SR is misfiring hard and sputtering under boost need help ASAP!

[dzlpwr]

Just got the sr out of my hatch and into my coupe and now running. It idles fine and free revs fine but under even 1/2-3/4 throttle it will start misfiring and sputtering real badly to the point where I just let out. No boost leaks and MAF plug is good and everything... also if I stay super light on the throttle I CAN get it to rev up all the way but just have to be real light on the throttle. Threw new plugs in it today to see if it would help but no go on that. Pretty much a stock sr with just an exhuast and a PBM mid-mount with no bov. Any help would be great cause I'm trying to get this thing running right and on the track pretty soon!! Thanks!

[traxx07]

Sounds like the fuel pump. Check that and the fuel filter to make sure it's getting the right pressure it needs. Especially under boost.

Have had this happen on a lot of SR's then just popped in the Walbro and viola!

[dzlpwr]

Has a walbro in it already with all brand new fuel lines and a brand new fuel filter... so I doubt its that but no way to know for sure??

[dzlpwr]

sorry for the dumb question but whats the best way to check the fuel pressure??

[Krewlkid]

timing and tps, set back 15* and .45
had the same problem a little while ago

[dzlpwr]

.45v for the tps? and was going to do the timing today until the valvecover nuts didn't want to come off so I guess I have to figure that bs out first. I feel like its a timing issue but I won't lie, I am new to sr's

[nassin31spr]

Timing and check the spark plugs, gap exc. It could also be a boost leak or faulty maf sensor or wiring. Make sure you pressurize the intercooler piping. Just because the couples are tight dosent mean they are not leaking.

[rb25_s13*CHUKI]

Do u have a boost gauge? that would help see if it's a boost leak but it would have to be pretty bad to do that for a boost leak so the gauge will def let you know if it's that. If it's a small boost leak the gauge might drop like 1 psi vacuum but that won't make it sputter like that.

Check the plugs and the gap, change the fuel filter, Post a picture of how the cas is positioned and if u can post pics of the cam timing before you make any changes, also could possibly be the maf but most times a bad maf wont let you rev past 3.5k could be messing up though,

[rb25_s13*CHUKI]

P.s no offence but Pbm mid mount is a waste of money and hurts cooling on your car.

[sdrmiami]

CAS... replace it and your good to go..

[dzlpwr]

Guess I'm going to check the timing... just have to deal with getting the valvecover nuts off because it seems like most of them just want to spin and the nuts don't want to come off... I'll take some pics of how everything's set up when I get it apart. and as far as the maf, it will rev past 3500 fine just under light throttle. And like I sad it free revs no problem

[cbcm2435]

do you make a smoke screen when it starts misfiring under boost? mine was doing that and i had two cracked ignition coils, just something to check. also check you ignition harness for cuts and splices, mine had like 8

[dzlpwr]

Coilpacks didn't looked cracked or anything, and the harness is all good. It's a fresh harness, and no it doesn't seem to really smoke or anything

[codyace]

If it idles and you free rev does it rev fine?

And it only breaks up underboost or load?

I'd recheck to make sure you don't have vacuum leaks.

If the CAS was bad it would have a hard time starting/running, if the MAF was bad it would be in limp mode/throw a code/not start

[dzlpwr]

Yes, it free revs fine. sometimes it will break up or pop a little while free revving it but for the most part it will free rev all the way up no problem at all.

[KiLLeR2001]

Probably coilpacks. When one of mine went I would only have issues past 4.5k, not noticeable when free-reving either, only when in boost. Also check your plugs its a good indication of whats going on.

[dzlpwr]

put new plugs in. The plugs that were in there actually didn't look bad... maybe a little black/burnt if anything but they really weren't bad

[KiLLeR2001]

Stock SR plug gap is 0.036". But like I said, it's most likely a bad coilpack.

[dzlpwr]

whats the best way to actually test a coilpack without just throwing parts at the car?

[KiLLeR2001]

It's hard to test if it only happens under load... If you had a rough idle you could unplug each coilpack individually until the one you unplug results in no change.

Luckily for me I had a friend with a good set of coilpacks so I switched mine with his, drove my car around and no more sputtering / misfiring. Handed him back his coilpacks put mine in drove home and ordered a set for myself.

