engine running rough through out the rpm range???

[slideways]

Hi all
I did post the question a couple of weeks ago but no replies,so i thought i,d try again..

The car ( a 4.0l serp engine)was running fine the after leaving it for about 3 hours i started it up and it stalled,
this happens now and again so wasnt that worried, started again and had to keep bliping the trottle to keep the thing alive, anyway drove it home from work about 150 miles there was a distinct lack of power throughout the rev range and the exhaust sounded louder and deeper.
i've only just service it so its had new plugs cleaned the stepper motor, new air / oil filter,
it has magnicors on it that are 3 years old,
i reset the ecu which made no difference either cold or hot.
so before i spend a lot of time and money trying to find whats causing it can anyone point me in the right direction of what to look at first then in what order to check things and how.

and finally i was thinking of removing the precats do i need to change the tune resistor or is that just for a complete decat??
Thanks
Rich

[GreenV8S]

Loss of power + louder + deeper sounds like either one (or more) cylinder down on power, or perhaps a misfire. The most likely cause is an ignition fault. Suggest you check the exhaust header temperatures to see whether one is obviously cooler than the others (that might point out a totally dead cylinder but may not be conclusive if it's just a poorly one) and also see what the plugs look like.

[slideways]

if that is the case what should i expect for a rebuild??
Rich

[GreenV8S]

slideways said:

if that is the case what should i expect for a rebuild??
Rich

To fix an ignition problem? Nothing frightening.

[slideways]

sorry i ment an engine over haul.

Rich

[GreenV8S]

slideways said:

sorry i ment an engine over haul.

If you mean to fix this problem, I would guess a couple of hour labour plus whatever parts are needed (nothing very expensive). If you mean completely rebuilding the engine that's far more expensive, potentially thousands of quid, but none of the symptoms you've described suggest a need to do anything like that.

[paulathome]

Rich,
I had a similar fault to yours not to long ago. It would be running fine and then start to require a touch of throttle to keep it from stalling. After many hours of faffing about and looking at lambda sensor outputs and fuel injection faults I found that the wires to the coil were loose.
Tightened them up and the fault cleared. Then it happened again a week or so later, this time I found that the mini timer type connector on the ignition amp had been fitted wrongly. Instead of the pins on the amp going between the the 2 spades in the socket they were going down the side of one of the socket pins and causing a poor connection to the coil.
Bear in mind that the coil takes quite a lot of current so any poor connections on the LT side could cause grief. Give all the grotty wires in and around the coil area a good coat of looking at.
Hope you sort it. Let us know how you get on.
Cheers.
Paul

[Barkychoc]

If you've just had it serviced I would suggest you go back there as your first port of call.

[slideways]

Thanks for all the replies
first of all i sevice it my self and its been fine for about a month,i havn't looked at the coil connections yet so i will, the fault happened after turning it off for a few hours and has been there since
Rich

Edited by slideways on Saturday 26th July 04:48

[slideways]

I Think i found the problem.
after doing a night shift travelling home in the morning to see my daughter then driveing back to work for another night shift round trip about 300 miles the car died on the M4 fuel pumps buggered got the AA to recover me to my place of work and in the morning they are comming out to fix the car i hope(touching a large piece of wood). if not they said they would recover me home 150 miles.
all in all a busy day. well 48hrs