99 XJ surging at idle and acceleration

[Leighbus]

it started off a few weeks ago with an intermittent cranking but not starting problem so i replaced the crank angle sensor, when that didnt fix it i replaced the plugs, leads, dizzy cap, rotor and coil, by this time the symptoms had changed to starting fine but then once warmed up would start to surge/missfire then eventually be running so badly that it would stall, once the engine stopped at this point it wouldnt start again untill the next day however some days it wouldnt start at all.

So i took it to the auto electrician where after having it for four days they eventually diagnosed and replaced a faulty camshaft position sensor. unfortunately this didnt fix the problem completely, instead now it starts fine everytime but starts surging straight away at idle and under acceleration, also if i take it for a drive up the street i can hear the engine pinging when accelerating.

Here is a video:

You Tube

since then i have checked grounds, dizzy and tried swapping TPS and MAP sensors off a mates working XJ and still no change. Also worth noting i checked spark with a spark tester and everytime it stumbles the spark disappears so it has me convinced it is an electrical problem and not fuel.

[mtd]

Originally Posted by Leighbus

it started off a few weeks ago with a intermittent cranking but not starting problem so i replaced the crank angle sensor, when that didnt fix it i replaced the plugs, leads, dizzy cap, rotor and coil, by this time the symptoms had changed to starting fine but then once warmed up would start to surge/missfire then eventually be running so badly that it would stall, once the engine stoped at this point it wouldnt start again untill the next day however some days it wouldnt start at all.

So i took it to the auto electrician where after having it for four days they eventually diagnosed and replaced a faulty camshaft position sensor. unfortunately this didnt fix the problem completely, instead now it starts fine everytime but starts surging straight away at idle and under acceleration, also if i take it for a drive up the street i can hear the engine pinging when accelerating.

Here is a link to a video: http://www.youtube.com/watch?v=LInZZGfAsas&sns=em

since then i have checked grounds, dizzy and tried swapping TPS and MAP sensors off a mates working XJ and still no change. Also worth noting i checked spark with a spark tester and everytime it stumbles the spark disappears so it has me convinced it is an electrical problem and not fuel.

unplug o2 sensors and go for a drive. if it drives ok change o2 sensors.

[Leighbus]

I have tried unplugging front o2 sensor only and it made no difference but I might give both a try

[darksidecustoms]

You might also have a vacuum leak somewhere.

[Leighbus]

Tried with both o2 sensors unplugged still no difference. Also this time I run it for a while and let it get really warm (above normal temp) and noticed it was much worse when really hot to the point that if I revved it to 1200rpm then took my foot off the accelerator the rpm would stay there for about 10sec then it would return to normal idle, sometimes it would even go up by itself like it had a mind of its own. However while doing this I was watching the sensor output data on my OBDII scantool and all sensors including TPS seemed fine.

[rob-rock]

my jeep did a similar rough/high idle turned out that a misfire out the intake, blow the brake vac line off the intake.maybe your brake vac line is leaking
or a cracked intake, mine where cracked 2-4 on the under side ='(
you can view them from looking up along the exhaust to the intake

[DarrenR]

The cranking but no start does point to the crank angle sensor but part of that circuit (the ASD circuit) is the ASD relay and fuse, its a common fault that the relay dies or chatters, swap it for the horn relay. XJ2 the relay is rectangular, early XJ its a standard square one, both common.

Also keep in mind a faulty crank angle sensor wont always throw a code, actually more often than not they dont.

The running but eventually dying, have a look at the wear on the dissy shaft (sideways movement), high mileage its common for it to be worn.

Regards
Daz