I am experiencing severe misfiring after journeys of about 1 hour. The problem gradually gets worse and worse until I am forced to pull over and turn off the engine. If I wait for a minute and re-start it's ok for about 15 minutes and then starts to misfire again. The garage have looked at it 3 times but have not been able to fix it. Has anyone come across this and if so what did they do to fix it?

Since the overseas folks were able to get several different engines, a year of your Jackaroo and what engine you have would go a looooong way in helping you figure out your problem.

Michael

1999 3.5 V6 Auto

I'd check the plugs and possibly replace them. And IIRC, it's coil on plug so possibly do a resistance check on the coils themselves. And if you can, get the coils nice and "warmed" up when checking the resistance too. Sounds like they might be going too high in resistance was they become heated up due to the engine heat, etc. Just some suggestions ...

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />

Good first start!

These engines are VERY picky about which plugs they use.
If the engine came with NGK's, put NGK's back in it.
A lot of these engines came with Champion plugs, and
work best with Champion plugs.
The ion sensing knock control spark system is very finicky
about plugs.

Did they use ion sensing in 99? I didn't think so...I used several different brands of plugs in my old 99 Trooper without any problems.

I had the same problem with my 89 amigo. It turned out to be the fuel filter. I had recently replaced the pump in the tank and apparently broke some rust loose. I had cleaned the tank screen and replaced the external filter when I replaced the pump.

After driving for a while (20-40 minutes) the rust would build up against the inside screen of the filter and block flow. When I turned off the key and restart the particles would drop to the bottom of the filter and I would be good for 10-20 minutes.

When I pulled the filter and tapped the inlet on the ground large pieces of rust came out. Later I had to clean the screen in the tank. The screen looked like it was plugged with dirt so I suspect bad gas.

I replaced plugs and wires and ran basic checks on the coil during t-shooting but it didn't make any difference.

Bill
89 4X4 Amigo