RB25DET S2 driveability issue

[Motorhead]

Have an S2 RB25 in my Zenki S14, it idles perfectly, revs perfectly. Can pull out of my parking spot and slowly pull out. But it won't slowly accelerate, maintain speed on flat ground, etc. It spits and coughs and acts like it's running out of fuel (wiggle foot on gas with no effect) and then when your foot is deep enough it'll spool and pull hard. Have changed plugs just a few minutes ago, from Autolite XP's gapped at 1.2mm and replaced with NGK R's gapped at .9 with no change. About to pour 108 octane booster and change the fuel filter and see if that changes anything because I'm thinking now it might be bad gas, no idea how long it has been sitting. Thought I'd ask if anyone could help.

[Motorhead]

66637

Yeah, think I found my issue. What do you guys think.

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[supersayianjim]

I think it's time for some ls truck coils the swap is easy and you will thank me. you can see hos to do it if you look at the last 3 pages in the work log in my sig link!!

[Motorhead]

LS truck coils? Could you explain that a bit? I'll see if I can find it.

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[Motorhead]

Eh, I dunno if I'm down for doing all that modification and added expense. I'm just gonna try to find a set of S2 Coilpacks and replace them. Fun fun fun

[RB25GUY]

its gonna cost more money to find those s2 coils for a resonable price all you gotta do is a coilpack harness swap i believe with the ls1 coils and they are just as good as splitfire coils without the heavy dent on the pocket trust me youll thank jim and i later!

http://zilvia.net/f/engine-tech/462323-ls2-truck-coil-upgrade-rb25.html

[Motorhead]

Trust me, I'm not knocking what you guys are saying... I am totally down for an upgrade, but I just found a couple sets on here for 100ish bucks and I'd rather stay factory while on a budget. This seems like a really awesome thing to do in my spare time later though.

[fliprayzin240sx]

S2 coils are worst than S1 coils. Start off by double checking if you are having spark issue. Take the plug out, put it back into the coilpack, ground the tip to the head and crank the engine. You should see it spark. Also, gap your plugs down to .030~.028.

Then double check your base timing and TPS voltage.

[Motorhead]

S2 coils are worst than S1 coils. Start off by double checking if you are having spark issue. Take the plug out, put it back into the coilpack, ground the tip to the head and crank the engine. You should see it spark. Also, gap your plugs down to .030~.028.

Then double check your base timing and TPS voltage.

Are there a couple how to's or anything to check my base timing and TPS voltage? I'm assuming I'll need a volt meter?

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[fliprayzin240sx]

Google "RB25det timing adjustment" and "RB25det tps adjustment"...not exactly rocket science...

[Motorhead]

Oh it's that easy? Stand by then.

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[33jrod33]

My solution was cleaning my injectors. At times during driving, I would have to "feather" or light tap at the throttle to gain speed. I'm May give this Ls coil swap a try. What do you know cars torn apart anyways lol

[Darius]

Save yourself the trouble and just upgrade to LS coils. Stock coils are almost 20 years old now, so you might as well upgrade if you are going to spend any money. Plus, LS coils are less expensive. Win-win!

[supersayianjim]

^^ listen to the man!!

[Motorhead]

I'm down to upgrade to LS coils, but I'm mote concerned with a fix, rather than a mod.

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[smoked240]

Not only will the ls coil packs fix you're problem you'll have a nice mod done. When I upgrade my coils I'm going ls. Way easier to find if you need to also.

[Motorhead]

I'm not real keen on throwing parts at it.

Anyone know a way to test them? Without throwing a known good set in? Don't know anyone with an RB to swap with for a few minutes.

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[Sforteen]

I don't think you have a coil issue.. Your symptoms aren't consistant with weak coil packs..

Id check ignition timing, TPS, MAF, boost leaks etc.

[smoked240]

There is a chance it's not the coils but to be honest you'll be replacing those coil packs one day. Sooner the better.

Have it running in a very dark room, I'm saying like pitch black, with the coil pack cover off and watch around the coil packs for arcing. You could grab a screwdriver with a good rubber handle and poke around the coil packs and see of you can get it to arc. You don't gotta get rough with them though it's not like they owe you money haha.

