Forum » General Tuning Discussion » Engine starts and idles but will not rev

Engine starts and idles but will not rev

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
1130 Views

I am hoping someone can help with this as I am running out of ideas.

I have just reassembled an EJ257 that has been running in the past with the only difference in setup is that I have had 1mm oversize valves installed.

The car is running a Haltech PS1000 with wideband controller .

The fault is that the car starts and idles quite well but will not rev past about 2500. As I open the throttle the indicator on the map just travels across towards atmospheric pressure but not upwards in RPM.

When I inspect the plugs they are fouled and number 4 is often washing.

With that in mind I,

Compression tested the engine, 160psi all around

Changed out spark plugs, multiple sets

Tested coils, I am getting a 3cm spark from each

Changed out number 4 injector as I thought it may not have been closing, washing, reading lean and then I would be lifting fuel in the other 3 to get lambda at the sensor.

I have listened to all 4 injectors wit a stethoscope and they are all switching.

I have disabled rev limiter and engine protection

The reference triggers are rock solid

I have watched the ignition timing numbers which appear correct

TPS is set correctly and all other inputs appear to be linear in behaviour

The 02 sensor is a brand new LSU 4.9

I have raised and lowered the transient throttle enrichment settings

Sometimes when I feather the throttle I can get it to rev but it is rare. At one stage if I feathered it to about 3500 it would take of and rev normal if I kept it above that rpm. The fault resumes after returning to idle.

The VE numbers are a lot lower than I am used to seeing on this engine. I normally see around 60 at idle but currently to achieve lambda it is closer to 30.

I am seeing about 2ms at idle with ID1000s.

This car has run with all of the same components before barring the valves and it has me kind of perplexed. Any help would be greatly appreciated.

Also, just to eliminate a settings issue I reloaded maps from 2 years ago. No Change.

I also removed and inspected the Catalytic convertor for blockage.

How sure are you that the CAM is timed correctly? Valve clearance verified with new valves? What does a compression test indicate?

The BC 272 cams were zeroed with a degree wheel, compression test comes in at 160 all around which historically is normal for that engine.

Have you tried making some adjustments to the VE numbers around the 2500 rpm area? If you're saying the plugs are fouled/wet then this may be part of your problem. I'd also be suspicious of the cam timing if the engine has been apart.

Andre,

I have been adjusting my VE in the cells that I can get access to.

I have triple checked my cam timing and it is bang on.

Could the larger valves have affected my flow characteristics enough to be an issue and have an effect on where I should set my cams?

I would try pressurizing the intake system. To check for leaks and see that the map sensor is reading correctly.

I've heard of aftermarket camshafts (including BC) where the relationship between the cam lobes and the trigger marks for the cam position sensor are offset compared to the marks on OEM camshafts. Offset triggers can cause the ECU to sync in a different location, which can cause the actual ignition timing at the engine to be different than what the ECU claims it should be. Use a timing light to verify that the actual ignition timing on the crankshaft matches that the ECU's reported value for ignition timing, if the ECU says the timing is +30 degrees but the actual timing is -20 on the engine it is not going to run very well.

Thanks Scott,

I have set the trigger with these cam pulleys in the past but it is worth revisiting just in case something has changed .

Nigel, I actually pulled the intake off to eliminate any restriction but as it is MAP sensed and the fault is in the vacuum areas of the map I don't think it is likely to be a boost leak issue.

I have been going through some of my old log files to try and get a hint of what is going on.

The engine is finally running properly.

I rechecked the trigger reference point which was a couple of degrees retarded which partially helped with the issue.

Their was still major amounts of hesitation in that area of the map. I advanced the timing about 10' extra in that area and it now revs past it.

It is interesting that the ignition map that was working previous to having fitted the larger valves would not work. Seems I have a lot to learn about air flow in engines.

I'm glad you have the engine revving at last. It would surprise me if the timing needed such a dramatic change just to get the engine to rev though. Have you confirmed the base ignition timing is correct?