New fuel pressure regulator low idle

Laruccia · Jul 21, 2017

Guys, im a newbie when it comes to engines... so i would love some help on this case...

Recently i have my mec convince me that it was a good idea to swap my OEM STOCK fuel regulator for a adjustable fuel regulator... Anyway, this is what we did:

1- removed the old fuel pump and put in a new one (which was meant for a S10, blazer and so on) which produced 4.2 bar of pressure.
2- redid the fuel line and added a blocker so the fuel pump could maintain the pressure and start right away from one day to the other.
3- added a adjustable fuel regulator and set the fuel pressure to 2.7 bar
4- added a new blow off valve (removed the OEM stock)

Now my car is idle at about .750, and when i rev up (with the car at neutral) the rpm drops to about .100 or depending the case it will cut off the engine.

He did tell me that the problem has nothing to do with the fuel line/sistem which he made, but instead it has to do with the blow off (which was an add on to it, since it cut of the return from the original stock valve) so now he needs to adjust the fuel intake so it can compensate for the loose of the return... does this makes any sense? please HELP

Jacolu3 · Jul 21, 2017

Are you recirculating the new bov? If not that could be your problem if you are using a maf.

A Sharp · Jul 21, 2017

I highly doubt the bov is related to the issue. How are you revving it? Are you bouncing it off a rev limiter or just doing some mild free-revs? A gentle free rev isn't even going to open the blow off valve significantly.

A car that wants to die coming off a rev is usually lean, according to Jafro anyway. Venting the bov will make the engine run rich whenever it opens, which is just the opposite.

I would suspect that you have a vacuum leak or that your fuel pressure isn't actually set correctly. Did you set the fuel pressure with the fuel pressure regulator's vacuum line disconnected?

A Sharp · Jul 21, 2017

Also 2.7 bar sounds low. I think base fuel pressure should be 3 bar, if I've got my unit conversions right.

Laruccia · Jul 24, 2017

Jacolu3 said:
Are you recirculating the new bov? If not that could be your problem if you are using a maf.

Thanks for the reply. Nope, the bov is not been recirculating, he blocked the entrance of the return for the stock valve to the intake. The bov just spits it out.

pauleyman · Jul 24, 2017

Laruccia said:
Thanks for the reply. Nope, the bov is not been recirculating, he blocked the entrance of the return for the stock valve to the intake. The bov just spits it out.

Recirculate bov. That is your problem

Laruccia · Jul 24, 2017

A Sharp said:
Also 2.7 bar sounds low. I think base fuel pressure should be 3 bar, if I've got my unit conversions right.

Thanks for the reply, well iv found that the stock fuel pressure is around 2.7 to 2.8 bar, not more, not less, so im not sure if it has to do with that... The car rans smooth, just in the cold ending it struggles to accelerate... but after a few minutes it reaches idle temp and it runs fine... My mec insists that the problem has nothing to do with the fuel pressure... that the problem comes from the bov... since we made the change at the same time, i can't really say if it is or not the bov fault... It does makes sense that since there has been a cut in the return gasses from the stock bov, the car now runs a bit lean... but shouldn't that affect my performance?
i did see in fact a better response to the throttle... im gonna try to post a video at idle when i rev it so u can have a look.. Thanks for the help!

Laruccia · Jul 24, 2017

pauleyman said:
Recirculate bov. That is your problem

how to recirculate it when using a atmospheric bov?

Laruccia · Jul 24, 2017

just an add on, he wants to regulate the air intake... im not sure if he will do the proper way (by the ECU) or what ever other way there is... any one have an idea if it would be better to just go back to the stock bov?

pauleyman · Jul 24, 2017

For now go back to stock. Don't buy bov that doesn't recirculate.

Laruccia · Jul 24, 2017

pauleyman said:
For now go back to stock. Don't buy bov that doesn't recirculate.

Thanks man, ill go back to stock...

TurboTesh · Jul 24, 2017

For the FPR, 2g turbo fuel pressure is 43.5 baseline +- a point or so. With the car running, pull the vacuum line and put your finger over the regulator nipple and set it to 43.5psi (3 Bar). Then put the vacuum hose back on and it should drop a bit.
As for the BOV, definitely recirculate until you go speed density or run a GM Maf.

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