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Discussion Starter #1
So I’m having issues where my plugs foul after about 30 miles of driving, and cause the car to break up in the low to mid rpm range and getting less than stellar mpg. I believe I’m running too rich because of the major carbon build up on the plugs. Its a fresh rebuilt y8 with with less than 1500 miles. It has skunk2 intake and tb, comp cams QuickTyme 105100 stage 1 camshaft, 4-2-1 headers with cat delete, stock mid section with a axel back muffler. Everything else is stock. Now I’m untuned for now (saving up for a s300 and tune session, they ain’t cheap lol). But my major question is, will putting a 1 step hotter plug keep me from fouling plugs until I can get it tuned? And if so what recommendations would anyone have? Any help will be greatly appreciated and thanks in advance!
 

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Discussion Starter #2
Also I’m running ngk vpower zfr5f-11 and a .44 gap. (The stock plug and gap for this engine) and it’s throwing a cel code for catalytic deficiency (cat delete) and iacv (high idle, not surging).
 

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The two on the right seem OK still, the two left are just a bit more sooty but otherwise don't look terrible. The 3rd from the right is the most sooty, are you sure you have good combustion chamber sealing? Perform a compression test just for shits and giggles to make sure it's healthy? Did you adjust the valves to spec after installing the cam? Timing mechanical and ignition set correctly? Is the rest of your ignition system OK? Wires/cap/rotor? If spark is weak at the plugs from the get go, then you will have issues regardless. Usually mechanical air flow mod enhancements to stock engines and ECUs move the AFR's lean because they provide more airflow/higher VE potential, coupled with stock base fuel injection rates? I would say double and triple check mechanical before assuming it is rich causing the sooty plugs. Maybe an injector is malfunctioning? Do you have a wideband to check real time AFRs?

Obd1 or obd2? The way you say you have a catalyst efficiency fault, I'm guessing OBD2 and it's a P0420. If you have no cat anyways, just unplug the upstream O2 sensor to force the ECU to stay in open loop. Aftermarket camshafts do not play well with stock ECUs in closed loop.

Before forcing open loop, make sure your ECT readings match your thermostat settings after idling 10-15 mins (approx. 185-195 degrees). If ECT is reporting things are too cold to the ECU (like its saying ECT is 60 degrees but your upper rad hose is 9 bajillion degrees), it will be adding too much fuel for too long a period of time to compensate for a false cold condition which will contribute to a rich running condition. ECT is a critical input in open and closed loop, closed may not actually get reached if ECT is too cold which can also cause richer than normal running conditions in and of itself.

I might tighten the gap up to maybe half the .044, maybe .025 and see what happens? The 5F's should be fine, you should not need to go hotter realistically on a relatively stock engine in moderate climate with just airflow mods. Unless you live in the arctic.... do you live in the arctic?
 

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Discussion Starter #4
Did a compression test the other day, all 4 holes tested in the 180’s. Valve lash is perfect. Mechanical timing is spot on but I’ll recheck the ignition timing just to be sure. Cap, rotor and wires are all brand new. Pretty sure the injectors are good. I tested them during the rebuild and they all checked out. A wide band is going to be one of my next purchases. That’ll definitly tell me if I’m rich or lean. And I agree that with my mods it should be leaner, but usually leaner burning will turn plugs white if I remember correctly. Ect’s seem normal. Gauge reads just below the halfway mark, not sure what temp exactly because it doesn’t have the degrees labeled, and a infrared gauge shows temps between 180-190 at the hose. Thanks for the advice. I’ll double check my ignition timing, even though I’ve checked it a dozen times already. Lol. I’ll try tightening the gap on the plugs and unplugging the o2 sensor if the gap doesn’t correct it. One question though, when I do get a wide band, could I install the sensor in the o2 bung on my test pipe and will it read correctly or does it have to be installed in the upstream position?
 

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What wideband setup are you gonna go with?

