AFR's gone wild - IHATETUNING -

SON240sx Automotive
1

cross posted - WTF??!?!

at the tail end of a real sharp SR20 build: tail end because either i smash it with a hammer into pieces or tail end because it finally works.

we have an Innovate LM-1 wideband hooked up to the exhuast. before the motor blew i was able to run proper AFR’s and control with SAFC with ease.

nothing has changed except the motor, full rebuild, all forged internals etc.etc. but the thing just wont behave.

at first it wouldnt hold idle and would just die and flood out. we got it to hold idle now but it is sooooo random.

case in point.

start the car, wont start… unplug the injectors to burn off fuel in the chambers, burning the fuel, plug back injectors… car starts… runs 10 - 11 AFR’s = bad.

change the spark plugs and regap, plugs were only 3 days old with maybe 10km’s on them and a half hour of total run time. may or may not be salvagable and dont care.

start car back up. running proper AFR’s, go for drive. throttle is internittant. reads 0 on SAFC until you give it a good tap and go over 15 -20 %. throttle signal cuts out and back in on low throttle cruising.

bring back to the shop, fuck with the TPS / SAFC wiring etc. iono how chris fixed it but he did. but… car is now running 10 AFR’s again and flooding still.

pull injectors, burn off the fuel, car starts, running 10 AFR’s… trying to figure out why… all of a sudden leans out to 18 AFR’s… then 19 AFR’s, engine starts hunting… up and down up and down… leans out to 20 AFR… tap throttle… dies

try to start, floods. change 550cc deatschwerks injectors with brand new 650CC’s. visible wear on seals, they were likely leaking.

start car at -10% correction on SAFC (Enthalpy ECU for 550’s btw) starts and runs nice high 14 low 16 AFR’s - loving it.

car starts to hunt again… up to 18AFR 19 AFR 20 AFR tap throttle = dies

car floods on new injectors - pull and burn fuel and start again

etc. etc. etc. been going on none stop for 2 weeks.

at at least two points this evening we made changes and had the car idling properly between 850 - 1000 (cams = set idle a bit higher and to prevent dieing on decel with current imperfect tune). at these times the AFR’s were nice and controllable with the SAFC.

when the car riches to 10 AFR the SAFC cannot lean it out back to 15 AFR even at -50%. however, when it leans to 18 - 20 AFR i can bring it back with the SAFC…

when changes are made, ie. new injectors or new plugs it works the first time and then floods and goes back to the same problems…

its 3am i have to work in the morning and have exec meeting at 10:30 = ghey ghey ghey

car must run for proper break in so i can beat the fukking shit out of it on the weekend.

go…

2

we have gone through this same cycle of events literally 20 times or more… changing things out with brand new parts (injectors / plugs / FPR etc.) always starts right up after the change then goes back to all the same problems

btw… put on freddy manifold if that makes a difference.

3

It really sounds MAF related.

  • Clean it / Use SAFC to ensure MAF is reading correct voltage
  • Make sure the plug is firmly connected. Make sure it is grounded well. Your wiring could very well have been disturbed
  • Swap MAF out for one known to be working
  • Check SAFC setup. Worse case scenario uninstall the SAFC just to take it out of the equation
  • Plug a stock SR ECU in there just to see how it idles
4

My car wouldn’t stop stalling until adding 40% more fuel at 1000 rpm on the safc after installing my freddy manifold.

5

is your fuel pressure ok?

i rememeber pavel had a problem where his car was running so rich at idle it was blowing black smoke and he had to keep pulling the injectors since it would stall and i think it was his maf wiring or maf its self. he had it fixed in like 2 seconds it was wild.

6

we have eliminated the SAFC and even tried a second SAFC

swapped out FPR for another FPR that was laying around, same thing happened, the AFR’s got very slightly better for the first 4 minutes, then back to gheyness.

mafs i havent looked at, assumed it was fine, me thinks Danny that i should borrow yours…lol…

if it were mafs then would it not have to be wiring? if it were a physical problem with the MAFS it would be constant no?