Honestly Google is your friend, anything you want to know about the rb's will be in there.

[nyc240sx]

its probably running super rich check your a/f ratio..what tune do you have on it?

[Motorhead]

Supposed to be 100% stock as far as I know. Has an innovative wideband and a synapse recirc nov and a freddy intake manifold with a straight pipe.

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[smoked240]

I don't think you have a coil issue.. Your symptoms aren't consistant with weak coil packs..

Id check ignition timing, TPS, MAF, boost leaks etc.

Did you even look at the picture he posted? Second post down. That's clearly a burnt coil pack.

OP, now you gotta figure out if heat from the engine/turbo caused that or if the coil pack itself did.

[Motorhead]

The turbo is fairly bare and unshielded. Probably going to turbo wrap that in the future, nothin there to absorb heat.

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[smoked240]

The turbo is fairly bare and unshielded. Probably going to turbo wrap that in the future, nothin there to absorb heat.

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Yup same with mine. Not such a good idea to do but I like the cleaner look. Do you run with the coil pack cover on? I know that traps a lot of heat and cutting some nice holes in the cover will help. I machined an aluminum one in class and it works nice but gets really hot.

A brake booster shield would be a good idea one day too. The rb's in an s chassis tend to trap a lot of heat. Have you looked into the hood mod? a spacer is fitted to the back of the hood where it mounts and raises it to help pull heat from the engine bay.

[Motorhead]

Eh, I just bought the thing, it didn't have the cover installed when I picked it up, but it was in the back seat -- like he may have just taken it off.

I really like the little tutorial and the custom center piece in that one link for the LS pack swap, but... yeah.

Booster shield would be a huge priority, exactly what I was thinking.

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[smoked240]

Eh, I just bought the thing, it didn't have the cover installed when I picked it up, but it was in the back seat -- like he may have just taken it off.

I really like the little tutorial and the custom center piece in that one link for the LS pack swap, but... yeah.

Booster shield would be a huge priority, exactly what I was thinking.

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That makes me think the previous owner knew about the coils maybe? Or knew about the trapped heat. I would do the ls coil pack swap if you can swing the money. You'll thank yourself later. You might be able to pick them up cheap at a junk yard who knows.
I would do the hood mod too. It raises so little in the back you hardly notice it, I think. Helps keep the engine bay cool too.

[Motorhead]

Yeah it wouldn't surprise me. Not that I think he was shady, he went out of his way for me over the title (which he forgot to get before I showed up)... so I don't really wanna throw him under the bus, I just think he didn't really know a whole lot about the car. Claimed he built it, but in the same breath claimed it was all stock and felt like 350hp. So... you can kinda understand that while he wasn't exactly a super knowledgable guy, he wasn't a terrible guy. Anyway... regarding your hood-raise mod, I'm totally down for that too... if only for the short run, because I had intentions to replace the hood with possibly a battle style vent towards the front to let the air out from between the engine and Rad. It's a crap hood already on it, and I figure if I'm gonna replace it anyway, might as well make It a bit more functional.

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[smoked240]

Yeah it wouldn't surprise me. Not that I think he was shady, he went out of his way for me over the title (which he forgot to get before I showed up)... so I don't really wanna throw him under the bus, I just think he didn't really know a whole lot about the car. Claimed he built it, but in the same breath claimed it was all stock and felt like 350hp. So... you can kinda understand that while he wasn't exactly a super knowledgable guy, he wasn't a terrible guy. Anyway... regarding your hood-raise mod, I'm totally down for that too... if only for the short run, because I had intentions to replace the hood with possibly a battle style vent towards the front to let the air out from between the engine and Rad. It's a crap hood already on it, and I figure if I'm gonna replace it anyway, might as well make It a bit more functional.

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Yeah he probably just removed it cause of the heating issues. Hell ya man I'm in the same boat, my hood is fucked and is kinked in the middle on both ends so there is a hump in the hood :/ it might be right around 300hp. Hard to say until it's dyno'd.

[Motorhead]

Wanna know something funny? After all the sensors and ECU, etc checked out just fine... and a better-mechanic-than-I friend who had the car for a few weeks... apparently it having a WS harness, no one thought that the wrong TPS connector was plugged in.... the harness had two.

I feel like a moron.

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