Hello.

Hello.
I have a 96 f150 4x4 with 4.9 boltaction and 4wd.
It has an issue with timing/misfire. It starts fine and for 30/45 seconds it runs fine, then it starts to miss intermittently.
With my scan tool I can see the timing jump, momentarily to 15 to 25 degrees or so. Randomly with no apparent cause.
This happens at idle, parked or moving and at all rpm and load.
It seems to get worse maybe after driving a while.

I have changed pretty much everything in the ignition system.

This has kicked my *** and I’m in need of help.

 

I believe a misfire is the cause for your timing issue. I would check fuel delivery (pressure) , ignition and check compression. I would make sure the basics are in working order before digging in any deeper such as processor functions.

You could try disconnecting the spout connector and see how the engine behaves.

 

Done all of that, to no result.
have tired another ecu also

there is a misfire sometimes. #6 seems to be culprit. I’m not sure why.

 

Why does it not happen for first 30 seconds or so after start up? A misfire would/should happen right away?

 

What does the plugs look like? I have had both of these happen before. A small amount of oil can work its way past a worn valve seal during shutdown, finding its way onto the plug causing a misfire. After the engine has started, the oil burns off and the plug fires correctly. I have also had the same condition happen with a head gasket begining to fail allowing a small amount of coolant onto the plug causing a brief misfire for the first 30-60 seconds after start up..Something to look into...

 

Plugs are new. I haven’t seen any fouling. I don’t suspect head gasket, I can check again. I did I comp test recently, all were within a reasonable amount of each other.

 

It misfires after it’s been running a while, 30 to 45 seconds after starting.

 

It misses/timing jumps 30/45 seconds after startup

 

This might be irrelevant, but make sure your MAF sensor is clean along with the EGR or any other sensor in the path to ignition. It seems to me that if the misfire does not start right away, that the PCM is getting some information from a sensor and adjusting, causing a misfire. Make sure you use proper cleaners for these sensors. In my personal experience, I have cleaned or replace some of these sensors and that smoothed out my engine.

 

good idea. I agree that it’s getting some bad signal after start up.
i have cleaned it, with the correct cleaner spray. Maybe I will replace it.