Problem! - Page 7

[ion] C2 · 11-12-2008, 12:57 PM

yeah right I'm going to go back to Midas and see if they still have my stock pile of rust manifold and downpipe so I can have him spend 2-3 hours of labor uninstalling and reinstalling a stock manifold and downpipe which will need to be welded back up if we did that

if it is the header, it's the EGR tube causing an inconsistency in the "sucking the gases out of the cylinder" effect and making that cylinder have an innacurate air-fuel mixture somehow. otherwise it's just four effing tubes on a flange, there's no reason it should cause issues like this.

what else could it be.

[ion] C2 · 11-12-2008, 01:52 PM

Also,

Alerosaint · 11-12-2008, 02:08 PM

Happy 190,000!!!

[ion] C2 · 11-12-2008, 02:18 PM

Silentalero · 11-12-2008, 04:05 PM

btw taking a picture at 70 mph ftw

[ion] C2 · 11-12-2008, 04:11 PM

ya with my camera phone, was hard to keep it smooth lol but i didn't want to miss this moment

Alerosaint · 11-12-2008, 04:14 PM

Hey it could have been 120....lol zoom zoom zoom

[ion] C2 · 11-12-2008, 04:35 PM

could've, my speed limiter is set to 254 lol

[ion] C2 · 11-13-2008, 10:11 AM

So anyone have any ideas?

Quote:

Originally Posted by [ion] C2

Detailed Summary
Ignore everything else.

This doesn't seem to affect anything but idle.. just tested WOT and logged in HPTuners to confirm: thing pulls hard, everything looks good. My cruising is perfect, my part throttle seems like it's always been.

Just idle. Seems when it thumps and may misfire there's a spike to lean real quick.

So.

What causes a rough idle (apparent misfire) but:
- runs fine otherwise as far as I can tell
- displays no codes
- no apparent vacuum leaks
- FPR, IAC, TPS are fine
- header nuts are tight, no exhaust leaks
- not O2 related
- kitty is nice and clear
- installed new spark plugs/coil pack housing/boots/springs
- ran a wire from the ICM bottom (between the ICM and IDI cover) to an IDI cover bolt to test if I needed the ground strap I removed 15 minutes before header install by swapping engine covers
- pulled fuel rail and reinstalled, ensuring the injectors were seated properly
- fuel pressure at idle is 48 psi

header --> downpipe --> flexpipe --> cat --> magnaflow --> piping --> dynomax --> outlets

All we did during the header install was:
1. unbolt stock downpipe
2. cut off pipe after cat just before magnaflow
3. removed strut bar, heat shield, coolant bracket, then stock manifold and gasket
4. installed header, had to remove oil dipstick and move the brake booster hose out of the way
5. tightened nuts, reinstalled dipstick and booster line and bracket
6. realized o2 bung location left zero room, so we plugged it with a threaded plug
7. welded o2 bungs (upstream & wideband) on the downpipe
8. bolted downpipe to header
9. welded flexpipe to downpipe
10. cut cat off of old piping, welded it to flexpipe and magnaflow
11. welded bung after cat for rear o2
12. reinstalled all o2 sensors

Doesn't make any sense to me. Unless the used Cobalt SS/SC injectors are bad or not firing properly for some reason...

Also, when I was at Speed Industry trying to get them to figure out what was up, my fuel pressure was 42 PSI, and then when I restarted it it was 48 (as it's been every time I checked). Why would the fuel pressure at idle be 42 all of a sudden? (It's always been 48 every time I look). Could that be related? I doubt it because it's always constant at idle, not fluctuating, and I always have great fueling at WOT.

rowdygls · 11-13-2008, 10:40 AM

Is Speed Industry able to test the injectors ?

[ion] C2 · 11-13-2008, 10:52 AM

yeah but my new engine is going in like, today or tomorrow so there's no reason to have them figure it out unless it exists after the engine goes in

Alerosaint · 11-13-2008, 11:07 AM

fuel pump maybe slowly giving in??? Maybe fuel pressure regulator intermittent???

[ion] C2 · 11-13-2008, 11:17 AM

doubt it, the FPR seems fine, i performed all the tests to check it and the rail pressure

and if the fuel pump was going it would have poor fueling at WOT

this only happens at idle... i'm questioning the injectors, since i had an idle issue when i put them in too, raised the idle from 600 to 750 to "fix" it like 4 weeks ago when they went in.

Alerosaint · 11-13-2008, 11:23 AM

yeah i remember that....try putting the stock injectors back in that way to know for sure... shouldnt take to long

[ion] C2 · 11-13-2008, 11:27 AM

i sold them

Alerosaint · 11-13-2008, 11:31 AM

damn....i wish i could loan you mines...i been trying to find a spare fuel rail to slot and trying to buy a used hptuner to flash....what about your 1st set that came with the car...it may not be able to handle the fuel for wot but they should be ok just to test the idle

[ion] C2 · 11-13-2008, 12:25 PM

I took some videos of the wideband gauge as well as the exhaust note, they're on my phone so it'll take a bit to convert them and upload them, but, I noticed something.

At even the slightest amount of throttle (like even 1%) at idle, the car will run SO SMOOTH. As soon as I let off the pedal and it goes back to 0% it goes back to the shaky sputter putt putt idle...

rowdygls · 11-13-2008, 01:00 PM

So what injectors are going in with the new motor ? If you think it's the injectors why not get them tested right away unless the built motor is using different injectors. Have you passed this by the speed shop to see if they have any insight ? If they are stumped, I could give a call to the guy that tuned my car to see if he has an idea.

[ion] C2 · 11-16-2008, 03:01 PM

Alerosaint · 11-16-2008, 10:55 PM

so you put water on it huh...lol