No power in low to mid RPM under load

[Shaun_E]

I am struggling to diagnose this one. The car idles OK although it occasionally stalls. With car out of gear, when the throttle is moved slowly the revs increase as expected but a fast movement of the throttle causes the engine to bog down or even stall. On the road there is very little power until revs reach 5k+ when power returns and car launches down the road as expected. Changing gear, revs drop and the power is gone again. It's hard to describe ☹️

Initially I thought it was a misfire but it's much worse than that - it's as if the map is all wrong.

So far I have replaced TPS, coil, ignition leads. I have had the laptop hooked up to the ECU and all readings appear normal (throttle position, air temp, coolant temp) and the map is not corrupt.

Suggestions as to what to do next gratefully received.

It's a Duratec with Emerald ECU but I don't think the engine type is relevant to the problem.

[Guest]

Air leak (induction side)?

[oilyhands]

Shaun,

 

Load the Emerald software and upload the map from the ECU, the. Select the injection map tab and try revving the engine to track where the ECU thinks it is! it may be the TPS needs aligning or the ECU is getting confused inputs from somewhere.

 

Oily

 

 

[Shaun_E]

I'll check for air leaks but pretty sure it's OK.

Thanks for the suggestion Dave - I'll give it a go. It certainly seems like the ECU isn't finding the right bit of the map. I'm only just getting to grips with the Emerald software so it's pointers like that which help.

[simonpa]

I'm in Fleet, Hants - if you are anywhere near, I have laptop and cable..

 

Cheers - Simon

 

[Shaun_E]

Thanks for the offer Simon - I have laptop and cable. If I can't find a solution though I might be looking for an ECU to borrow just to eliminate that from the equation. Is your's a K3?

I'm near Tadley so not too far.

[simonpa]

No car or ECU, sorry.

 

Seen a couple of cars with running issues. Never been a K3 issue though.

After TPS, I'd check the TPS plug (had this giving problems when warm), air leak (had this) and cam belt.

 

Are you running throttle bodies? normally easy to check if they are out of balance.

They can give similar symptoms to yours.

[weeman]

Popped into Tom's today Shaun and I see your car is in good hands

It'll be interesting to see what he discovers.

 

 

[Shaun_E]

I gave up in the end and took it to an expert

I swapped out the ECU (thanks to Tony Whitley), I've logged all the ECU parameters and nothing seems out of place. The map looks OK (on the graph) and the ECU goes to expected map points when the throttle is pressed. I've replaced coil, plug leads, plugs, TPS and even the alternator! I have good fuel pressure (steady at just over 3 bar). Only the CPS left to replace but the car would be unlikely to start if that was the problem.

Of course when I drove it into Tom's workshop it behaved perfectly

Hopefully Tom can quickly find the problem.

[Birkin S3 ZA.]

Did you check the crank position sensor gap? I know its a fixed position but after fitting a under drive pulley I had to elongate the holes to adjust it.

 

It would start and idle ok but gave a few problems when trying to rev it, it did show on the Omex start up map as tooth time going on then off again.

Chris.

[Mr Locust]

Does the fault correspond with parts of the map configured to run closed loop on the lambda sensor?

 

What is the live lambda reading on the screen when it misbehaves?

[elie boone]

If it has a MAP sensor this could be faulty

[Shaun_E]

No Lambda and no MAP sensor fitted.

It could be the CPS but not sure how to check it as the Emerald software doesn't show a parameter for it that I can see (other than RPM) - I'm sure Tom will check it out.

Occasionally it just cuts out when idling and that happened once the car was in the workshop.