Technically without a cat, you are free to define your own upstream and downstream locations, as the one thing in the exhaust where those terms are most widely used to determine a fore and aft position in relation to flow has been removed :)

If you have no cat, placing the wideband anywhere will technically work but you want it approximately 24" away from the exhaust ports at the head. The distance is not because of high temps, it's more to allow the exhaust pulses and turbulence to smooth out and merge before reaching the sensor. This will provide the most accurate averaged exhaust gas sampling position for the sensor to be in, as well as providing decent exhaust temps around the sensor for best overall life. Just make sure to position the bung according to most wideband instructions, usually positioned parallel with the ground then about 5-10 degrees angled up.

I would go with the bung on the test pipe, cap the one near or around the header or collector.

Btw, ECT input for the engine ECU is a different sensor than the gauge. The gauge ECT sensor is a single male bullet terminal sensor under the dist, and the ECU ECT sensor is a 2 pin/wire sensor still under the dist but closest to the front of the cylinder head nearest the water outlet for the upper rad hose. The gauge can read good, but the ECU sensor can be off. It's rare, but these thermistors can deteriorate and get lazy/fail over time.

If your still OBD2, you can go to autozone/advance/oreilly's and get them to plug up with their basic handheld scanners and read global OBD2 engine coolant temp. If the parameter is near or at the thermostat operating temp, your sensor is good while hot and you don't need to worry about that. Then go ahead and unplug the upstream and see what happens.

Just throwing this out there, you don't happen to have an aftermarket fuel pressure regulator used within your setup do you? If you do and it's from ebay and only cost like 30 bucks, those regulators are notorious for causing more issues than helping. Those cheap regulator valve's can intermittently stick, and the pressure gauge that comes with them sometimes is 5-7 PSI off a real calibrated gauge. Base fuel pressure could be too high if you really believe it's running rich?
 

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Awesome thanks for the info!

Was thinking about picking up an aem wideband off of Amazon. Figured that would give me the best results. Ok cool so I’ll just remove the o2 sensor from the test pipe and place it there. Any advice how to keep that pesky catalytic deficiency code away? I know they make simulators and such but I’ve heard they don’t work worth a shit. Lol

Yeah I’m still obd2 and I have my own scanner so I’ll check the ect’s when I get off work tomorrow.

And no, my pressure regulator is stock. I’ll spend the money and get a good aem one in the future when I finally decided to go turbo. I don’t like cheap parts because I’m a firm believer in “you get what you pay for.”

Thanks again for the info! I really appreciate it! Hopefully I can figure this out fairly quickly.
 

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Haha, the ol' P0420. If your car still has the stock D16Y8 ECU, sensors and controls, you should be able to get away with doing the "spark plug non-fouler" trick with the rear/downstream O2 sensor. Search this up on Google for a step-by-step, it's pretty straightforward. Search "spark plug non-fouler p0420". The approach basically uses a spark plug non-fouler adapter to take the rear sensor out of the exhaust stream a bit to provide a flatter overall signal to the ECU emulating a catalytic converter that appears to be working as it should.

A bit of info from my experiences with this trick, and a little background on how it all works:

On your engine, both up and downstream sensors should be typical 0-1V narrowband zirconia sensors. The upstream (pre-catalyst) sensor will fluctuate high and low between 0 and 1 Volt when the ECU is in closed loop, as the ECU continually modifies fuel trim to maintain an average of a .500mV reading from the sensor, which usually equates to around 14.7:1 AFR on normal pump gas. The downstream (post-catalyst) sensor's job is only there to monitor for proper catalyst operation.

Oxygen sensors do exactly what their name suggests, they measure concentration of oxygen in the exhaust gas stream. When a catalytic converter is working normally, it will actually hold and retain oxygen to be used as part of the catalytic conversion process. It will steadily release the retained oxygen as a result. Think of the catalytic converter as an "oxygen capacitor" in this sense, the exhaust gas coming in contains fluctuating amounts of oxygen. The catalytic converter holds the available oxygen for its use, then releases what it didn't use smooth and evenly. The resulting reading from the downstream oxygen sensor is a flat line signal that does NOT fluctuate, indicating that the exhaust oxygen content is also not fluctuating and actually being retained by the functioning catalyst.

