1990 Hyundai Excel - Severe Acceleration Hesitation

[P Plater]

Hi,

I have a 1990 Hyundai Excel 1.5L.

It suffered from severe acceleration hesitation (ie. it bunny hops down the road) in 1st and 2nd gear and especially when cold. When at running temperature, it still does it a tiny bit but no where near as much as when cold. I have replaced spark plugs and checked the ignition timing but it still does it.

If you advance ignition timing more than it is supposed to go, to the point where it pings a bit, the problem goes.

I would like to run a ECU diagnostic but apparently on Hyundai cars, you need a special unit that plugs in which is expensive.

At the moment, I'm thinking that it might be an engine sensor stuffed up sending wrong messages to the ECU but I'm not 100%

Anyone had this problem or got any ideas?

[Reeder113]

Originally Posted by P Plater

Hi,

I have a 1990 Hyundai Excel 1.5L.

It suffered from severe acceleration hesitation (ie. it bunny hops down the road) in 1st and 2nd gear and especially when cold. When at running temperature, it still does it a tiny bit but no where near as much as when cold. I have replaced spark plugs and checked the ignition timing but it still does it.

If you advance ignition timing more than it is supposed to go, to the point where it pings a bit, the problem goes.

I would like to run a ECU diagnostic but apparently on Hyundai cars, you need a special unit that plugs in which is expensive.

At the moment, I'm thinking that it might be an engine sensor stuffed up sending wrong messages to the ECU but I'm not 100%

Anyone had this problem or got any ideas?

Does it idle rough as well? Have you checked the timing belt? How about the O2 sensor? The EGR valve could also be the cause of the hesitation.