[dghii]

Took a 60 mile ride today to go look at a used golf cart for the kids to drive around the neighborhood. About 10 miles from my destination, the car started to run rough with a very discernible miss. I limped into a small town and pulled into a NAPA store.

As the car ran, I pulled one spark plug wire at a time and discovered that cyl #3 had decided to no longer participate in my trip. I bought a new plug, hoping for the best but of course discovered no change. I had good spark on #3 cylinder
(pulled plug and grounded). The original plug was dry and gray and looked like the others that I pulled for comparison.

For a sanity check, I swapped the #3 and #4 wires but the dead cylinder stayed at #3. I also swapped the the injector wiring between #3 and #4 and still had no combustion on #3.

I made it back home on three cylinders and checked the injector impedances. #3 and #4 both registered 2.9 ohms.

There are no visible leaks etc. This is definitely tied to #3.

I sent my injectors out for cleaning just a few months ago and all my fuel hoses and vacuum hoses are less than 4 years old (fuel rail hoses are new).


Anything else I can do to narrow it down to a bad injector short of pulling it out?

Cars engine has 66K miles and has been in the family since 1986 and has not been apart. I'm hoping I don't have a valve issue but not sure what else to check. There is no smoke or oil usage.

BTW, the golf cart looked like crap.

 

[ghnl]

Make sure there are no vacuum leaks (loose/missing hoses, etc). I've had a disconnected vacuum hose adversely affect one cylinder much more than the others enough that I feared a bad injector, too.

One way you can test the injector in situ is to remove the spark plugs, turn the engine so that the intake valve of the cylinder in question is open (you can peek in via the spark plug hole and see the edge of the intake valve when it is open) then pressurize the fuel rail (switching the key on/off/on/off/on/off should do) and briefly apply 12V + & - to the injector's terminals while watching for the squirt of fuel past the open valve. (polarity does not matter) Please use caution when playing with fuel vapors & sparks.

 

[dghii]

Thanks. I'll try that.

I don't mind pulling the injector, its just that I had the whole intake out back a few months ago to replace the intake runners and rebuild my starter. I took the opportunity to have all the injectors cleaned and new hoses installed between the injectors and the rail. Just hate to have to mess with it again.

 

[pwnage]

Sounds very similar to my problem this spring. Took the car out of storage and it started to run rough. Pulled plug wires off one by one and it was #3 that was skipping. There was spark from the disconnected wire to the head so I convinced myself it was probably an injector issue. I didn't have the clearance to swap injector wires and ended up taking it to a shop that knows cars like this. Turned out that it was electrical. They replaced the rotor, cap, wires, etc. Runs great now, but if I had known, I could have certainly done the work myself and saved a couple hundred bucks!

 

[Slash]

Maybe do a compression check to rule out a burnt valve. I wouldn't expect a valve to burn so badly all at once, but our Bosch-injected engines run leanish and, according to my Alfa Guru, a burned OEM valve is not uncommon even with relatively low mileage.

 

[dghii]

Not the injector.

I have not done a compression test yet as I have to borrow the tester but tonight I managed to pull the #3 injector without disconnecting from the fuel rail. With the coil wire off, I had my wife turn the starter over while I checked for spray.

Unfortunately, the injector sprayed (misted) fuel.

Right now, I assume that the spray is correct as the injectors have recently been cleaned and checked by OK Injectors.

I have spark and like I said earlier, swapping wires made no difference. I pulled my dizzy cap and rotor tonight hoping to find a boatload of carbon or crud under the cap but to no avail.

I put it all back together hoping for magic but again, no joy.

Can I do any other damage driving the car short distances in this condition? Work is 3 miles or so and my other car is at a body shop repairing teenage son damage. I should have the car back soon but may need the Alfa for a day or two.
Keep in mind I've already driven the car about 75 miles in its present condition.

 

[pwnage]

Have you tried swapping the plug?

