engine missing? lack of power

So I had issues with idleling and starting my xj. After a while it wouldn't start.

So I changed the CPS.

Engine starts now.

Prolem is I have a problem with having enough power to go faster then 15 mph. If I floor the gas it almost seems like it is missing. I hear a random pop, but only once.

I have thought the TPS but I replaced that about 6 months ago so I figure its good.

Any suggestions? Is it vacum, is it cam position sensor, or anything else?

What is your fuel pressure?

Don't know how do I check?

Beg/borrow/rent/steal(?) a fuel pressure gauge, attach it to the Schrader valve (looks like a tire inflation valve, only larger) on the fuel rail.

Pressure should be 30, and change to 39 when you disconnect the vacuum from the pressure regulator at the rear of the fuel rail.

BTW--what injectors are you running?

I have never changed the injetors so I assume they are stock but I am not the 1st owner

If they are the original OEM injectors with the metal and plastic bodies that are pressed together, then you should probably replace them as they will be, after 19 years, in fairly poor condition and they tend to leak where pressed together, and that will burn your XJ to the ground.

Do a search for Mustang injectors on here. I am running the Ford organge-top 19 lb injectors and am very statisfied with them. They are one-piece bodies and have four spray nozzles instead of just one. They can be picked up at the salvage yard CHEAP and on eBay too.

While they are most commonly referred to as Mustang, these organge-top 19 lb injectors were/are used on 3.8 engines and up to V8s in F350 vans.

i checked the fuel pressure and i am running 20 psi at idle and full throttle.
i didnt try disconnecting the vacum. but 20 psi is to low anyways.

so now i need to start replacing injectors or fuel pump?

oooh...yeah, fuel pump is dead. Base fuel pressure should be in the 40-ish' range.

CWhiteRun said:

oooh...yeah, fuel pump is dead. Base fuel pressure should be in the 40-ish' range.

Click to expand...

Fuel pump is probably dead, but before spending the big bucks and effort to R&R the pump, change the fuel filter and bypass the white resistor block on the DS fenderwell to see if you get any change. Also, inside the tank between the fuel pump and the assembly mount flange is rubber fuel line that degrades and will bleed off pumped fuel, i.e., pressure.

Try the ballast resistor, fuel filter first, then the in-the-tank rubber fuel line and fuel pump just because you are in there.

And, on the 87 through 95 the correct fuel pressure is 30 psi "base", and 39 psi with the vacuum removed from the regulator.