It doesn't want to go over 100 mph

[PlymouthBarracuda]

Hi there, could you please help me find the correct fuel pump?

About a year ago, I installed the MU1959 (mainly because of the new fuel filter), but now I've noticed that the car struggles when I go full throttle above 100 mph — there are some "hesitations" and a noticeable loss of power (Especially in S (M) transmission mode).

Interestingly, when driving gently, it can still reach 136 mph without issues.

Someone suggested the fuel pump might be the problem, even though the OBD2 shows 43 psi on idle.

The MAP sensor, spark plugs, and oxygen sensors are all new. Gasoline 92 AKI

Would the CARTER P76848M be a good option in this case?

[CamaroCracka]

Not sure on the fuel pump part numbers, but I'm pretty sure fuel pressure should be 58psi all the time, more if you are boosted.

Why not just get a ZL1 pump and call it a day. They work great.

[gtstorey]

Fuel pressure should be at 58 psi. If you can read your obd data, what are fuel trims doing? But you don't want to do much all out pulls since this sounds like it might be just lean enough to hurt something.

Was this pump an Amazon or eBay purchase?

[gtstorey]

And where did you source the "new sensors"?

[PlymouthBarracuda]

Originally Posted by gtstorey

Fuel pressure should be at 58 psi. If you can read your obd data, what are fuel trims doing? But you don't want to do much all out pulls since this sounds like it might be just lean enough to hurt something.

Was this pump an Amazon or eBay purchase?

Hi, the fuel trims are perfect—slightly rich. I don’t have catalytic converters, and the ECU was tuned, which is probably the reason. I bought it from RockAuto, as usual. The label has an ACDelco badge on it.

I will try ZL1 MU2101 pump then, rockauto suggest good price

[PlymouthBarracuda]

Originally Posted by CamaroCracka

Not sure on the fuel pump part numbers, but I'm pretty sure fuel pressure should be 58psi all the time, more if you are boosted.

Why not just get a ZL1 pump and call it a day. They work great.

I will try ZL1 MU2101 pump then, thanks !

[PlymouthBarracuda]

Originally Posted by gtstorey

And where did you source the "new sensors"?

There also at rockauto, original GM 2134408. Previously, my spark plugs were covered in black carbon, although according to diagnostics, the sensors were normal. After replacing the spark plugs are only slightly black

[bsn]

If you are seeing any black on your plugs you are running way too rich-at least with U.S. gas maybe they use different additives in the U.K. Do you have an actual data log you can share? It does sound like a fuel starvation problem which could be the fuel pump, the strainer in the tank or injectors but it could also be something in the tune. It would be interesting to see what your spark advance looks like under load-I wonder if it's pulling too much timing.

[acammer]

Has this been a problem since it's been tuned, or is this a new issue? In either case, if the car is under heavy load and doesn't want to accelerate, get out of the throttle! That's a great way to tear stuff up.

Fuel trims won't be affected under Power Enrichment (heavy throttle) so those won't give you any sort of useful indication on what's happening with fueling under those conditions. Likewise, spark plug reads are really only useful on fresh plugs, and only if the engine is cut-off immediately after marking a pull. Any idle/cruise time on the plugs will quickly erase any meaningful information from a preceding pull.

[PlymouthBarracuda]

Originally Posted by acammer

Has this been a problem since it's been tuned, or is this a new issue? In either case, if the car is under heavy load and doesn't want to accelerate, get out of the throttle! That's a great way to tear stuff up.

Fuel trims won't be affected under Power Enrichment (heavy throttle) so those won't give you any sort of useful indication on what's happening with fueling under those conditions. Likewise, spark plug reads are really only useful on fresh plugs, and only if the engine is cut-off immediately after marking a pull. Any idle/cruise time on the plugs will quickly erase any meaningful information from a preceding pull.

Yes, this is a new issue. I will replace the pump

[PlymouthBarracuda]

Originally Posted by bsn

If you are seeing any black on your plugs you are running way too rich-at least with U.S. gas maybe they use different additives in the U.K. Do you have an actual data log you can share? It does sound like a fuel starvation problem which could be the fuel pump, the strainer in the tank or injectors but it could also be something in the tune. It would be interesting to see what your spark advance looks like under load-I wonder if it's pulling too much timing.

I will provide it as sson as I visit my diagnostics guy ) i will reply you here

[1JEWLDSSRS]

Originally Posted by CamaroCracka

Not sure on the fuel pump part numbers, but I'm pretty sure fuel pressure should be 58psi all the time, more if you are boosted.

Why not just get a ZL1 pump and call it a day. They work great.

This is what I did when I had to replace my pump, before I was even cammed. Great upgrade.