Sign of a bad fpr

[frankydodo]

Hey guys i just finish installing my ffp on my rb20

The first day everything was fine and my a/f was 10-11.5 at wot all to way to 7k rpm

Yesterday i adjusted my tps as close as i can to 0.5v closed like the fsm said. I did a test ride and everything went good!

But now my a/f is always changing in cruise . It jump from 10 to 15 to 13 to 14 to 12 always. In boost also its jumping alot so i'm not boosting at all to be safe.

Fuel pump is new
Fuel filter is good
Injector also

Could it be the fpr? I hooked the vacuum source for the fpr directly to a vacuum on the manifold. But on stock im its connected where there is the bleeder so is there a kind of restrictor or so?

Or what else can make the afr jump like that? Maybe a exhaust leak before the sensor?


Other option could be the o2 sensor maybe?
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[speedfreak]

You should watch your tps at cruise they can fluctuate 10% up and down with a steady foot and cause the ecu to react as if your accelerating and letting off which messes with AFRs.

[frankydodo]

Good ill ask someone to step on the gas pedal with ign on and ill check if it jumo up and down then if yes its the tps that need to be replace?

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[Skym]

Stock ECU can switch between knock maps, main maps when it detect's knock or not. The A/F ratio can change because of that when on boost. Off boost it's most likely the o2 sensor + ECU adjusting A/F ratio which is normal (it's not normal when readings from o2 sensor slowly fluctuate and engine runs excessively rich). If switching between knock, main maps it might indicate engine needs a retune with Nistune or aftermarket ECU.

Stock FPR can be checked via T'ing in a fuel pressure gauge inbetween FPR, fuel filter. Should get 35.5psi at idle with vacuum hose to FPR connected (with factory fuel pump, fuel pressure should be higher with aftermarket fuel pump installed). If remove vacuum hose to FPR (block nipple on intake plenum with thumb or similar to stop it leaking), fuel pressure should rise 7.1psi or so and engine stumble a bit. If diaphram inside FPR is damaged, fuel pressure should stay the same.

Also make sure you have hardwired the fuel pump, as voltage could be dropping to 10 volts thus fuel pressure drops when on boost.

[frankydodo]

Good news guys!

After the plenum installed i needed to make longer wore for the tps. When i solder them it was a little dark and i didnt realise that the signal wire is actually a shielded wire. (A wire with a foil and a ground wire all around.)

So i soldered a normal piece of wire but when i cut the original shielded wire the shield ground was no more grounded and i think it was making contact with the signal wire( yep very bad i know)

So! Tonight i bought a meter of the shileded wire , soldered it to the signal wire and ground the foil to the body and guess what?

The more i press the gas pedal , the more the a/f ration gets lower! So happy its a big relief because i store the car soon!

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