ok guys my 01 xj was running perfect today and i took it ofroad...nothing extreme just a little bumpy dirt road and some hills.....about 5 minutes after my check enging light comes on.....i get the codes pulled and it says misfire cylinder 1....the symptoms are it runs good for approx 2 seconds then it lulls like lacks power then picks power back up then does it again constantly.....while normal driving....the check engine light is flashing......so i replace the spark plugs....runs good for ten minutes, the idle is in the good range....the compression test was good.....i take it out on the road after changing the plugs....hit a spot in the road where a bridge is a little higher than the road and my check engine light comes back on and it is lulling in power.... so im wondering what this could be....im stumped and am going to replace the coil packs next i reckon...
so anyone else have any good ideas????
thanks
Josh

 

Flashing check engine light means your cat is becoming defective.

 

No a flashing CEL is caused by a catalyst damaging miss fire is occurring. PCM don't turn off injector when a miss occurs.

 

bsmith.....what could it be then? if its not the coil pack or cat converter

 

A flashing check engine light indicates you have a serious misfire, which if ignored, can destroy the catalytic converter.

You've already replaced the plug so you can rule that out. Other suspects include the coil pack, the fuel injector and the internal condition of that cylinder.

Personally, I'd start by swapping the fuel injector with another cylinder to see if the misfire follows. If no joy with that, I'd perform a compression test on all cylinders and see if that cylinder reads lower than the others. I'm not sure how to test the coil pack on the 00-01, if somebody knows how to do that, please chime in.

 

i did the compression test on the cylinders all cylinders were 130 to 150 range.......so the injector is my nxt suspect.....if that doesnt work ill replace the coil packs....since i already bought them but swapping an injector should be easy.....i just dont understand how hittin a small bump in the road is synonymous with the problem..bc as soon as i hit the bump the light came on and the engine started bogging. ...so to swap the injector....should i swap connectors or the actual injector?

 

Actual injector

 

The bump and misfire are probably coincidental = just luck.

The coilpack - The plugs on a DIS fire on every TDC - The firing on the backside - non compression stroke - is called the waste spark.

First LISTEN closely to the coil pack while someone revs it. Often you can hear it shorting inside - replace.

Use an infra-red thermometer - rev it at 2000 for a couple of minutes - go under - measure the exhaust port temps on each cylinder - a cooler one indicates which cylinder is misfiring.
If you have individual pre-cats measure the temps at the inlets.
Typical NORMAL temps are about 350-400 degrees each.
If you have a defective coil rail, one will be more like 300 and the other around 700 degrees. The hot one is on the misfiring bank.

Now that the coil rails have some miles and years on them, they are a common failure.

Be sure to get a real one - lots of cheap Chinese knock-offs around - AutoChina sells them.

Carquest, NAPA, or the dealer (expensive there) have good ones. The difference? 6 months or several years.

 

Good advice rrich....thanks for this information; will tuck it into my 00-01 file!

 

this is good advice thank you and i had read somehwere else online about the waste spark but didnt think/know to test temperatures....will pick up an infared thermometer today.

 

switched #1 injector with #2 injector and put it all together and the damn thing leaks....is it supposed to be hard to push the injectors into the rail. will bad o rings make this difficult?
thanks for all the input, ill keep posting

 

put grease on o ring of injectors so you dont cut an oring... crank sensor could give a misfire code. check wiring to crank sensor. sounds like you got a bad wire somewere.

 

A crank sensor problem wont be isolated to one single cylinder.

 

I agree. I'd concentrate on fuel injector, coil pack, and the internal condition of THAT cylinder.

 

Yep thats where I'd look if it were mine. More towards coil pack actually cause its a "dead" miss not just a little hiccup kinda miss. But ya cant rule out any of the three items that can cause it YET!