 

[dghii]

Yes, actually bought 4 new NGK's when I first felt the missing but had no joy. Like I mentioned, I have spark and fuel on all four cylinders but, like a kid, that's not good enough for #3!

 

[jcslocum]

If you have spark and fuel going on at #3 then it must be a mechanical problem. You're going to have to do a compression test.

 

[pwnage]

I checked the receipt again to make sure I didn't miss anything, but after seeing spark, even getting zapped by #3, swapping the plugs, smelling gas on the plug after it was running w/o the wire, etc. I had convinced myself it was not electrical and took it in expecting bad compression or poor injection. The receipt unfortunately doesn't say what they did for the $127.24 DIAG ENGINE SKIP though. It probably was not a hot enough spark to #3. Maybe if your cap/rotor/wires aren't new any more, change them anyway. You can also try and run your engine in pitch darkness to see if there are any spark leaks anywhere along the system. Hopefully your problem was the same as mine.

Cheers

 

[dghii]

Thanks for the encouragement...I hope (wish) my problem ends up being the same as yours! I will do a compression test this weekend.

BTW, Rotor and cap are less than one year old. I pulled them Wednesday night to inspect (looked clean) and hit all contacts with a little sand paper and contact cleaner. I've also swapped wires (#4 and #3) but problem stayed on #3.

 

[ghnl]

Check the intake runner hose for cracks or loose clamps - it's hard to see them because they are under the plenum. All it takes is an air leak and the mixture to that cylinder will incorrect making it appear to be a dead cylinder.

Another thing to try is re-arranging the positions of the spark plug wires. When the wires run parrallel they can induce a 'cross fire' in an adjacent wire.

 

[dghii]

Thanks Eric,
I saw the wire reroute idea and meant to try it.
FWIW, magnacor wires about 2 years old. Intake runners were R&R'd back in April. I will check them though as I let them sit on the shelf for a year or so prior to installation.

Other than a visual check, is there another way to check the runners for leaks? I remember it being kind of fun to get all four lined up and secured at the same time.

Still plan on doing the compression check.

 

[dghii]

Compression test done

I finally got around to doing a compression test this evening. I know, I know, I'm slow...just been too hot and (insert any excuse here) to mess with the car. Anyway, to no surprise, compression is very low in cylinder #3.

Current mileage:68,440 original
Cyl. #1: 175
Cyl, #2: 175
Cyl. #3: 35
Cyl: #4: 165

I have not done a leak down as I'll have to take the car to the Navy base hobby shop to get a compressed air source.

With the plug out, I can see the top of the piston each of the intake and exhaust valves. I don't see anything terrible but of course it is hard to see. I will post pics of the #3 and #4 valves and if anyone see's anything weird, let me know.
Right now I'm leaning toward pulling the head and buying a full up replacement from IAP or Centerline, although part of me would like to keep the original engine together, just don't have any experience with rebuilding a head.

 

[dghii]

A few closeups

Pic #1 is #3 intake, Pic #2 is #3 exhaust and last picture is #4 exhaust for comparison.

 

[ghnl]

Well it sounds like the head needs to come off anyway but a leak down test will help pinpoint the problem. Instead of bringing the car to the shop can you get one of those portable air tanks?

 

[dghii]

Access to the shop is too easy...$5/hour bay (with lift) rental and a double stack of snap on tools (not that I need them all for this job).

Don't know what I was thinking yesterday but I completely forgot to do a 'wet' test. I'll do that this afternoon if the weather permits.

 

[Slash]

Don,

The picture shows a burned valve (at about 30K miles). If you look closely, you will see that the portion of the valve edge that would be visible from the sparkplug hole looks OK.

 

[dghii]

Ron,
Thanks for the pic. Very helpful. I didn't really expect to see much looking down the plug hole but thought it was worth a shot.

 

[Slash]

I agree. Usually, the more info you gather, the easier it is to make decisions on a course of action.