[dzlpwr]

Ok. Yeah it idles clean and I tried unplugging each (had my buddy hold it at like 1500rpm) and could hear a difference after unplugging each one. So if they are bad it must only be under load

[Asuka]

A friend of mine was having the same problem, so we changed the fuel pump and filter at first and it didn't help. Later on we changed the fuel pressure regulator and that fixed it right up.

[steve shadows]

whats the best way to actually test a coilpack without just throwing parts at the car?

You need to check the resistance of each coil pack with a ohm meter or volt meter set to ohms. Check for consistency between each coil pack if one is way off then that's the bad one in most cases.

Also make sure your coil pack harness is grounded properly to the back of the head and the firewall. This is very important as well.

Make sure your plugs are gaped at .030 or lower for under boost

Check your CAS wiring and plug make sure there are no wiring shorts for sign to the TPS, the CAS the coil packs or the MAF. Check your MAF condition as well.
Check for boost leaks.

A lot of things can cause a break up under load on our cars.

[dzlpwr]

Thanks for the advice guys! hopefully I can look into it more this weekend. I'm gonna check the TPS, clean the MAF, set the idle up perfect, gap the plugs, and then test the coil packs and see if I can get anywhere with this thing...

[steve shadows]

Thanks for the advice guys! hopefully I can look into it more this weekend. I'm gonna check the TPS, clean the MAF, set the idle up perfect, gap the plugs, and then test the coil packs and see if I can get anywhere with this thing...

Be sure to actually check the wiring out. I am leaning towards wiring.

It's almost always some dumb wiring issue or bad wiring harness on S chassis.

[dzlpwr]

I'll double check the ground for the coilpacks but the wiring harness was just re-done professionally and the car had the same problem before the harness was re-done. So I'm assuming its not wiring related. Basically I had this motor in my hatch for awhile then put it in my coupe but with a re-done harness and a painless chassis harness so my wiring is pretty simple.

[HIGHFIVEBETA]

Story of my life.. Does the sputtering increase once you up the boost more?

[dzlpwr]

It gets real bad as soon as it gets into the boost so I just let out... not like Im driving it far anyways... just around the neighborhood testing it out cause its a not registered or insured track car...

[johnbureezu]

Did you ever figure out what the problem was? I have a very similar situation with my SR.

[gostrider]

Bump me too

[stephens14sr]

i had the same problem recently. got a new fuel pump, redid the timing, and got new plugs and gapped them down to .021 now it runs great.

[Jesse SR20]

Are you sure it's not a boost leak ? It certainly sounds like one.

You say there isn't a leak, but how did you test for one ? Did you pressure test it, or just look at it ? You can't visually inspect for boost leaks.

[Midnight Shift]

SORRY for reviving a thread that was a few months old! I had the SAME thing happen to my car for over a year, I couldn't figure out what it was. I then had an engine knock so bad, that I replaced my SR.

Even with the new engine, when I would get into boost, it felt like it wasn't getting enough fuel, or like a boost leak. so I did boost leak tests, tried different MAFS, TPS, Coils, etc! I even changed the fuel pump! Recently it was getting really bad, especially on a not-so-smooth road! It would sputter and almost die out on me!

My friend told me he had the same problem about a year ago. What it turned out being was the ground on the fuel pump. I wasn't being grounded well enough caused it to not allow the fuel pump to run at full capacity! So, I just sliced in a wire and grounded it straight to the chassis, and my car was boosting and running like it's never run before!!!!! Try it out! It is the Black/white wire in your trunk that leads to the fuel pump!

So, 1 wire cost me a new fuel pump, and an engine swap!:fawk2:

Apparently, this can be a little bit common on S13s (I have a coupe!) So, give it a try, it can't hurt to do so!

[Selivince]

Hi, just wondering if this Problem ever got solved? As I'm having the Exact problem on my S14

[ultimateirving]

Hi, just wondering if this Problem ever got solved? As I'm having the Exact problem on my S14


Coil packs, spark plugs and gap size or fuel pump. These seem to be the common culprits. What have you tried ?

[jedi03]

really sounds like boost leak to me...had hose pop off goin onto the freeway and acted like this...no boost, could accelerate just fine...hit boost, sputtering drop in power etc...