Looking for some insight on a problem I’m chasing with my 2003 Disco. I have this terrible shudder and hesitant acceleration from 1500-2000 RPM. It’s been starting rough and misfiring when in idle (park and drive). I’ve replaced plugs, wires, coils, use only 93 grade octane, injector cleaner, replaced the driveshaft, replaced the SAI solenoid valve and pump, and still nothing. Every part I use is Bosch OEM or from Atlantic British/Rovers North. I have zero codes except P1590 for the 3 Amigos. The truck has 142,000 miles.

I’m at a loss and am unsure what to do. Any help is appreciated! Thank you!

 

Applying some logic tells me if no mis-fire codes, then it is not misfiring. So, what else could make the engine run rough?

Check cylinder compression. Check for exhaust gasses in the engine coolant to rule out head gasket failure.

Read live data scans. Check fuel trims and O2 sensors data.