here is my lastest problem

[ralasa41]

Hi all Pete from OZ here , need some input for this , 1997 SOHC V6. about a couple months back replaced all the timing chains all went well, motor ran great , just recently noticed no water in the radiator its all in the engine, took 4 heads in and found cracks in 2 off them and 2 OK had them recond, ( I have 2 complete explorers), rebuilt it all all new bolts and gaskets , now for the problem,
motor starts great , runs perfect, very reponsive for about one minute, then starts to run rough, no power untill you flog it, I have checked for vacuum leaks, replaced all the vacuum lines, replaced coil pack, spark plugs and leads, maf sensor, just about everything on top of the motor, not sure why it runs so good first up , anyway any suggestions, cheers Pete

 

[5.0L V8]

Go get the timing checked again. Maybe it jumped timing after the head re-install?

 

[ralasa41]

Thx for reply, I thought about that, but it does run perfect for a while.

 

[2000StreetRod]

ECT sensor?

Do you have any diagnostic trouble codes (DTC)?

I suggest testing the engine coolant temperature (ECT) sensor. It has a significant impact on the Air/Fuel ratio. BrooklynBay has a table of resistance vs temperature in one of his helpful threads.

It takes about a minute for the O2 sensor heaters to warm up the sensors and for the PCM to transition from open to closed loop. A DTC should be present if you have a bad O2 sensor heater.

 

[ralasa41]

Thx for that, good point about the ox sensor , it does have new ones in but I will check them out

 

[delexploder]

Also if that coolant made it into your cats it could cause issues with o2 sensors not to mention the cats themselves

 

[budwich]

as indicated, likely issue with cats "contamination". Get some live data monitoring going to look at what is happening from the "running good" to "running bad"... they will likely give you hints as to where to look for a solution.

 

[ralasa41]

update

This problem is now fixed, motor runs good, now this seems strange to me but I noticed I had the oxygen sensors on the wrong sides, on the wiring loom it says left and right side, I had them around the wrong way, now I cant see what difference that makes, so I swapped them back to the wrong side again just to check and motor ran rough, seems strange to me, anyway all good thx to those with suggestions , Pete

 

[2000StreetRod]

left & right fuel trims

The PCM adjusts the left and right short and long term fuel trims based on the readings from the O2 sensors. When the O2 sensors are cross connected the PCM can't correlate an air/fuel ratio adjustment with the O2 sensor results. Your engine ran good for the short time in open loop after start up.

 

[ralasa41]

thx for that streetrod makes sense now