Rough idle and sputters at 4k

[thakingcb7]

Ok so I just bought this car last Wednesday and have been fixing little problems I find. But now I'm a little stumped as to what my next moves should be. As the title states... the car stutters at 4k and also has a rough idle. There no boost leak and I believe all sensors to be in working condition as there are no CEL's. Mods are: E316g, 3in turbo back exhaust, hard upper pipe, and RC 550's. I'm open to all suggestions.

 

[catomlinson42]

I had roughly the same problem once and it turned out to be a loose wire on the CAS because i have 6 bolt swap and didnt use one of the great harnesses they have out for sale nowadays. Id also check plugs and wires and possibly coil pack...or ecu.or 02 sensor. Good luck

 

[oneslowwdsm]

Are you tuned for those 550s?

 

[2gmitsueclipse]

Here are a couple of thoughts.

• How do you know there are no boost/vacuum leaks?

• Have you completed any logs as you have larger than stock fuel injectors? Must have something to tune/monitor with.
• What does your AFR look like during idle and when sputtering begins?
• Have you checked/replace your spark plugs with proper gap?
• Are the plug wires in good shape with no cracks?
• I would also consider changing the fuel filter as a maintenance item with a new car purchase.

 

[thakingcb7]

No tune or anything to tune with YET... but plugs and wires are new with proper gap. Also the new fuel filter should be installed within the next couple day's... it's too damn cold for that right now. I have a set of 2g 450's I was gonna throw in for now but again, it's too damn cold. As far as no vacuum/boost leaks... i checked at all lines and seals on the intake with carb cleaner and idle stayed the same and the boost holds at a steady 11psi in all gears.

 

[thakingcb7]

Oh and as far as AFR's... exhaust smells normal at idle but when you hit the 4k sputter there's a hint of fuel and the smoke is pretty black. I'd imagine whatever the problem is it's causing the ecu to dump fuel.

 

[2gmitsueclipse]

I think you have your answer then....Your ecu assumes you have 450's on the car, so it is adding fuel accordingly. New filter and the 450's should be good until you get a wide band and way to log/tune. The Carb cleaner trick will work for vacuum leaks, but not for positive pressure leaks (boost leak).
Make/buy a proper tool to perform this job and test:

http://www.vfaq.com/mods/ICtester.html

Here is how I built mine:

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How to use it:

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[thakingcb7]

I'll throw the 450's in when I get time and see how it goes.

 

[thakingcb7]

So I just got back from putting the 450's in and test driving... the 4k stutter is gone but the idle appears to have gotten slightly worse. Any idea's? Plugs and wires are new and properly gapped for those just joining us in this little adventure.

 

[2gmitsueclipse]

Try new plugs with correct gap....I do not know how long you were running that rich. See how that helps. After that, boost leak test with attention to throttle body and fuel injector seal areas.

 

[thakingcb7]

Plugs should be fine... i only drove it half a block on the new plugs before swapping. I'll probably have to wait til the weekend to do a boost leak test but I'll give it a shot

 

[thakingcb7]

Just a theory but... would 2 ground wires not being hooked up cause this? I found 2 down by the transmission that aren't hooked up. Also, there's some long gray wire that appears to go into my o2 sensor harness that isn't hooked up... real thin like 22 gauge maybe. Any ideas on what it is?

 

[2gmitsueclipse]

Having poor/not connected grounds can cause all kinds of problems. Those should be addressed and not sure what your loose wire is by the o2. May want to trace it. Also make sure the ground from the intake manifold to the firewall is hooked up as well.

 

[thakingcb7]

The loose wire was ran behind the engine and wrapped around the strut tower brace... but I'll try to get them grounds hooked up in the morning and see how that goes. I appreciate the help man. I dread having to figure out wiring nightmares.

 

[thakingcb7]

So I fixed the grounds and went for a short ride. The 4k stutter is still gone... but it's now got a 4500 stutter. I haven't had a chance to build a boost leak tester but I guess that'll have to be my next step. The more I look under the hood, the more I start to lose motivation. Every where I look there's at least one wire taped together.

 

[2gmitsueclipse]

You may want to invest in a multi-meter, soldering iron, decent wire cutter/strippers, and shrink tubing. One at a time, you could take the tape off of the wire and see what mess is made of the wiring. If tape was used, the PO likely half-a$$ed the rest of it as well. There are plenty of u-tuber videos that walk you through the relatively easy process. Get some extra wire to practice with as well.

 

[thakingcb7]

I can solder well enough to get the job done. I just don't have a place to do it and these single degree temperatures are a bit too much for me right now. Any idea where I can find a tube to get welded onto the intake pipe so I can recirc the bov?

 

[thakingcb7]

Haven't been around for a little while but I did discover this awesomeness

 

[oneslowwdsm]

Are you absolutely sure that is at TDC? I know you are supposed to rotate the engine a few times before checking timing marks.

 

[96BoostedGSX]

Haven't been around for a little while but I did discover this awesomeness

Wow! Looks like your timing is off by a tooth. Is your car still running since your last update?

 

[thakingcb7]

Still runs and still has the sputter. I'm positive it's TDC... i always stick a steel rod in the spark plug hole to verify and I turned it over 4 full rotations

 

[AllanL]

time for a timing belt job?

 

[inthemidst]

Definitely off timing by a tooth on each.

 

[thakingcb7]

My brother's picking the car up and doing it Tuesday while I'm at work

 

[96BoostedGSX]

Hopefully this should fix your stuttering issue. Get the whole timing kit. Especially replace that tensioner. Good luck man hope it all works out for you. Let us know.