RB20 sputtering at all rpms

[wrgibson]

I've got a problem with my RB20 sputtering at all rpms. The problem isn't so apparent when SLOWLY free-revving the car, but if I stab the gas it has a lot of trouble revving up because it is sputtering so badly. The car has new Super Spark coils from Raw Brokerage, a walboro pump, nismo fpr and a j30 ignitor. Otherwise, the car is stock. I just put the ignitor on it tonight thinking it was the problem but it didn't help. I'm beginning to think my fuel pump is crapping out. On the road, the car does ok if it's not under load (downhill, cruising, etc). Any time it's under the slightest bit of load it sputters. If I try to throttle through the sputtering while driving the afr's climb up from about 16 to about 19. I've got about 39psi of fuel pressure at idle with the vacuum line on. When I free rev it and look at the fuel pressure gauge it doens't get much past 45psi....I'm only revving to about 3000rpm, by the way. The fuel pump is hard wired to the batt. through a relay. I've yet to check voltage at the pump or replace the fuel filter, but I'll do that tomorrow. I feel like the fuel pump is the problem, but I could use some help figuring out this problem.

Thanks!!

Through some research I think the following could be possible sources of the problem:
Fuel pump
CAS
MAF
Clogged injector or fuel filter

[RustspecS13]

I had a problem like that last year, and the slower/smoother i revved it the better it was. Turns out my j30 ignitor was bad, and I had just swapped it about a month before.

Are you running a stock fuel pump? I did for about a week, and it only cut out out at high rpm/boost. Other wise it was fine.

~Alex

[wrgibson]

I just got the ignitor used off ebay, so there is a chance that it is bad. Although, if the ignitor were bad woudn't my wideband being reading rich due to all the unburned fuel from the weak spark?

I'm running a walbro pump....hardwired.

[RustspecS13]

I had a problem like that last year, and the slower/smoother i revved it the better it was. Turns out my j30 ignitor was bad, and I had just swapped it about a month before.

Are you running a stock fuel pump? I did for about a week, and it only cut out out at high rpm/boost. Other wise it was fine.

~Alex

[Cjmartz2k]

I just got the ignitor used off ebay, so there is a chance that it is bad. Although, if the ignitor were bad woudn't my wideband being reading rich due to all the unburned fuel from the weak spark?

I'm running a walbro pump....hardwired.

If your engine is missing do to an ignition problem, the wide band will actually read lean, not rich. Counter intuitive I know, but it measures the ratio of 02 in the exhaust, so when a cylinder misses, yes, extra fuel gets into the exhaust, but so does a much larger percentage of 02.

[wrgibson]

Like I said in my OP, if I try to throttle through the sputtering, my wideband reads up to about 19-20, which could mean an ignition problem. If I have new coil packs and a used J30 ignitor that "should" be working that only leaves the CAS, right? If the problem is fuel related, which I'm beginning to think is the case, it could only be the pump, filter or injectors. I suppose it could be the fpr, but my fuel press. gauge reads about 39 at idle and only about 45 at ~3000 rpms.

I think the pump may be doing well enough at idle and extremely low load conditions to allow the car to run, but when any load is applied the pump can't keep up. It is a walbro unit that I put in the tank about 2 years ago. I heard somewhere that the fuel in the tank is what helps to cool the fuel pump. I almost always have less than a quarter tank....could this have helped cause the pump to fail after only 2 years?

Any input is appreciated.

[wrgibson]

Just got done working some more on diagnosing the problem....the car sputters real bad when stabbing the gas and free revving. If I slowly free rev the car it does just fine. I'm beginning to think it's fuel related. Now, I thought I remember seeing somewhere on the internets that a person can clamp off the return fuel line to check for a failing pump. Well after putting a small worm clamp on the return line and restricting it down until fuel pressure came up to about 42psi at idle, the sputtering seems to have gone away.

Has anyone else ever heard of this trick to check for a bum pump?

[julio]

Just got done working some more on diagnosing the problem....the car sputters real bad when stabbing the gas and free revving. If I slowly free rev the car it does just fine. I'm beginning to think it's fuel related. Now, I thought I remember seeing somewhere on the internets that a person can clamp off the return fuel line to check for a failing pump. Well after putting a small worm clamp on the return line and restricting it down until fuel pressure came up to about 42psi at idle, the sputtering seems to have gone away.

Has anyone else ever heard of this trick to check for a bum pump?

Couldn't you have just adjusted your fuel pressure with the nismo fpr to check this?

You said that your pump is hardwired, I would check to see what voltage your fuel pump is getting since you were messing around with the wiring. Your ground may be poor and the pump is getting the proper voltage. Is that walbro you installed new or used?

