Sr leaning out and misfiring at wide open throttle

[1988montecarloss]

Just got my car running and driving again a month or so ago and it was running just like it always had 11.5-12:1 afr and no breaking up at high rpm but I let it sit for a couple weeks during my final bout trip and tried it out today and was going 16:1+ lean at anything over 3/4 throttle and breaking up after 4-5k rpm

Haven't messed with it again yet as the car is at my parents house 40 min away but trying to get a list of ideas together to test for when I go back to mess with it

So far I plan on checking fuel psi, voltage at fuel pump power and plugs.

Combo is an s13 sr, s14 t28 bb, 550cc injectors, z32 maf, FMIC and enthalpy ecu tuned for the mods. Fuel pump is also hardwired and has been for the last two years so nothing new there

[tuzzio]

Gotta watch out for this cold air homie. Check the maf, if not, check out your coils. A lot of people go to LS coils (myself included so I can vouch) because the stock SR coils blow.

[cash$addict]

i have the same problems that started after sitting, it only happens on my car when its warm out but I checked the fuel pressure under load to verify the pump wasn't cutting out, I checked all the wiring to the maf from the ecu with no issues, changed the maf, still the same. my cars an hour away so I'm in the same boat. I think its the ECU but I haven't had a chance to change it yet. let me know what you find!

[1988montecarloss]

Gotta watch out for this cold air homie. Check the maf, if not, check out your coils. A lot of people go to LS coils (myself included so I can vouch) because the stock SR coils blow.

Still been 70-72 up here so I don't think the weather has to do with it but I do have a couple sets of LS coils laying around that I've been meaning to wire up and get plug wires for 😅

i have the same problems that started after sitting, it only happens on my car when its warm out but I checked the fuel pressure under load to verify the pump wasn't cutting out, I checked all the wiring to the maf from the ecu with no issues, changed the maf, still the same. my cars an hour away so I'm in the same boat. I think its the ECU but I haven't had a chance to change it yet. let me know what you find!

Will do man hoping to have some time to mess with it tomorrow

[1988montecarloss]

Checked fuel pressure and all fuel pump wiring, car makes 13.9-14 volts while running and that's what the pump sees, fuel pressure is at 43psi

Going to swap out the fuel filter and soft lines tomorrow will update then

[kenfuji]

is it possible your CAS got loose/moved and messed your timing?

[1988montecarloss]

is it possible your CAS got loose/moved and messed your timing?

Yeah I gotta get a timing light to make sure it's set right and also gonna try swapping another set of 550 injectors I have in and build a boost leak tester

Swapped out fuel filter and lines today but made no difference

[jr_ss]

I suspect bad fuel. Have you added octane booster or stabilizer? Fresh gas may cure your problems.

[OutlawLui]

Don't forget to check the tps voltage open/closed

[ZenkiZenki14]

Hmmm, Mine was MAF wiring. Was corroded in some spots. If I pulled on the harness, it would cut out to the point of almost dying, in some cases it would and ran super rich. But you said you checked yours so that's out. Maybe clean the IACV and check TPS voltage as well.

[1988montecarloss]

I suspect bad fuel. Have you added octane booster or stabilizer? Fresh gas may cure your problems.

Just filled it with fresh 93 but while taking my intercooler couplings off to check for boost leaks I noticed could move the CAS by hand so I picked up a timing light tonight and gonna check it tomorrow

[1988montecarloss]

Don't forget to check the tps voltage open/closed

How would I do that? Can I do it with just a normal multimeter?

[RB25GUY]

How would I do that? Can I do it with just a normal multimeter?

Yeah you can .

[bmxguy08]

How would I do that? Can I do it with just a normal multimeter?

like stated above this is very easy to do there are many videos and threads on this out there.

Set that CAS first off. Also I had this issue my car ran tits for 3 months then it startted sputtering and cutting out under high load. I re-grounded my engine to the chassis and re-grounded my coil packs and it fixed the issue.

Also pull your plugs and check for carbon build up and also check the gap on them.

