SR Stutter and miss when engine is warm?

[BlackZenkiS14]

Thanks man, I might give that a try!

[cbeuglas]

Z1 motor sports sells a knock sensor delete

https://www.z1motorsports.com/oxygen...ug-p-5580.html

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[cbeuglas]

I made mine using a 1 mega ohm resistor cut and soldered into my factory line using the knock sensor harness.

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[cbeuglas]

I will say this even with the knock sensor issue I never had the issue you are having. It was just sluggish and poor gas mileage. But that being said fix what you know is an issue first as it could be a domino effect.

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[BlackZenkiS14]

Thanks man, that might actually work!

[Javi802]

have you compression tested the engine?

[BlackZenkiS14]

Originally Posted by Javi802

have you compression tested the engine?

Nope, but I have no reason to assume that compression is bad. Although I plan on testing this this week.

[Javi802]

Get any closer to figuring out what the problem is/may be?


And have you taken it to any local 240 "specialists" in your area? If there are any, that is

[BlackZenkiS14]

Originally Posted by Javi802

Get any closer to figuring out what the problem is/may be?


And have you taken it to any local 240 "specialists" in your area? If there are any, that is

lol I am the specialist, and my best friend owns the largest/best race shop/fab shop/swap shop in the midwest lol

Here is what I've done most recently:

I rewelded my wastegate dump pipe, which at some point broke off this past few weeks...no fucking idea.

I also replaced my bad fuel pressure regulator, so I know that will affect it a bit, hopefully positively.

I also found a 95% broken wire (1 weak strand left, sorta) in the MAF wiring at the plug, so I resoldered a fresh wire into the pin, and re-pinned the connector. It was too late in my subdivision to fire up the car with neighbors close by, but I'll give it a test tomorrow.

Well, looks like it either didnt make a difference, or made a marginal difference. I dont think it was warm enough to get it to start really choking like it normally does. But it was smoother today after fixing those things. I'll have to get it out for a drive to confirm though.

I'm going to do a full run of tests on continuity and voltage of the MAF wiring next week probably.

I also get my actual own JWT ECU back tomorrow, so thats when I'll really start chasing down stuff again, watching NDS, etc...

I've already tried a couple different known-good Z32 MAF's, didnt make a difference.

Now, on the TPS thing, when you unplug TPS, it sends ECU into some kind of fail safe mode where it only uses certain sensors, and ignores others, and it changes timing. I gotta figure out what that correlation is, cause thats where my answer is.

[BlackZenkiS14]

I'm getting to the point now that it has to be something in the wiring, and I'm getting close to just buying a Wiring Specialties Pro harness....

[Kingtal0n]

Whelp, I just installed some HKS cams into my sr20det and now it also has a stutter and miss at idle. You sure you arn't just having large camshafts? ^ ^

[BlackZenkiS14]

Originally Posted by Kingtal0n

Whelp, I just installed some HKS cams into my sr20det and now it also has a stutter and miss at idle. You sure you arn't just having large camshafts? ^ ^

Mine aren't bad, just JWT S3 cams...260s IIRC

Is yours doing the exact same thing as mine?

[Kingtal0n]

Originally Posted by BlackZenkiS14

Mine aren't bad, just JWT S3 cams...260s IIRC

Is yours doing the exact same thing as mine?

Nah, I've tuned a few sr20det with S3 JWT. They are super mild and low-key, wont cause it to run poorly at idle unless its really lean, like 16.5:1.

[BlackZenkiS14]

Yea, I wouldnt have expected my cams to cause issue.

[Kingtal0n]

Originally Posted by BlackZenkiS14

Yea, I wouldnt have expected my cams to cause issue.

You dont have adj gears do you? If they were adjusted slightly off it could possibly give a more choppy idle. Come to think of it, my HKS cams have WAY more chop when my VTC is enabled. I never tried a set of S3 JWT cams on an S14 motor.

In any case, a miss is way different than a lope. A an idle "lope" has a distinct way of causing the engine to miss, in that it is random, your at 910rpm this second, the next you are at 840rpm, and them possibly back up or down more or less, depends on how the engine feels. It is a reliable, consistent, bouncing up and down of engine rpm more or less. I would know it right away when I hear/feel it.

[BlackZenkiS14]

I have stock cam gears, and an S13 motor. And the actual idle is fine, has a nice lope to it.

[Kingtal0n]

Originally Posted by BlackZenkiS14

I have stock cam gears, and an S13 motor. And the actual idle is fine, has a nice lope to it.

That worries me. The S3 cams I've installed in the past make no noticeable lope. Furthermore, if you are saying there is a lope, how can you know that this is not the cause of your missfire? When in fact that is partially what makes a lope erratic/ anticipated.

at this point I would say maybe you have some really old grind of S3 that is different from the new S3, or perhaps, you have something larger without realizing it. Did you ever check the Part# on your cams?

[BlackZenkiS14]

Yep, confirmed with JWT, its definitely an older style S3, prior to the HL availability.

[BlackZenkiS14]

Alright, starting down a new road here a little bit.

Help out:

http://zilvia.net/f/showthread.php?t=615034


Hey guys, I'm trying to track down some problems with my car, and I need some comparisons, I feel like my car isnt pulling enough vacuum at idle.

I have a built S13 blacktop with S3 cams. and I get 350 mm/hg at idle. How about you guys?

[daryl337]

13 is a little low, but it isn't absolutely terrible.
Mine runs in that ballpark, however I am running 270's not 260's.

Do you have adj. Cam gears? If so, you can try to adjust cam timing.

It could also be in the tune.... an overly rich engine tends to have a lower vacuum.

your best bet is if you perform a leakdown (make a tester out of 2 gauges, some brass fittings, with a .040" restrictor in between the gauges). Set an air compressor's regulator to 100 psi and then screw that bad boy into the spark plug hole of a cylinder that is at TDC.

Read the pressure drop from gauge 1 to gauge 2 and there ya go... leakdown. A nice bonus is you get to hear where the air is leaking to help you diag.