98 Excel twincam(Accent there?). After driving for a bit, sometimes a long time, the car will get a bad shock through it like its trying to cut out. Its worse than a single missfire. They get more frequent as you keep driving. Sometimes gets to the point where it stalls. The engine light comes on sometimes when its running bad but goes off and last time we checked didnt leave a trouble code.

What we've already replaced -
Plugs
Leads
Coil pack
MAP sensor
TPS
Crank angle sensor
Cam angle sensor
Fuel filter.

Has anyone had anything like this happen on one of these? I know its an American forumbut i'll give it a shot. This thing is doing my head in.

Only thing left is fuel pump or ECU. These common on excels?[/align]

 

If the check engine light is coming on, then there should be a trouble code. Try checking again.

 

If this were a U.S. car, it would have OBDC-II engine management system with diagnostics that would store an error code. I'm not sure that would necessarily be true for a foreign market Hyundai. Could be a older OBDC-I system or something in between. Regardless, no code is no code and not much can help there.

Question - does the problem manifest itself more quickly or more frequently on a near empty tank of gas compared to when the problem occurs with a full tank?

 

Ok this isnt my car. From what I been told it is worse after filling up the tank sometimes. But this may be purely coincidence.

 

Well, I was hoping it was worse on an empty tank. I have had a couple of cars develop this symptom, but the problem was always worse on a low tank. In both instances, it was a fuel pump going bad that would overheat and eventually trip it's relay. Once the cars cooled off, they would start and run again. It turns out the gasoline not only serves as the fuel for the engine, but is also the coolant for the fuel pumps. With less gasoline in the tank, the pumps would overheat much quicker and take longer to cool off. However what you describe doesn't necessarily preclude the fuel pump from still being the problem.

Until an error code is registered, the owner needs to conduct some further diagnostics when the car has one of it's seizures. I suggest they carry a spare spark plug in the car. When the car dies, this can be plugged into one of the spark plug wire and then crank the engine to see if the ignition is working. If the fuel pump is working, they can either listen for the pump to energize when the key is turned on or determine if the smell of raw gasoline is coming out of the tail pipe after cranking the engine for 20-30 seconds.

 

This problem sounds like what my 94 excel is doing. It pretty much loses all power sporadically. Sometimes, it will come right back, and other times, I have to turn the car off and restart it, and then it's fine for a little while, and it just won't run with less than a 1/4 tank of gas. I was told that it was probably because my fuel pump is weak. I was messing with it today and I tried to listen to my fuel pump run when I turned the key on, and I couldn't hear it. Is it in any way possible that the car will run without the fuel pump working, or could it be so weak that I can't hear it.

 

If the car is fuel injected, it will not run without the fuel pump working pretty much full time to keep the fuel rail pressurized. If the car has a carburetor, then the pump would run more sporadically since it just has to keep the fuel bowl full. I think U.S. cars all had injection, but I know some foreign forum members have discussed carbureted Excels up to the early 90's. If you are checking the pump after trying to start the car or had left the key on, the pump will not activate if the fuel rail is already pressurized. You should hear the pump when you first turn the key after the car has sat for some time, like overnight. The symptoms you describe do sound like a failing pump.

 

I changed the fuel pump on my excel and I still have this issue. It's driving me nuts and causing me to spend more money than what the cars worth. I'm beginning to think it may be a problem in the electrical system, and I dread that. Any help would be greatly appreciated.

 

Did you look inside the fuel tank? A lot of times in older cars gunk forms on the walls, and swills around the bottom of the fuel tank. It can clog the filter screen before the pump inside the tank. Used to happen a lot in Chrysler products, and my old Mitsubishi Galant had it real bad. The solution is to pull out the pump (if it's inside the tank) and look at the condition in the tank, or if the fuel pump is outside the tank, pull out the fuel gauge sender and look in the tank.