The ECU is programmed with enough smarts to know that a steady 0 or 1V signal is an error, and will throw P0420 again if it sees this. It needs to be a steady signal within the 0-1V range, but still every so often move just a bit at a slow and steady rate. Placing the non-fouler around the rear O2 sensor provides this kind of environment to generate the required signal. It pulls the sensor out to maintain a steady signal, but is still exposed just enough through the little hole that it still gets a small amount of change over time.

This trick usually does NOT work if your car comes with factory wideband upstream sensors. The ECU logic surrounding catalyst operation on these cars is MUCH more active and robust. Those ECUs perform active catalyst performance testing, and doing the non-fouler trick on these cars does not allow the correct feedback that the ECU was expecting during an actual test. There is no good way of knowing if the ECU on these cars is actually doing a cat test at any given time.

Lucky for you, the D16Y8 is only regular narrowband sensors all around, so you should be good. Since you're in Florida, the land of no vehicle emissions laws, once you go OBD1 with the S300, then you won't have to worry about this causing a CEL anymore anyways :)
 

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Yeah I’ve read up on that trick with the plug non foulers. But I’m hoping to go obd1 within the next few months so I’ll probably forgo doing it. I can live with that damn 0420 code for now.

That is the nice thing about Florida. Shit if they ever decided to enforce emissions testing down here none, of my vehicles would pass. I’ve ripped the cats off or gutted them on every vehicle in my yard lmao.

So I just checked my ECT’s, the ECU is reading within a few degrees of what my handler infrared reader is showing so that’s not my problem. I also checked my ignition timing again and it’s spot on.

I’ll let it ride for a a few days and see how it goes with the plug gap being tighter. If no improvement I’ll pull the upstream o2 sensor to throw it into open loop. Meanwhile I’m gonna order a a/f gauge and wait for that to come in.

Thanks again man!
 

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So after driving about 40 miles today I didn’t notice any breaking up except while I had the a/c on. With it off it wasn’t doing it, but it’s still pretty sluggish down low. And I smelled fuel when I came to a stop a couple times so I’m pretty sure I’m running rich. I also ordered a wideband sensor to be 100% with no guessing. That’ll be here in about a week.

Gonna pull the plugs tomorrow and check them out.

I actually have 2 sets of plugs and have been alternating them about every 50 miles in the last few weeks since I’ve been having this problem. I cleaned and gapped the set I put in today and kept the set I pulled out with out cleaning them. Both sets will have roughly the same amount of miles since they’ve been cleaned, so I can get a good comparison. Oh yeah one thing I didn’t mention on my original post, but the pics of the plugs I posted, were brand new 100 miles ago. I cleaned them about 50 miles ago. The other set have been in the car roughly 1400 miles and they both look the same when the come out. 😕

Gonna pull the connector off the upstream sensor tomorrow as well and see how much of a difference that will make.

But tightening the gaps did help some. So that’s a plus!
 

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So my wide band came in today and I installed it and took it for a drive. It seems I’m running lean at about 1/4 throttle or less, except for idle, and rich anything above 1/4 throttle.

1/4 throttle or less I'm between 15.5-16:1 and about 11.5-12.5:1 for anything above 1/4.

Haven’t tried unplugging the upstream sensor yet though.
 

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Maybe a stupid idea but do you have a different throttle position sensor to try? You guys are looking at really intelligent ideas (I've enjoyed reading) but it always seems like its the stupidest simplest things that give me headaches like this.

just an idea
 

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Maybe a stupid idea but do you have a different throttle position sensor to try? You guys are looking at really intelligent ideas (I've enjoyed reading) but it always seems like its the stupidest simplest things that give me headaches like this.

just an idea
Good thought! He did upgrade TB. I would have hoped he recal'd the TPS. Since he's OBD2, he can use his handheld scanner and watch TPS % with key on engine off, loosen the screws and start rotating it until it hits 0, then snug back down.

