SR sputtering/bogging/misfiring

[SHIFT_*grind*]

I know there are 1,000,000 threads on sputtering SRs, but I'm going to try and be as descriptive as I can and relate all the events that have occurred since the last time the car was running well.

My former setup
Kouki S13 blacktop - Walbro 255 - GTiR T28, HKS actuator @ 10psi - Taka lines
3" turboback - FMIC, 3" cold piping, 2-->2.5" hot piping - Recirculated DSM BOV
Stock manifold, FPR, injectors, ECU, MAF

Car ran fine. I didn't like the power delivery of the GTiR turbo, so:

Installed: S14 T28 - Espelir exhaust manifold - Different dump pipe
Slightly different hot piping - New BKR7E copper in place of old BKR7 iridiums

Started the car up. It smoked from the turbo a little at first, but I didn't worry about it since the turbo's mint and it was the first startup. Ran OK, with some hesitation throughout the rev range, but boosted hard. Nasty sound, like a chainsaw, when boosting under load. Also, at one point during the test drive, I stepped on it and the boost gauge swung over to ~15 psi :eek3: before I yanked my foot off the gas and took it easy the rest of the way home.

The sound made me think of a bad exhaust leak, near the turbo, so:

Installed: Better fitting dump pipe, and adjusted the WGA down so I don't blow shit up

Save for the lower boost, absolutely no change. Also, hesitation seems maybe a little more pronounced; car sputters and idles really low for a few seconds on startup, then stabilizes at around ~850RPM, but I can still hear it missing. I eventually realize that the multi-layer manifold gasket may be keeping the manifold from sealing flat against the head (because the flange is 1-piece, and the gasket has little rivet things between the runners).

Installed: Stock manifold, and reset the ECU

Noise is gone. Car still sputters and hesitates, and starts rough. Boosts fine, but the power just isn't there.

Today I pulled the plugs. The two nearest the firewall look fine. The two nearest the radiator were as white as can be. The older iridium plugs, before I put the new turbo/manifold on, weren't like this.


What's up? The apparent lean condition in 2 cylinders makes me think injectors, but I feel like it would be more likely for it to be a result of something that I changed. I thought maybe timing, which I haven't checked yet, but it was fine before I did any of this and I haven't touched the CAS, except to unplug it to crank the car to prime the turbo with oil. Also, bad timing should cause excessive heat in all the cylinders, not just 2.

I'm going to check the timing, the coil packs, and maybe the compression next; I wanted to see if anything's jumping out at you guys as being the most likely culprit, given all of the above info.

[SHIFT_*grind*]

Anyone have any ideas?

[slider2828]

You can check your injectors by looking at the FSM. Testing the ohms on the each injector based on specs from the FSM will tell you what is up with the injectors.... Try the KNOWN problems first before starting to speculate.....

[SHIFT_*grind*]

OK, I'll pick up a multimeter and check the injectors first. In the meantime, not to speculate too much but......would it be a good idea to do a compresion/leakdown test as well? I'm an alarmist and can't help but worry that the sputtering/loss of power means I might have seriously damaged something when it spiked to 15 psi :(

[slider2828]

Unless you are spewing massive amounts of smoke out of the tail pipe, its not so bad yet. Check the injectors and go from there. I would do a leak down test if you have the equipment like a compressor and stuff, but otherwise just start with the injectors first and go from there...

If you post and don't see me reply, just PM. I kinda stopped looking at Tech Area cause the questions are the same usually and the split up the sections, so its retarded to check all 3 sections like S Chassis and bla bla bla

[SHIFT_*grind*]

OK. Checked the injectors, resistance is dead-on for all 4 at 11 ohms (FSM specifies 10-14). I moved on to the TPS, and as best I can tell......it's way out of spec. Resistance between the terminals should be 0.7k with the throttle closed, and 5k with it fully open. It was 1k with the throttle closed, and ~10k fully open (twice what it should be). I adjusted it a couple of times and was able to get it to 0.7k closed, but it still went up to ~10k when I opened the throttle.

So, the FSM tells me I need to replace the sensor, which is exactly what I'm going to do. Could that explain what's been going on with my car?:

-No power; stumbles on acceleration, kind of jerking forward; boosts fine, but just doesn't accelerate, it takes me forever to get to 60mph because I can only give it a little throttle without it stumbling
-Idles extremely low on initial startup, like 200rpm, just exactly enough so that it doesn't stall out. Idles fine once it warms up, right around ~850rpm, I just can't give it much gas under load before it stumbles
-It's been getting progressively worse

Also, I checked the resistance on my coil packs. Most of them are relatively close to the 1 ohm factory spec (like 0.7-0.8), but the #2 seems really spotty. It was really hard to get a clear reading, it kept jumping all over the place. The #1 coil pack was also a little loose.

[slider2828]

There you go, all those things really indicate whats been happening to your car. The TPS Sensor really tells the ecu how much fuel for air it needs to compensate and tells the car what throttle position you are at. Well its all speculation, but incorrect readings for TPS will tell the ECU wrong information and hence wrong fuel maps, etc etc. Obviously if it can't tell what your throttle is, then its going to anticipate the wrong fuel amount to dump in. In realistic specs, close is around .7 and open about 4.7. You are like completely wacking the computer and it simply doesn't know what to do.... Replace it. Also if everything doubles, your 1/2 throttle tells the computer that it is at full throttle and just right away dumps gas or does something weird and of course you stumble. So you have to think of it that way... Replace away sir....

