S14 KA24DE - Loss of power and poor mileage

[eternaldrake]

Fairly new to the 240sx, have had one as my DD for about 6 months now, an S14 with 147k. It was running great up until recently, after a trip to New Orleans, it began to run awfully and my mileage dropped from ~22-24 down to ~16-18, depending on how I drive it.

In detail, it had rough idle, awful acceleration, and little power. I cannot accelerate past 25 mph going uphill.

So far I have replaced: spark plugs+wires, distributor cap+rotor, MAF sensor, TPS, O2 sensor, and fuel filter.

My first suspicion is a weak fuel pump and I was thinking about just putting in a Walbro 255, but that doesn't explain the drop in mileage. I was thinking possibly fuel injectors also but I do not know how to go about checking them.


I've tried searching this issue as thoroughly as I can on here and other sites, but I was hoping to get some help from you guys if possible.

[frabus]

Have you tried checking all your grounds? You should check for any codes from the ecu.

[eternaldrake]

I haven't checked the grounds yet, I'll check the ECU in the morning for codes. The process to do so should be the same as in here (http://www.ka24development.com/ecu_codes.html) right?

[frabus]

Yea that's it right there. Also the fsm helps to find all the ground wires.

[Butcher240sx]

Try the cylinder head temp switch and the knock sensor. But try the sensor first.

[rcdad123]

definitely check the knock sensor and the cat. converter if the car has one. if the knock sensor is bad, the computer will retard the ignition timing and add extra fuel for "safety reason". that will definitely loose a lot of power and use more fuel. if the cat is getting really hot, almost glowing, it`s either clogged or the engine is having a really bad ignition misfire and a lot of the unburned fuel is igniting in the cat. pull the spark plugs out and compare them to each other. if you have one that does not look the same as the other ones, the cylinder that it came out of has a problem, either misfire due to a really low compression or a leaking fuel injector. good luck

[s13-LBC-562]

had same problem with my s13 ka24de but i change all sensor,fuel filter,fuel injector,distributor and cap+rotor and i was getting better mpg.20 dollars of 91 last me 4 day of driving 26 miles back and fourth from work

[Bentleyness]

on the two s13 i had i ran the expensive gas 93 for me and the engine ran better and it had better mileage then regular gas did, from my personal ex.

[shift_down]

You can't use a walbro unless you tune for it because it puts out more lpm than stock fuel pump.

Did you check for codes yet?
With the engine running, does the engine shake?
What is your idle rpm?
Post pics of your spark plugs.
Do you have a fuel pressure gauge?

Pull each spark plug wire one by one and see if the engine makes a different sound. If you hear and feel the engine noise change with each wire, then your injectors are good(in your case).

[nismoracingsx]

OP, you can check for a dead injector by testing resistance between the two pins on each injector. Can't quite remember, but mine are normally like 10-12 ohms, and when one goes bad it'll be much higher and easy to spot.

Quit throwing parts at the car. :p

Check the compression on all four cylinders and see what numbers you get.

Check to see what voltage your internal coil is seeing at the connector on the distributor.

Check timing yet?

[Alamo_City_210]

You can't use a walbro unless you tune for it because it puts out more lpm than stock fuel pump.

Yes you can. That's the purpose of the FPR.

[shift_down]

Really? Learn something new every day.

[Alamo_City_210]

Yeah. I thought that at first as well but on the Walbro site, it says the same. The excess would just be rerouted back to the tank.

[eternaldrake]

Hey there, I've been really busy with school and work so I haven't had time to do much, just wanted to check in with what I have so far.

This morning I pulled codes from the ECU and the only code its throwing is 105, which is for a bad EGR.



definitely check the knock sensor and the cat. converter if the car has one. if the knock sensor is bad, the computer will retard the ignition timing and add extra fuel for "safety reason". that will definitely loose a lot of power and use more fuel. if the cat is getting really hot, almost glowing, it`s either clogged or the engine is having a really bad ignition misfire and a lot of the unburned fuel is igniting in the cat. pull the spark plugs out and compare them to each other. if you have one that does not look the same as the other ones, the cylinder that it came out of has a problem, either misfire due to a really low compression or a leaking fuel injector. good luck

OP, you can check for a dead injector by testing resistance between the two pins on each injector. Can't quite remember, but mine are normally like 10-12 ohms, and when one goes bad it'll be much higher and easy to spot.

Quit throwing parts at the car. :p

Check the compression on all four cylinders and see what numbers you get.

Check to see what voltage your internal coil is seeing at the connector on the distributor.

Check timing yet?


Yea one of the issues I've been thinking it might've been is a clogged catalytic converter. To check that do I need to just remove the cat and inspect it? Also re: spark plugs, when I changed them out, the plug for cylinder 1 was fouled out really bad. The old spark plug wires were a bit too small and the plug for cylinder 1 would pop out pretty often so I figured it was just that, but I'll check the resistance on the injectors next. Also, how do I check the timing?

Finally, regarding the EGR code. I was thinking I should just clean out the vacuum tubes going to it myself and if it continues to throw a code whether I should disconnect it entirely or get the EGR replaced. I've read a bad EGR can cause poor mileage which is part of my problem, but that alone wouldn't explain my poor acceleration would it?