Resetting the ECU, is this normal?!

[skillzilla]

I went about resetting my ECU after diagnosing and replacing a bad coilpack and re-timing my motor. I was also throwing a code 34 (Knock Sensor), so I thought maybe resetting it would clear the code anyways.

So I time the motor to 18 degrees, reset the ECU, and take it for a spin. WHOA!!! This thing was bucking like crazy!! I took it easy and it evened out a bit, but still slowly easing onto the throttle in 3rd-5th would bog the motor and it would buck/kick like crazy. I stopped and checked my codes, read 55, so I continue, and noticed it would predominantly do it between 4-5k on the tach.

Is it normal for it to kick that much? I know the ECU advances and retards timing when you reset it, but this was nuts.

Anyways, also tried to figure out a high-idle problem, set the idle per the instructions from SDU, still super high (like 1100), so I cleaned the MAFS, the throttle body, and pulled the AAC and cleaned that.

Still no dice. I know its not my timing because I rechecked that at the cylinder #6 loop AND at cylinder #1, both were the exact same.

LMK if you all have any ideas

[Carl H]

rb20 needs to be timed to 15 at idle.as for the super high idle might need the tps adjusted.

[eh?]

Maybe you misread and it's actually code 43 which is TPS. I had a bad tps and it caused the same symptoms you have.

[skillzilla]

Its not a bad TPS, my Emanage is reading .55V at 0% and 4.xxV at WOT. Code was definately 34, Knock Sensors.

Wasnt throwing any codes as of tonight. Good news is, looks like I fixed my high-idle somewhat

Im about to do a KA-T, this motor has more Gremlins than a 80's movie marathon

[skillzilla]

OK, update time:

I took off my top timing cover and checked my cam gears for the right setting. I also noticed my crank pulley was a hair on the left side of the timing mark when my cam gears were lined up, so I loosened my adjustable cam gears and pulled them both back 2 degrees.

I put the motor back together and rechecked my timing, it seemed to be smoother from the get go, and I let it warm up.

Retimed the motor for 15 degrees btdc, and went for a drive. WOuldnt you know it, same fkin issues. It only happens at >50% throttle, almost like Im running super rich and its bogging the motor. No codes on the ecu either.

Imma reset the ecu, time it again, and replace my fuel filter which Ive had for almost two years in there.

LMK if yall have any ideas. Im stumped.

[Wulfgang]

My first thought is that it is almost certainly the MAF circuit. I know you cleaned it. And I know it worked before. So did mine.

But then one day, out of the blue, it started the bucking thing you described. I took it home, shortened the MAF cable by about a foot (I had waay too much length), and the problem was solved.

The MAF circuit is sensitive, very sensitive. So I would suggest first trying to re-seat the ECU plug and then if that does not work, try using some foil or braided metal cover over the MAF cable.

[skillzilla]

Alright thats an idea, will definately try that tomorrow. I replaced the fuel filter, reset the ecu, retimed it (fo about the 15th time), and no dice. Ill do an update after I try out the MAFS wiring.

[skillzilla]

OK, I unplugged the MAFS and it raced a little bit, replugged it and it almost died, then recovered. I checked my MAFS voltage with my Emanage and it was normal (that is, fluctated between 0 and 5V with air intake, like normal).

So I take it out, do some driving, same issues of course (didnt change anything), came back and I threw a code for my MAFS!!

Finally getting somwhere, helluva job diagnosing the MAFS circuit Wolf

Anyways, how could I test the circuitry? I assume test power, ground, and signal on the MAFS, and the same on the ECU pinouts. Which wires are what on the MAFS, u know? I extended my wires and I dont think I used OEM colors for them, so numbers from left to right would be awesome.

Thanks again

[Wulfgang]

Don't rule out anything else yet... you could've thrown that MAF code when you disconnected the MAF to check it.

Wiring goes like this: There are two shielded wires. The white one is signal ground and goes back to the ECU (pin 4 on MAF). The other one might be silver... or black with a silver stripe, I dunno. Whatever it is, it is the signal wire (pin 2 on MAF).

And then there are two unshielded wires: the black one is ground (pin 3 on MAF). The other one, black with white stripe, is the battery voltage (pin 5 on MAF).

So it goes like this:Pin 1: no connectionPin 2: shielded, signal (silver stripe?)Pin 3: unshielded, ground (black)Pin 4: shielded, signal ground (white)Pin 5: unshielded, battery (black/white stripe)

If noise is the problem, it will be easier to fix than to diagnose. If you can, disconnect your e-manage and re-do your wiring, making sure to use shielded cable for the 2 signal wires (but NOT for the 2 power wires).

[skillzilla]

Edit: Everything seems to be in working in order, took a bit to get the signal voltage at the ECU but that was multimeter user error

SO is there a chance that all 4 wires are showing no problems but I have interference or noise, or a bad MAFS? Seems that if all the wiring is showing green then something else is the issue.

BTW, on a whim I checked my knock sensor voltage at the ECU, both showed ground but not complete ground (needle didnt shoot off the dial like a normal ground). Is this normal?
Modified by skillzilla at 5:51 PM 10/28/2005

[skillzilla]

!!!!!FIXED!!!!!

