Low Idle after new Fuel Pressure Regulator

[polar ITA]

Hi all,
my Super Polar B200F with LH 2.4, perfectly tuned before, shows a very low idle RPM after I replaced a faulty original Bosch FPR with a Skandix label one (it seems original Bosch is discontinued) and the rubber pipe that link it to the injection rails (gasoline specific pipe, up to 10 bars).

During the job I replaced, too, the air filter, cleaned the airbox and all air intake pipes, checked for leaks, pulled out the thermal switch in the airbox for hot air intake, since I don't need it, and I plugged the hot air intake.

So: what could be the cause for this idling at around 500RPM? It is not bumping but very regular, only drawback is, while driving, sometimes, at stops, the engine shut off, mor often when AC is on.

One more thing I noticed is that pulling up to 5500/6000rpm on the road there is some "hickups"... but this si a minor problem... I never drive over 4000... mostly 3500 5th gear

I ask myself and all of you experts: is it possible that the pressure regulator is not correct in terms of pressure? 2.5bar instead of 3.0bar ? Skandix site does not declare the pressure, it just say it is ok for my car.

Thanks in advance for your suggestions!!!

[Clifford Pope]

What was the trouble with the old regulator? If say the idling was correct before, you could try swapping back as a test. That would at least show whether the regulator is responsible for the low idling, or whether perhaps you have inadvertantly changed something else.

[polar ITA]

Clifford the old regulator leaked gasoline that flowed back into the intake.
Since my car has LPG too, I am afraid I can risk some dangerous backfire.
I forgot to say that idle with LPG is correctly around 800rpm.
Anyway I'll drop an email to Skandix to be sure that this regulator is a 3bar unit.

Originally Posted by Clifford Pope

What was the trouble with the old regulator? If say the idling was correct before, you could try swapping back as a test. That would at least show whether the regulator is responsible for the low idling, or whether perhaps you have inadvertantly changed something else.

[Clifford Pope]

OK, forget that then.

[DW42]

One thing to check carefully is whether with the air box mod you performed is restricting air flow somehow. Did you follow instructions like these? https://www.matthewsvolvosite.com/fo...hp?f=2&t=66714

[polar ITA]

Yes, i did something like that. The only differences are that I reconnected the snorkel to the original fresh air intake and I plugged the warm side with a piece of tire inner tube instead of a proper plug.

BTW I received an answer from Skandix that say, while confirming that the FPR is a 3bar type, it can be due to the "adaptive" feature of the ECU: they suggest me to disconnect the battery for >10 minutes and then drive for at least 20 Km to let the ecu adapt to the new regulator.

Originally Posted by DW42

One thing to check carefully is whether with the air box mod you performed is restricting air flow somehow. Did you follow instructions like these? https://www.matthewsvolvosite.com/fo...hp?f=2&t=66714

[polar ITA]

UPDATE: so it seems to be correct what skandix says. The ECU need some road in to adapt after the FPR swap.
Now idle is ok (both gasoline and LPG, with AC on and off).

One issue still on: the loss of power over 4000... some suggestion for further investigations? a compression test or something related to electrics (distributor, spark plug cables...)
Any advice is very welcome!