7

it depends, sometimes if your maf wiring is shorting out it can send a bad signal to the ecu, but i doubt its that its probobally just a cooked maf maybe you dropped it or got dirt in it when you swaped the motors.

that would also explain why your safc is doing nothing to help

8

but the safc does do something when the AFR’s are normal.

yeah i guess that sorta does make sense, if the MAFS is intermittant, like the faggot throttle signal… it does bog at 10 afr like mafs being ghey…

Dan, get your mafs down here… lemme try your PFC too… friend

9

Double check your wiring Bing, unlikely but you could have knicked something possibly MAF wiring re and re-ing your motor hence causing an intermitent miss.

10

Binzors - is Chris at the shop tomorrow (Wednesday)

I am heading to Welland for an AM meeting. I can drop off my Z32 MAF and PowerFC for testing.

That being said, Chris is coming to my place that evening so he needs to test ASAP and bring that stuff back to me on Wedensday evening.

Let me know if this will work.

PS - YOU BREAK IT - YOU BUY IT

11

yeah i am sure chris will be there, if not, i can do the mafs in 20 minutes.

PFC i dont want to touch at all…lol

i do not know where my extra block and crank are either dan, you’ll have to ask chris about that. It would be best to get that going sooner rather than later.

12

Having talked with Bing about this here is my take on it all.

First off it sounds install related like a bad connection or something that is intermittent, not something that has just gone bad… However, I never eliminate possibilities based on what I think, I try to prove my theory right by eliminating the easy stuff. Start big and narrow it down.

So off the top of my head here is what I would do. I know a bunch of this has been done but maybe something got missed. In no way is this a direct jab at Bing/Chris, shit happens and sometimes you can get lead down a complex path when it is really something simple.

Compression, fuel and spark. Simple enough.

  1. Compression, check it, make sure something isn’t fubar, it can happen. If you are so sure there is nothing wrong then 5 min to confirm what you think will only help you narrow it down.

  2. Fuel. This gets pretty damn complex to get right but you either have the right amount at the right time or you don’t. Only so many things control it, no need to check the diff fluid if you think there isn’t enough fuel…

You NEED a fuel pressure gauge on it, period. If it is wandering up and down from a bad pump, pump wiring, plugged filter, messed FPR you will find out in no time. Literally 5 min worth of work. The gauge doesn’t even have to be accurate, just hook it up to a good running engine and note the value. In this case you aren’t looking for a 2 psi difference so much as a varying pressure or WAAAAAY high/low. Something significant.

If you can confirm there is the right amount of pressure, all the time, you need to make sure the injectors are all working. It sounds like they are opening so that is good.

Right time? Too long? Since they are new I wouldn’t spend too much time checking to make sure they are good, especially since you changed them for a completely different injector but it is something to think about. You already did the quickest thing by changing them and the problem persists so I would conclude the injectors themselves aren’t the problem but still possibly how they are being triggered. This includes MAF telling how much air it is getting etc… I will come back to items that are in two categories after spark.

  1. Spark. You changed plugs, did you check spark with the plugs out but coilpacks on them? ie crank it over? If you have a spare CAS you can plug it in (leave the other CAS hooked up to keep the timing right) and turn it by hand and watch the spark. The injectors will also fire if you ever want to confirm they are all working. Good way to double check your assumptions.

As Bing told me, I understand the CAS is aligned as per the timing mark/dots on the CAS method. You may want to double check that since it doesn’t take too long. It would have to be way off/changing to get the symptoms you have but it IS possible to have a loose “wheel” in the CAS which COULD do that I suppose… Confirm the cams are timed properly while you have the valve cover off. Why? Why not…

General BS:

To me it sounds very suspect that it will start up just fine with new plugs each time. Check all the wiring related to the coilpacks and CAS. Make sure you have full voltage when running AND with key on only. I forget what it all should be but the FSM has good tests for each sensor. All you have to do is extend what they say through wires to the ECU and check it there, if that makes sense. There could be a bad connection at one of those plugs that is intermittent. The only way to be sure is with a meter. The ECU inputs are pretty straight forward signals. Check them at the source AND the ECU, maybe something got damaged as someone suggested and it is grounding out somewhere.