Reset the ECU, and while I was waiting I decided to check my plugs and regap them to .7 (off a tip from SAU). They were all gapped to 1mm, which surprised me, so I regapped them, put it all back together, and ran like a bat outta hell!

No error codes, and the sputter is completely gone. Im going to give it a few days and make sure, but looks like that was the problem. I think it started acting up lately becuase we (in GA) had a huge cold front come in this week, and the temps dropped from 50-70's to 30-50's.

[Wulfgang]

I don't want to sound like a space cadet here, but....

Smaller spark plug gaps likely produce less electrical noise than larger ones. And no, even if your multimeter shows all good connections on the MAF, you cannot rule out electrical interference as a problem.

The MAF circuit is high impedance, which means that even a small amount of noise will be "heard" on the line if it gets into the circuit. This is a characteristic of the circuit and has nothing to do with the quality of the wiring (but it does depend on the quality of the shielding).

So it is possible that gapping your plugs decreased the electrical noise under your hood enough to let your MAF send a good signal. "Stuttering" from misfires is usually a symptom of bad plugs. "Bucking" is something quite a bit different and is usually (in my experience) caused by screwed up control systems.

But then again, your MAF may have nothing at all to do with your problem. Glad to hear you got it fixed tho. Whatever works to keep it on the road, right?

[gawdzilla]

bringing up this old thread... i have the exact same problem. my car bucks back and forth occassionally, and it is definitely one of the MAFs (rb26 here).

Looking at my pfc while my car is surging, the voltages across the rear MAF bounce up and down erratically, sometimes even going to 0 completely while at a stop. I switched rear and front MAF plugs only, and the problem moved to with the connector. I ruled this as a wiring problem.

Disconnected my harness and took it apart. I'm using all factory wires and I extended them with "proper" aluminum foil shielding. Everything seems to be fine. I even got a replacement connector hoping it was a connector issue.

The only thing I can think of is my rear MAF wiring is about 12-15" longer than my front MAF wiring. I will try to shorten it a bit and see if it helps. any suggestions guys?? thanks

[Wulfgang]

Did shortening the cable fix the problem? If not, make sure your foil shielding is grounded and then check the ECU connector also.

[matt_calgary]

I have something similar as well. Idle is really high, seems to be getting higher by the mm per day. As of now, its usually 1500RPM. RPM is stable but high. I have stereo wires(about #8AWG or #6AWG) running on either side of my car(like this when I bought it). Could this be creating noise on the MAFS circuit since the ECU is very close to these wires? I still have to check if I have a vaccuum leak as well. Even when I come to a light in second gear and have it around 2000RPM, put it in neutral it slowly drops to 1500. However, I don't even touch the idle screw and sometimes it'll idle at 1000. Its most bizarre but its been fairly consistent with the higher idle then not.

[gawdzilla]

problem not fixed... the mafs still bounce around randomly when i'm trying to hold a constant throttle. this is only happening on ONE MAF and it is pissing me off...

i'm gonna go find some matching gauge shielded wire tomorrow and redo the whole thing. maybe somewhere along the wire is frayed??? i'm out of ideas. cant be the ECU b/c i have 2 pfc's in my posession right now... same result. siwtched the MAF connectors, and the problem moves... so it must be the wiring. maybe it is the ECU connector itself?? but why would it just bounce around?

EDIT: ok i'm retarded.. the logic i was using to figure out if it was a maf problem or a connector problem was completely reversed guess thats what happens when your transmission tunnel isnt sealed and you're dying from exhaust fumes... i'm gettig a new maf. my guess is this will fix it
Modified by gawdzilla at 8:44 AM 12/1/2005

[rb20detsilvia]

ok seems like i have the same problem what does he mean when he says the sheild needs to be grounded

[Darius]

Where does one find "shielded wire"? I went to O'Reilly and Radio Shack and O'Reilly didn't have anything and the Radio Shack guy looked at me like I was retarded. Maybe it was him...I dunno.

Also, is there any special technique to splicing shileded wires together (besides not overlengthening as Wulfgang has pointed out)?

[Wulfgang]

I do not know where to buy good shielded wire locally except for microphone cable, which should be shielded. I despise RadioShack, tho. Going in there is like going to a used car dealer. If you need a microphone cable, they might try to sell you an ethernet cable, not knowing the difference. And then they'll always, ALWAYS ask you if you need batteries with that microphone/ethernet cable because they have such and such special going on with batteries. If you do go that route, be sure to get stereo microphone cable because you'll need the extra conductor.

So anyway. I took every last bit of shielded cable off of my KA before junking it, so I have some spare stuff with automotive quality. You could certainly order good stuff from Digikey, but you might have to order a whole spool. Or you could go to the junkyard.

Splice shielded wire just like you would any other wire, but make sure you also splice the foil or braid shielding. To do this, pull the foil or braid back away from the wires and twist it up to make a spliceable wire. Do the same to the shield on the other cable and then solder the two twisted shields together just like you would with any other wire. The shield does not have to cover the splice, but keep the unshielded length to a minimum.
Modified by Wulfgang at 5:11 PM 3/20/2006

[Darius]

I am assuming that you should you insulate the shielding splice "wire" from the signal wire so it doesn't ground the signal?

[Wulfgang]

Yes, insulate everything.