Any ideas whats causing this

[Richie-Van-GTi 74 2 Cars]

Car idles great at 14.6-14.7 afr, above 3k its great, from 2-3 k its very hesitant, misfiring and generally embarrassing to be near.

Spark plugs are all black on one side only.

Its been on the rollers 3 times and they cant find anything wrong with timing or fueling. Its now had coil pack, leads, ignition amp, injectors and plugs. Fpr is new and pressure has been tested etc.

Driving me crazy as I just want to drive it.

1.6 8v gti, 11:1 CR, piper 275 cam, 4 branch manifold, 60/2 billet flywheel, adaptronic E420 ecu, map sensor, throttle potentiometer, 200cc injectors, wideband lambda and mapped as map vs rpm

Edited Friday at 06:19 PM by Richie-Van-GTi

[Thijs_Rallye 89 4 Cars]

Is it hesitant between 2k and 3k @ wot? Or part throttle? Did they only map the high load cells or also the "zero" load cells in the calibration? Does it run open or closed loop in that part? There are a lot of factors in play, especially with a cammed engine. Cammed engines and map sensors do not always play nice afaik.

 

Looking at the plugs it appears to run pig rich. What heat range are they?

[Richie-Van-GTi 74 2 Cars]

49 minutes ago, Thijs_Rallye said:

Is it hesitant between 2k and 3k @ wot? Or part throttle? Did they only map the high load cells or also the "zero" load cells in the calibration? Does it run open or closed loop in that part? There are a lot of factors in play, especially with a cammed engine. Cammed engines and map sensors do not always play nice afaik.

 

Looking at the plugs it appears to run pig rich. What heat range are they?

Hesitant at any throttle range other than steady rpm, all open loop, not been able to get it running well enough to test closed loop. Map readings look fairly steady throughout the range.

Plugs are ngk bcpr6es, tried 7s as well

[petert 603]

So hard to diagnose from the bus I’m on, but first thing I’d do is make it idle at 13 to 13.5.

[petert 603]

Are you sure the wideband is correct? Idling an engine with a bigger cam at 14.7 seems foreign to me.

[Richie-Van-GTi 74 2 Cars]

9 hours ago, petert said:

So hard to diagnose from the bus I’m on, but first thing I’d do is make it idle at 13 to 13.5.

Sounds very rich for idle, would expect that at high rpm.

9 hours ago, petert said:

Are you sure the wideband is correct? Idling an engine with a bigger cam at 14.7 seems foreign to me.

Yes wideband is correct, he tested everything and validated the figures with his standalone equipment while mapping.

Only parts that weren't reliable were knock sensor which is not being used now and the idle control (mi16 pwm type) which is now converted back to a standard SAD system.

[petert 603]

Idle AFR can be difficult if you don't have a sensor in the oem position, as there isn't enough flow. How did you set the idle AFR? Is there a zero throttle map, which overrides the MAP sensor?

[Richie-Van-GTi 74 2 Cars]

No override, it just uses map vs rpm throughout. Idle isnt an issue though, its just the 2k to 3k rpm range

[Richie-Van-GTi 74 2 Cars]

I did wonder if its the FPR, maybe its pulsing the fuel pressure in that range and would it be better to remove the vac hose on it and just have one pressure throughout? Not sure exactly how they behave normally, I would expect a smooth transition but at what throttle/map range?

[welshpug 1,674]

that may well be an useful place to start, remove any possible variance, is it a fixed FPR bar the vacuum reference?

 

rather odd to be mapping a lumpy cam engine on MAP, typically it would be on TPS if there's chance of uneven or large pulses.

 

this is where your money pays to find a good mapper.

[Thijs_Rallye 89 4 Cars]

3 hours ago, Richie-Van-GTi said:

I did wonder if its the FPR, maybe its pulsing the fuel pressure in that range and would it be better to remove the vac hose on it and just have one pressure throughout? Not sure exactly how they behave normally, I would expect a smooth transition but at what throttle/map range?

I would expect the map sensor to swing even wilder than your fuel pressure because of the intake pulsing. Did they use a separate vacuum gauge during the rolling road mapping session? I wouldn't be surprised if it's harmonics that are ruining the map signal. 

 

Like Peter says, some ECU's have the possibility to run a different load strategy at certain operating points / areas. Or maybe it supports signal conditioning at those areas. That could be a solution if it are the harmonics in the intake.

 

Is the map fitted directly in the plenum or is the vacuum routed to the sensor with a hose? Might be worth a try as well to "throttle"/pinch the hose to hopefully smooth the vacuum signal as a test. 

 

It's all mostly guess work from my side here though, hard to tell without having hands on the vehicle.  

 

[SRDT 194]

When using MAP wit ITBs you need a small plenum to get rid of pulses and I think some OEM have something simimiar on the vacuum hose when the MAP sensor is inside the ECU.

[Richie-Van-GTi 74 2 Cars]

Map sensor is remote on a thin vac pipe, about 4mm ID I think from memory, standard plenum and throttle body but a potentiometer rather than the old school switch.

Its quite an old adaptronic ecu so it doesnt have a load of extra functions for splitting the mapping across the loads etc, its one map or the other. It could be mapped as TPS/rpm rather than map sensor but want to be sure that is the issue first, 2 different mappers have had it and neither commented on the map signal being an issue.

[welshpug 1,674]

Remote mounting the map sensor is fine and not uncommon,  but you do need a firm rubber hose for it, thin silicone is not very stiff.

 

You can also fit a damper inline, zx and 405 used them.

[Richie-Van-GTi 74 2 Cars]

1 hour ago, welshpug said:

Remote mounting the map sensor is fine and not uncommon,  but you do need a firm rubber hose for it, thin silicone is not very stiff.

 

You can also fit a damper inline, zx and 405 used them.

Its a good quality vac line, not soft silicon, quite firm braided pipe.

Will have a look for the damper, thanks