To check the MAF you should see roughly 500 milivolts at the ECU, maybe 300. I forget off the top of my head (I will check on my PFC later if need be) but it shouldn’t be all over the place nor close to 1 Volt at idle. If it jumps all over the place back track the ground, source voltage, etc. As I told Bing if I had to guess I would say the chances of the MAF/CAS/TPS going bad are minimal but change them if you have known good ones. Sometimes the time it takes to check something is far greater than just swapping the part to begin with. Once you have switched everything you can dig in more with the meter. Don’t assume since you have changed the MAF that it isn’t the problem, check the signals to/from it. Changing a device only confirms the device itself isn’t the problem (assuming the one you put in is know to be good).

I can’t stress NOT jumping around changing shit. You will need to pick a plan and stick to it until you have exhausted all the related paths. If you think it is spark check it ALL. Confirm the stupidest things you would think “not possible”.

I say it is something stupid simple, bad connection or something. Check grounds WITH A METER. Battery voltage is where it should be at the starter, etc. All that shit takes no time to check but forever to dance around when you assume it is ok.

Yes, this is a pretty terrible post organisation wise… I am just trying to throw what I told Bing out for others to see off the top of my head. I therefore reserve the right to edit it when I see that what I am trying to convey isn’t clear to the reader… :oops:

13

I’m a noob and I’m running Power FC. :dunno:

Why is 11AFR bad when you start it?

On cold mine starts around 12ish and then after warmed up at idle it sits
around high-13/low-14s

WOT I have about 11.7

Part throttle, little load, in town cruising I’m at about 15-17.

This is running the base Enthalpy maf that I had to slightly lean out at
mid-range.

SO anyways, this is all on the SAFC or the Power FC?

14

word, thanks for the post evan.

Dan… bring your split fires too…lol

i’ll check some of the stuff you mentioned late this evening.

15

10 AFR = very very rich, especially at idle, whats worse is that the car bogs and wont rev when this happens.

likely a spark or air thing. since it isnt the plugs i’ll have to check the coilpacks. i had one fail on me a week or so ago and i replaced it with another one. i’ll try that again

16

to much monster green for you…YOU’RE CUT OFF!!

17

that shit had me up until 3am…

honestly, who else can remove the whole turbo-side of an SR20, manually prime that shit up and reinstall in under 3 hours?

pretty sure its just me and you

then again, when its your 6th time in 6 months i guess we better be getting good at it.

18

Evan,

i gave some thought to the coil pack harness maybe grouding out.

if that were the case we should lose the cylinders completely. when the car starts up and it running those 10 AFR’s it is still idling on all 4 cylinders.

there has to be some spark there.

with teh MAFS, i have experienced in the past when the MAFS is shorting out or the plug is loose. it feels like an intercooler leak in that you can idle alright and even move the car around but once you get above like 2000rpm the engine just bogs.

the SAFC is getting air flow readings all the time, so the connection from the mafs to safc to ecu should be good.

19

also,

i jsut spke with chris,

he was at the shop and had the car idling fine, then he closed the hood and it all went back to the shit AFR’s… WTF?

20

I think my MAF went last week.

I went to drive off in the morning, and the car just sputtered.

I also had noticed really rich AFRs when driving around (a lot richer then noramal).

My power was also messed up (as if I had no power at all).

One day as I was to drive off it happened and I openened hood and last
thing I wiggled was the MAF before trying again and then it drove fine, but
the car was still shitty feeling.

I just said F this and put the PFC in for good, crossed my fingers and
hoped for the best. So far so good. :dunno:

I would point at MAF and then maybe coilpacks.