Yeah I’ve heard this. What’s a better way to identify which cylinder is misfiring?
You can get a spark tester that goes inline with the plug wire.
You can pull the wire (with the engine off) and connect it to a spare sparkplug (be sure the ground the threaded portion)
The pull the spark plug wire method is usually ok if the ignition system is conventional, points and plugs. With electronic ignition, not advised, the ignition module can easily get zapped.
That cap needs replacing. The black is a combination of carbon and copper oxide, resistive elements. It’ll “drop” voltage as the spike tries to jump the now-larger and resistive-element-coated gap between the rotor and the plug wire connection, leaving less to jump the arc on the sparkplug.
NOTE: you should always change the rotor along with the cap.
Interestingly, carbon is often called a “resistive conductor”. Its resistance drops when it’s compressed. But that’d just trivia, not relevant to your problem.
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Watching for an arc on a spark plug lying on top of the engine is not always indicative of a solid spark on a particular cylinder.
When the spark plug is under pressure in the cylinder it may not fire at all.
An oscilloscope is handy for things like this but is out of the reach of most people. I say spring for a set of new wires.
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I actually have access to both a scope and HV probes. But for the most part, on legacy ignition systems, I bought an inline spark tester for around $10. Works like a charm and takes just seconds to install. I find most issues can be seen with this simple tool. It works on my older cars, outboard motors, motorcycles, ATV etc so it’s paid for itself many times over already.
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I’ve got the car back running on 6 cylinders! Air was leaking past the fuel injectors as the seal was badly placed. I knew this was the issue as i sprayed some starter fluid over the fuel injectors and when sprayed on cylinder 3 fuel injector, the revs shot up. Fixed by taking out all the injectors (attached to rail) and replacing/ cleaning the rubber seals.
My issue now is that since this fix, the car cuts out at idle, as if the idle speed is too slow. It seems to run very well if i give it a tiny bit of gas. Any ideas on fixing this?
When you step on the gas pedal all that does is allow more air into the engine. It may be that the vacuum leaks you had at the fuel injectors were allowing extra air into the engine, and now you’ve fixed those air leaks, the idle rpms is too low b/c there’s less air getting into the engine. So what to do about it? hmmm …
Your car is probably configured nearly the same as my Corolla of similar vintage, electronic ignition, conventional distributor, single coil, electronic pulsed fuel injection, idle air bleed manual set screw, and some type of idle air control gadget right? If so, then the idle rpm may be incorrect. Measure it, and compare to the manufacturer’s spec for warm idle rpm. If it measures low, either the idle air bleed screw isn’t set correctly, or there’s a problem with the idle air control function.
Exactly what is the idle speed? The suggested idle speed should be on the underhood sticker. Too low by even 50 RPM can cause it to idle rough.
The correct idle speed is 900rpm. We adjusted this an managed to get the car running nice.
Another issue. Just taken the car for a drive and it drove really well for the first time. However the car was running rough when we stopped. Left it running for a few minutes. We tried to rev it and the revs wouldn’t climb. So we turned it off. When we came to start it again a few minutes later, it wouldn’t turn. Coolant is leaking out the front of the engine. Any ideas? It seems the engine has seized. I am really hoping it wasn’t overheated. However, the fan was blowing the whole time, there was still coolant left in the reseviour, all the pipes were hot and the oil temp gauge was good. Plenty of oil in there too.
also, I’ve tried pushing the car in gear, and the engine does turn slightly. I’m not sure how much resistance there should be
Try to turn over the engine by hand, using a 1/2" breaker bar and the appropriate sized socket
The radiator fan normally would only blow on long idles, and only rarely when driving about. So it does sound like your Alfa is having some cooling system issues. Overheating could definitely damage & seize the engine, but you need to do a few more tests to decide. Hopefully that’s not the problem. Suggest to start with the one db4690 mentions above.
With the radiator fan running all the time unexplained, best to stop & turn the engine off and figure out what’s causing that to happen before continuing. Did you notice the dash gauges and/or warning lights indicating an overheating problem during your test drive?
George, db4690,
I appreciate the replies. A few days later I’ve managed to turn the engine by hand and, having charged the battery, have now been able to start the car with no issues. What could have happened here? There were no warning signs of that car overheating. The oil temp gauge was at 50/60°C: could this suggest a fault? Seems low. Although as I said, the fan was on all the time. I felt the water pipes and they were too hot to touch.
Please note that when I said the fan was on for the whole time, this is because I’ve hard wired it on (fan switch broken).
Symptoms: Car was running fine but when I stopped driving and left it idling for a few minutes, it was running rough and wouldn’t rev with a fair amount of throttle. I turned the car off for a few minutes and when I came to start it, the engine wouldn’t turn. The lights dimmed and the fan slow down when turning the key, which lead me to believe the starter was engaging.
When running, there was a water leak coming from the thermostat/ fuel pump. Since cooling, this leak is now very rapid even with engine not running.
Any help would be appreciated. Thanks
Happiness is buying an Alfa Romeo, great happiness is selling it.
The obvious thing to me would be to fix the coolant leak. What is the connection between the fuel pump and thermostat?
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If the battery discharges during a short drive there is a charging system problem. The engine won’t run well when the voltage drops below 11 volts and the engine is not going to start until the battery is recharged.
I had this symptom on an old Buick… the timing was set 20 degrees too advanced.
So it was running fine for a while, then it started to idle poorly and wouldn’t rev as fast as it normally did. After turning the engine off, it wouldn’t start the next time. Is that right?
If so, when it didn’t start, what exactly happened when you turned the key to “start”? Did you hear that rrr rrr rrr sound, but it wouldn’t catch and run on its own? Or did it make a click, but no rrr rrr rrr sound. Or did it make no sound at all when you turned the key to “start”? The
If it was either of the last two, which mechanics term a “fails to crank”, that sounds like you have a battery, alternator, or starter motor problem. It may be that running the fan all the time is confusing the charging system. Those radiator fans take a lot of current, and may be stressing the alternator or the battery. Then when it comes time to start the engine, you’ve got a partially discharged battery and it won’t crank.
If I had this problem I 'd do a compression test, and if that was ok I’d fix the fan switch so the fan only came on when it should, and fix the two leaks before proceeding further. Otherwise you’re going to be fighting too many problems at once.
If the oil temp was only getting to 60 deg C, that doesn’t sound like much of an overheating problem. But I suppose it is possible for an engine coolant to overheat but the oil temperature not showing that. Does your Alpha have a coolant temp gauge on the dashboard? Or just an overheating warning light?
As long as the engine didn’t overheat and got damaged, it seems like you aren’t that far away from a daily driver there OP. You want to do the best you can while getting things working to avoid overheating or running low on engine oil, transmission fluid, or coolant. Keep those fluid levels and temperature well monitored until everything is verified to be working correctly.