In terms of coils, if it is close its ok, but after you replace the TPS and things run right, keep in check the spark splugs and see if you notice any coloration differentiation. So like all the spark plugs should roughly have the same color. If not then you probably more likely have to replace the coil packs...

[SHIFT_*grind*]

Yeah, that's how I was rationalizing it to myself; I wanted to get a 2nd opinion. :) Thanks!

[slider2828]

Get that bish fixed up.... Hopefully it all works out for you. Good Luck

[SHIFT_*grind*]

OK. I purchased a supposedly working TPS from a Zilvia member. I put it on the car today, and there's no change. The resistance readings are the same: ~10k ohms at full throttle, twice what it should be. I think "well shit, I got sold a bad TPS," but the member, who's parting out their car, says the car ran fine. The car has cams, GT2871R, 740cc injectors...and a PowerFC.

I don't know if it's a D-Jetro or L-Jetro (MAP or MAF-based), but would a PowerFC even take readings from the TPS? It seems possible to me that, since it replaces the stock ECU and is standalone, it may not even need the TPS...especially if it's MAP-based. So this person's car could have a bad TPS and be running great anyway.

Can anyone provide input?

[SHIFT_*grind*]

?????????????????????

[SoSideways]

Did you run a diagnostic on your ECU to see if you're pulling any codes?

[SHIFT_*grind*]

Actually no, haven't checked the ECU codes. I'll give that a shot. A bad TPS would throw a code?

[SoSideways]

Actually no, haven't checked the ECU codes. I'll give that a shot. A bad TPS would throw a code?

A bad TPS or wiring should throw a code.

Along with anything else.

If your ECU doesn't throw any codes, then it could be a mechanical problem.

[rotation3x]

I have the same exact problem, I was running the same plugs and swapped them out with the bkr7es and my a/f read really rich at idle. so I swapped plugs and It didn't change anything. I took it back to my tuner and it was sputtering on hte dyno after he did 2 pulls in a row the 3rd time it sputtered bad at 5k rpm. I looked under my hood and noticed coolant that had been seeping out of my radiator cap. I think I have a head gasket leak going into my combustion chamber on cyl. 3 since the tip is greenish colored. My 1 and 2 cyl. plugs where both white like you said.

I am running a power fc and am wondering since this is my 3rd headgasket in 4 months if it has something to do with my ignition timing causing detination leading to blown head gasket.

[SHIFT_*grind*]

I checked the ECU and got code 34: Detonation/knock sensor. Could that cause all of my problems (almost no acceleration; really bad idle on startup)? Could the knock sensor be so far gone that it would pull timing THAT much?

Someone suggested in another thread that faulty ignition, resulting in a miss, could cause the ECU to throw a knock sensor code...does that make any sense?

[SoSideways]

I checked the ECU and got code 34: Detonation/knock sensor. Could that cause all of my problems (almost no acceleration; really bad idle on startup)? Could the knock sensor be so far gone that it would pull timing THAT much?

Someone suggested in another thread that faulty ignition, resulting in a miss, could cause the ECU to throw a knock sensor code...does that make any sense?

The ECU can pull up to 4 degrees of timing and dump a ton of fuel on the Z32, and since their ECUs are quite similar, I could only imagine the SR ECU will do about the same thing.

How much timing does it pull? I don't know, but at least 4 degrees.

[slider2828]

Seriously, I usually figure ECU codes isn't an end all. It just says something is messed up. Replace the Knock sensor... check the ECU codes. If your TPS is known good then try the knock sensor.... Then check codes... At least you have some idea, when I fried my ecu I had no way to check except the ECU had 0 power while everything was being powered up.

[SoSideways]

Seriously, I usually figure ECU codes isn't an end all. It just says something is messed up. Replace the Knock sensor... check the ECU codes. If your TPS is known good then try the knock sensor.... Then check codes... At least you have some idea, when I fried my ecu I had no way to check except the ECU had 0 power while everything was being powered up.

No the ECU codes aren't an end all to diagnostics on a car, but it gives you an idea of where to look, seeing as there are hundreds of symptoms that can be traced back to a couple of sensors or mechanical devices.

[slider2828]

lol yah.... hahaha Hey

Think about the ignitor too. Maybe you hae a bad ignitor and check that too.

[SHIFT_*grind*]

Just to update: the MAF was bad. I don't know why that would trigger a knock sensor code, but whatever. I swapped in a working MAF and, damn......I never knew the car was supposed to run like this. :eek3:

[slider2828]

Great! So happy for you....

[SHIFT_*grind*]

Thanks for the help man. I'm pretty happy myself, this thing hauls ass :) It did, anyway, and then my alternator went out later the same day...... :mad: Oh well, at least I know what the problem is this time and it's bolted right there to the front of the engine...

[jorgezee1]

thanks for the update...

[rb25_s13*CHUKI]

Just get a rotary man

[SHIFT_*grind*]

I might actually have fewer problems with one of those.

[slider2828]

Until you get to 60k miles and you gotta rebuild lol...

[landins13]

the maf being bad would trigger a knock sensor code because you are running lean and creating detonation, which in turn will trigger the knock sensor.

in my personal opinion i would rather be running rich as hell then lean, every day of the week, running lean creates an excess of oxygen in the cylinder, and when the fuel burns off there is too much air causing little bubble or pockets that explode and can ding and dent your pistons, or even cause your motor to blow up completelly depending on how bad the conditions are.

[slider2828]

Hmm interesting.... Well I don't think the tried to "run" the motor, just diag, but that is a great explanation... But would it run lean?