood last night (it was raining and I don't have an umbrella big enough for both of us) but I did get a can of Seafoam to put in the tank. I'm going to take him down to the in-law's tonight so I can get in under their carport to work on him. If whacking on the fuel injector doesn't do any good I'm going to pull the plug and check it out. See if it's wet or dry and check the gap on it. I'll probably swap it around with another that is confirmed working just to be sure.

[FestYboy]

you should listen to them as well (the injectors)

[Kitty]

About all I managed last night was confirming it wasn't the plug wire (it kinda stings when those things zap you). I put the Seafoam in. Don't have a screwdriver long enough to listen to the injectors but this weekend I should be able to catch the in-laws at home to borrow tools from Pop to do that and to pull the plug to check on it. From there I'll check out the wires to the injector and make sure it isn't something silly like one of them broken or something.

[geezerstiva]

if it still has normal power and everything, then it may only be missing at idle. my current car does this. i have absolutely no idea why, but i still drive it. its plenty peppy once you get it revved up a little, it just idles on a miss. i'm beginning to think the reason is just piston rings wearing out. just a suggestion after all your electrical is ruled out.