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Seat Ibiza ('94) starts o.k. but runs rough after 5 min

Hi everyone, I hope for help from anyone familiar with this problem and you have my great appreciation in advance for giving advice: My girlfriend’s '94 Seat Ibiza (similar to Volkswagen) starts o.k. and runs well for some minutes; then it feels like either it is not running on all cylinders or is about to shut off because of insufficient fuel supply. Five more minutes, and it runs smooth and fine again.

We had similar problems last winter, but then, it didn’t start at first and the reason were bad contacts of the wires to the spark plugs at the right side of the engine. Cleaning out any moisture and some contact spray did the trick back then.

What’s different this time is that it starts well and won’t do anything strange until having been driven for some minutes. Is it possible that ice accumulates somewhere, melts when the engine gets warm with moisture now causing trouble, and once the engine gets really warm, the moisture vaporizes and goes away so everything is fine again? Or is it the fuel pump or something completely different?

We have freezing temperatures here in Munich, GER, right now, just around the freezing point during the day and cold at night.

Any help is greatly appreciated!

Guys, I looked this one up and it appears to be a VW Golf/Rabbit family variant (built by VW) available in a variety of gas and diesel engines. The reference to spark plugs and spark plug wires “tags” it as a gas engine.

If cleaning the wires and using contact spray cleared the problem a year ago, it may be time to simply replace them. Along with the other normal wear ignition components like the distributor cap and rotor.

Thanks, the_same_mountainbike. Yes, it’s somewhat similar to a Golf or Polo, and indeed built by VW (with many VW parts inside). And it’s a gas engine. (90000 miles)

I also think it might be time to replace the distributor or maybe the spark plugs or their wires, I just think that the strange behavior of the car starting fine (usually the bigger problem on cold days?), then running rough after some minutes, and then running smooth again might give a certain hint towards the particular problem?

The gas pump should not be the issue, then?

Fuel pressure can be readily tested, but plug wires and worn out ignition components can easily cause intermittant operation, and since your actions last year were a temporary “fix” they’re clearly well overdue replacement and would be my first suspects.

I’ll even bet that if you run it at night you’ll see arcing through the wire insulation from the wires to ground.

Can you get a comsumer oriented repair manual over there?

Well, it’s certainly not the catalytic converter, since it doesn’t have one, and we cannot ask about the check engine light since it doesn’t have one of those, either…

Since your problem seems to be temporarily cured by improving the conductance of ignition wires, it is possible that moisture is a contributor. After 15 years, you may need to check a few sources of electrical problems. Here is a short list (typical wiring order).

If you see the color green on wires where they attach to connectors, assume the wire is corroded for much of its length. Corrosion causes resistance. In that case, moisture along the circuit would provide a nearer and better-conducting pathway to ground until the moisture dried up.

Replace wires with corroded connectors.

If you see missing and cracked insulation, replace those wires.

Sometimes a positive wire will be hot to the touch. First, be careful. Second, suspect a hot wire of corrosion. High resistance is translated into heat.

Battery minus terminal to ground at the battery and the body.
Battery positive termininal to starter at battery and starter.
Starter to generator
Generator to distributor
distributor to ignition coil
Coil to plugs
Engine to ground

Thanks again. Considering it’s maybe not a ‘no contact’ problem, but an ‘undesired contact to ground’ problem somewhere, this would be a good explanation if thrown together with my guessing towards the problem happening while the engine is just somewhat warm:

While cold, the undesired short circuit won’t develop as easily, because ice isn’t as good a conductor as moisture is. When the engine is just a little warm, the ice will have turned into moisture, providing a path for the current that should run through the spark plugs but doesn’t. On the hot engine, the moisture will be gone and all the isolating surfaces will work well again.

I’ll check if I see any arcing and I’m sure I’ll find some repair info (doesn’t have to be English, my first language is German, I just chimed in on this forum because I like Car Talk a lot and figured this might be one of the best places to ask a question about a car problem…)

Thanks for the tips. I have experience with electronics (and high voltages), so I won’t do anything stupid. I just don’t have that much experience with cars.

The car actually does have a catalytic converter. It’s old, but not ancient :wink:

I’ll go through your checks. I’ll definitely notice corroded contacts and take care not to get in the way of the sprak plugs’ voltages.

After considering all the advice given here, I will take care not to overlook damaged insulation. Seems to be the first reasonable thing to look at.

Well, thanks for your advice so far. We checked today, and cleaned all the contacts of the ignition wires. I think we can rule out the ignition as a cause of the problem because everything in there is pretty new and the car really starts like a beauty when the key is turned.

I found this thread in the forum
and what is said there really sounds a lot like our problem. It seems that we might want to replace the fuel filter. Except that giving it more gas really is a good cure for the problem in our case. It also accelerates very well when you step hard on the gas, which leads me to believe we don’t have trouble with the fuel pump (and maybe filter?). When you roll towards red lights and don’t give it any gas, that’s when the engine runs rough and is about to die. Once you floor the pedal, it’s good again.

Another question: What would an old air filter do? What would happen when there’s a leak somewhere between the air filter and the motor itself?