V8 EFI running badly any ideas welcome

[Chubster]

Any thoughts on this welcome as I have run out of ideas now Rover V8 EFI, running standard everything and a 35-DLM8 dizzy which is known good, coil also good. Timing confirmed OK static and dynamic, good fuel pressure with no drop off at higher rpm, engine starts first time, every time and idles no problem. Emissions checked and a little high but boarder line MOT pass/ fail, so not massively over. However when running on the road as the revs go above 2500 a hesitancy occurs that becomes restrictive but the engine still revs (roughly), it is audible as well as physical, sounds as though the air control unit flapper door is coughing/ feels like a miss fire. The hesitancy is similar to running with a choke out or when you run a normal coil on a car that requires an electronic one? I have checked through the components with a multi meter and all OK, I also have swapped all the major items as I have 3 complete systems and the same fault with each...Sounds like ignition somewhere but at a loss now?

[Cobber]

Are you getting a good current supply to the ignition system?

[Chubster]

12.35 volts at the coil with ignition at position 2, good voltage also at the battery with the car idling.Spark on idle is also good, using new standard spark plug leads.

[Cobber]

Don't s'pose you can check it on an oscilloscope?

[FI Spyder]

My car wouldn't run above 2500 rpm and bog done when the coarse fuel filter mesh in the fuel pump was partially blocked with flaking from failed sealer in tank. Would run fine all day if I kept it under. Now it is a 4 cylinder FI but same should apply. I would check the fuel filter and the screen on the input on the pump for blockage by water/rust/ant other foreign stuff. Only way to check the filter is to put a new one on as they are metal.

My stock Bosch would overheat trying to keep up the flow at higher rpm and needed to cool down 10 minutes before working properly again if I put it in the red zone. Don't know if that would apply to your installation.

[Chubster]

Tried this but to be safe have fitted a new item and the fuel pressure gauge is fitted post the filter so is showing pressure at the rail, reads 36-40psi even at higher rpms. Tank was replaced a couple of years ago so not original item so should be Ok ish.

[Chubster]

Haven't tried it on a oscilloscope.

[Hasbeen]

I had a very slight hesitancy in the 7 for a number of years. I thought I'd cured it a number of times, but it always returned. It would always disappear after 10 or 15 kilometres or so. By the time I got to town to the auto electrical people, there was never anything to check.

Finally it cut dead, & we found the module in the Lumenition was the problem.

Apart from that, I have had problems with dirty injectors either not passing enough fuel, dribbling, or giving a solid jet, rather than a spray, at higher openings.

Hasbeen

[Chubster]

All the injectors were replaced from a car that was running well before removal, since that each injector has been swapped individually engine ran and each gave the same condition. Given the number of times each of the components have been swapped out and each time the same condition remains.Each component has been checked, swapped out, measured electronically and all in their own right are OK......I think it something very basic that I have missed or not done on the wiring or ignition side.

[sonscar]

Do you have the cold start injector?This may be faulty of thethermoswitch is faulty.Is the air valve at the rear of the plenum working correctly?.The fuel could have water in it.Check everywhere for airleaks.Non of this may be helpful but they re things I have experienced with my non TRV8. Steve..

[FI Spyder]

There were some bad rotors out there a few years back. It was brought to our club's attention by a Jag mechanic and he brought a new good one and a new bad one to show the difference the way they were made (it was a design defect not a bad batch with a manufacturing defect). Can't remember how to visually tell them apart now but what was happening was after as few as 50 miles of use the spark would travel to ground through the rotor. I can't recall if it happened first at higher rpm but I suspect it would. Bad rotors have since turned up on this forum so I don't know if they've been worked through or if they are still sitting on parts selves waiting to catch people out. Maybe something to do a Google search on to investigate.

[TR Tony]

This is the Lucas "Flapper" system? You seem to have checked everything very thoroughly. Is the mechanical/vacuum advance working correctly? The EFI cars had a more aggressive advance curve than the carb cars (although the overall advance is the same) so is it the correct distributor?

If you are sure it is not ignition have you changed the coolant temperature sensor (not the one for the gauge, the one for the ECU?) Also have you checked the setting of the throttle potentiometer - these can wear out but I have heard that you can run with it disconnected to see if it makes any difference.

[Chubster]

Thank you, will check and advise.