I have now changed the distributor cap rotor arm plug leads front and rear timing sensors. the car starts and runs then cuts out. lots of smoke as well. today I changed the water temp sensor and things changed slightly. the car fired up and still ran with lots of smoke but after about 30 seconds the engine changed note and began reving erraticly dropping to 800rpm then back to 1100 rpm in quick and continual succession. due to a bad oil leak I haven't yet traced I turned the car off. she ran for approximately the same length of time as before but without cutting out, I turned her off which to me was progress. I have ordered an air temp sensor for the air box but wondered if there was any other suggestions? if you need any more info I will try to explain it more. bit concerened by all the smoke though the engine sounds good. all help much appreciated, thanks to gene for the great advice so far

 

Brinny, your profile says you have a 3.6, 4.0 and 5.3. It'd be helpful in helping you to know which one you're working on.

 

Sorry it's the 5.3. Thanks for pointing that out

 

from my experience "hunting" is usually a vacuum leak or port unplugged, with mine it was leaky cross over pipe connections. Make sure your CTS and ATS are not using each other's plugs and check that the AAV pipe is pulling air and also not "cycling" or stuck. Do you have the one wire or three wire O2 sensors? Bad sensors could switch the ECU from closed to open loop and back again. Also are you running Lucas or merilli ignition? Make sure the vacuum pipe on the back of the cross over is connected and pulling a vacuum all the back to the ECU in the boot.

 

thanks for the help.i don't know what you mean by cts and ats ? it is marelli, once again thanks

 

ATS = air temp sensor
CTS = coolant temp sensor

Their plugs are marked on the factory harness but can get switched due to there proximity to each other.