[wrgibson]

Yes, I could have simply raised the pressure at the rail via the fpr. However, I read somewhere, SAU I think, that clamping the return line is a method of checking for a failing pump, so that's what I did.

The pump is getting ~13.8 volts at idle and while revving. The walbro was new when I installed it ~2 years ago.

[RustspecS13]

yes constantly driving with 1/4 tank will kill a walbro in a short time, I always try to keep mine above 1/4 at all times. Usually it try to fill it up every time it got down to 1/4tank if not at least up to 3/4 a tank. That's because the pump has bushings, not bearings, and it uses fuel to lubricate and cool the pump.

~Alex

[R32ONP]

sounds to me like ur fuel pressure isnt set properly bro wat psi have u got it set to with the vac hose off?

[wrgibson]

~43psi with the vac line off.

Alex- I'm thinking that I killed it. Like I said, I rarely have any real amount of gas in the car. I drive it so damn much that it's always empty. I ordered another walbro....hopefully that fixes it.

[wrgibson]

After replacing the walbro it ran a bit better, but basically no change. I took the fuel filter off and the gas that was coming out of it looked the color of rust. I replaced the filter and the car ran like its old self for about 2 miles. The first time I tried to get into the boost it started sputtering hard again. Now it's sputtering again with intermittent spurts of it running good. I doubt the fuel was dirty enough to clog the new filter up that fast. Considering how dirty the fuel filter was, I'm thinking that one or more of the injectors could be clogged.

Would dirty/clogged injectors cause the motor to sputter?....it almost feels like the same sputter as when the coilpacks were going out.

[RustspecS13]

Sounds like you have a rusty tank, i had issues with rust in my old tank even with my NA KA cut out at WOT/drifting some times.

I went through 4 fuel filters while i was cleaning that tank/getting a better one.

~Alex

[wrgibson]

I removed the fuel filter again today and the gas coming from either end looked to be clean. I can blow through the filter also. After replacing the fuel pump, filter and ignitor, the problem has now become less consistent. Sometimes it'll rev clean, other times it sputters. It ALWAYS sputters when I get to about 5 psi of boost. I can hear each of my injectors clicking by placing a screwdriver on them and my ear. I know the "new to me" J30 ignitor could be bad, but is there anything else I'm missing?

When I unplug the MAF the car dies.....this leads me to believe the MAF is working.
Fuel pump is brand new.
Fuel filter is brand new.
Coil packs are brand new.
Fuel pressure is ~39 at idle w/ vac line ON.
Vac at idle is ~16-18.....it has always been low.

Could it be that one or more of my injectors are clogged? I don't think it would run sporadically better if an injector were clogged.
How about the coolant temp sensor? If it were going bad would it cause symptoms such as a random sputter?
Maybe a bad ground somewhere? But why would the car suddenly run like poo, then run a bit better with new fuel system components if a ground were bad?
Timing? My base timing is set at about 16* as per something I read on the internets. I don't think it's the timing because it is set the same as it has always been.
I know I have a small boost leak at the throttle body, but it has always been there so I doubt it has just now started causing a problem.

My diagnostic skills are typically pretty good but this time I'm stumped.

[RustspecS13]

Fix all your boost leaks, then try again.

~Alex

[R32ONP]

yes deffinatly fix the boost leaks as that will only cause problems...injectors could be blocked/clogged so fix the boost leaks first and try it and report back about it

[wrgibson]

Boost leak test complete.....no leaks except for the small one at the throttle body. The car has always had this leak and it was running fine for about 2 years. The car acts like a coil is bad. It sputter under mild load and also at about 5 psi. The sputtering is intermittent....it'll pull good until 5 psi then sputter, then it'll run like poo at all rpms for a second, then it'll act better. I checked the ignitor as per the FSM and it passed. The coils were new when I bought them about 6 months ago. I've yet the check voltages at the MAF and CAS. I'm thinking one of them is on the way out....or maybe the coolant temp sensor.

[wrgibson]

After cleaning the MAF again and double checking that the wiring is ok, the car is beginning to get better. There is still a slight miss at idle, some sputtering at very low rpms that clears up as rpms come up and a hard sputter at about 10 psi. I'm thinking the high RPM sputter is a coilpack. I have superspark coils on the car now but it feels EXACTLY as it did when I had a stock coil crapping out. I guess one of the SS coils went bad. I've heard some aussie guys have trouble with them too.

My question is, would a failing coil also cause the low rpm sputter?

[R32ONP]

it can cause a miss on idle...sometimes...sometimes they can idle fine and miss on full load...have u checked ur timing??? and is there no fault codes???