Wouldn't hurt to put a relay on your fuel pump straight to the battery there are again many videos and threads on how to do this.

[1988montecarloss]

like stated above this is very easy to do there are many videos and threads on this out there.

Set that CAS first off. Also I had this issue my car ran tits for 3 months then it startted sputtering and cutting out under high load. I re-grounded my engine to the chassis and re-grounded my coil packs and it fixed the issue.

Also pull your plugs and check for carbon build up and also check the gap on them.

Wouldn't hurt to put a relay on your fuel pump straight to the battery there are again many videos and threads on how to do this.


Fuel pump has been hardwired with a relay for a couple years now (walbro 255) and plugs are almost new and gapped tight .020"

Also did a boost leak test and found one so gonna try to keep that from leaking today and then putting a timing light on it if I have time

Also is it better to ground the coilpacks to the engine or chassis? I've tried both and haven't noticed any difference

[1988montecarloss]

Ok this is getting annoying, fixed all boost leaks and set timing to 15 degrees (2nd mark) with a timing light and now it runs even worse lol

Which makes me believe it's a fuel issue but the pump sees almost 14 volts and makes 43psi at the rail

[1988montecarloss]

Just checked tps and got 0.44-0.45 closed and 4.04-4.05 open, is this within spec?

[jedi03]

that makes it sound like timing may be a tooth off...I would check it all including each cam personally...I know its a bit of work and would be weird if that happened but sounds like mine did when was that far off...

[1988montecarloss]

that makes it sound like timing may be a tooth off...I would check it all including each cam personally...I know its a bit of work and would be weird if that happened but sounds like mine did when was that far off...

With the CAS turned all the way clockwise it stops misfiring and makes good power at WOT but is still lean at 15:1 and isles erratically after that, thinking maybe the CAS is stabbed in a tooth off

[1988montecarloss]

Have checked ignition timing and checked marks on CAS and everything is timed correctly and lined up, have also ran a fuel pressure gauge and car makes perfect fuel pressure and adds psi as it should and during a pull doesn't drop pressure at all, got my new coils and maf in the mail tonight and installing those tomorrow

[jdm-specs]

Hope you don't me chiming in, but it's a good thing that you check fuel pressure reading while the lean problem is there.

I think you should focus on you lean condition under load first, as it is more likely causing it to break up, seems more likely to be a fuel delivery problem when it's only lean under load, compared to ignition. Do you know if the ECM is storing any fault codes?

Although the MAF seems reasonable to swap out. Maybe a good idea to swap out a set of known good injectors and check the ECM grounds for any rodent damage since the car was sitting for awhile. Since you changed out the fuel filter and verified fuel pressure already.

[tuzzio]

Check your grounds. They make the car do weird shit.

I used to have some bad issues with draw between turning my lights on and my e-fans. Added another engine to chassis ground and a alternator to chassis ground (I had some leftover 4GA wire laying around) and when I wired my fans I used separate relays and 10GA power wire and its EONS better

[1988montecarloss]

Checked all grounds and were all fine, also swapped out MAF and another set of injectors with no change but I did install a set of splitfire coils that made a huge difference, car runs better with them than it ever has even with a larger spark plug gap but the gauge still reads lean, can't hear the car spark knocking and plugs look good after a WOT pull so thinking my lean condition is either a faulty wideband sensor from being run super rich and like crap for so long or has to be recalibrated, do the aem uego need to be recalibrated? If not a new sensor will be my next move

[jedi03]

they can be...aem has a faq page...when mine did that I got new sensor from autozone...had to cut out a portion of the clip I found to be similar...no issues since then!

[nisileighty]

Not sure if this issue has been resolved but here’s my thoughts.

Since it’s an RS-Enthalpy tuned, I’m not sure if you can set the timing to 15* and call it good, as the ignition timing was probably advanced to make more power.

The TPS could also be a big problem, my SR ran like shit when it was bad. There’s plenty of sources online that show how to do this.

Lastly I’d check that you don’t have any fuel leaks, or a loose fuel clamp or something of that sort.


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