Gotta love generic OBD2 for some things when its available :)
 

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Maybe a stupid idea but do you have a different throttle position sensor to try? You guys are looking at really intelligent ideas (I've enjoyed reading) but it always seems like its the stupidest simplest things that give me headaches like this.

just an idea
Good thought! He did upgrade TB. I would have hoped he recal'd the TPS. Since he's OBD2, he can use his handheld scanner and watch TPS % with key on engine off, loosen the screws and start rotating it until it hits 0, then snug back down.

Gotta love generic OBD2 for some things when its available <img src="http://www.d-series.org/forums/images/smilie/icon_smile.gif" border="0" alt="" title="Smile" class="inlineimg" />

It’s not a stupid idea at all dude. But you’re right it usually is small stuff that causes problems like this.

And yeah I calibrated the tps when I swapped the TB’s out. But I’ve had one fail on me and one got smashed pulling the motor since then, so I’ve had to switch them a few times. It’s possible I don’t have this one calibrated correctly so I’ll have to check it when I get off work. And that’s also a damn good idea to use the scanner to calibrate it. I hate having to check the voltage while trying to adjust it.

Thanks guys!
 

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Soooo I just checked my TPS. And it’s off. It’s reading about 10.5% throttle fully closed. But I can’t adjust it anymore unless I drill out the adjustment slots. I think I remember having this problem when I installed it where I couldn’t get it to the exact voltage because it was already bottomed out. I cleaned the connector with some contact cleaner to make sure it wasn’t dirty and it didn’t affect it. Thinking I got a faulty sensor, which would be just my luck with all these cheap auto part store parts from China now a days. Do ya’ll think I should try drilling out the slots or just replace it out right?
 

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How much material do you have on the sensor right now to be able to remove excess from the slotted area?

If you take away too much, you might want to build a special set of washers using a bench grinder and actual washers to shape them into appropriate clamps be able to clamp down the sensor over more of the available plastic if you really need to remove a lot of plastic.

Try removing the sensor entirely, and rotating the shaft sticking out of the sensor manually towards the 0% position. If the sensor reaches 0% on the scan tool then its not the sensor that is faulty, it will just need to be adjusted/adapted correctly (however you manage to accomplish this haha) to the throttle body in question.

Rep for [email protected] :)
 

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I might need to take away about 1/3 of the material that’s there to make it work. I’ve got drawers full of nuts/bolts/washers so I can make anything that I need to get it mounted.

Ok I’ll check it and see if I can get it to zero out first. I’m not one to normally just say try and fix something like this. The sensor isn't that expensive so I’d normally just replace it. But I’ve had 3 sensors on it in the last 2 years. I’m tired of spending the money on stupid parts. Like I’ve gone through 4 starters in 5 years with this damned thing. The solenoid has gone out on every single one of these things and the current one is starting to go as well. Next one will be an oem one through the dealer, but they’re backordered with no date that it'll be available. 😑

But I’m gonna go remove and check that now. I’ll update on this soon. Still don’t know if fixing this will fix my problem, but it’s a step in the right direction. But I’m pretty sure it’ll get rid of my high idle at least lol.

And yes. Much thanks to [email protected] for pointing this out!
 

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So upon checking the TPS, either way I adjust it, it won’t read 0% and 100% at the same setting. But free from the TB it will. The TB doesn’t have enough movement to send the sensor through it’s whole range. Is there a way to adjust that?
 

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throttle stop screw backed out enough to get to 0? throttle cable short enough to get 100?
 

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throttle stop screw backed out enough to get to 0? throttle cable short enough to get 100?

Yeah they are. Stop screw is backed all the way out and the cable will pull it all the way. Tried pulling the stop screw out more but The TB won’t adjust any farther than it is now.
 
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