2g GST missing at idle..

[dyetrying91]

Before I start. CAR IS BONE STOCK.

So, I've been searching around the web and talked to quite a few different people in the past few days. Basically, my problem is as such. At idle it misses and the idle doesn't stay steady but floats from 800-1000 with vacuum at about 15psi. After accelerating hard and coming to a stop, the idle will go down to about 450-550 and vaccuum at 10psi, it recovers and comes back up within about 4 seconds after that.

Under acceleration is accelerates quick until the boost spools up. At about 14-15 psi it doesn't feel like 14-15 psi should. It holds boost so I'm pretty sure that it's not that. I'm running a boost leak test later on tonight to make certain. Oh yeah, I blew all the exhaust valves back in march due to timing belt snapping. Popped on a 2g head, cams are unknown as of this point, didn't look stock but might be, with 3g lifters and not sure what springs.

I've pretty much narrowed it down to a vacuum leak/boost leak or something in my fuel system isn't running right. It's not plugs/wires as I put on my 4th set of plugs and wires last week with the head. It doesn't miss under acceleration/boost, but when it is decelerating and at idle.

TL;DR

1. Car misses at idle
2. Accelerates normally, but boost doesn't hit as hard as it should
3. It isn't throttle cable/TB
4. No other obvious vacuum leaks, but I haven't ran a legit boost leak test yet.
5. Playing with the BISS does nothing to solve it.
6. Compression is good.
7. It's most likely either fuel or intake, im not sure where to start looking.

I'll grab a video of the idle/exhaust and engine bay in a few minutes and post it up in here.

UPDATE: just ran a compression test...

Cylinder 1 -- 161
Cylinder 2 -- 182
Cylinder 3 -- 179
Cylinder 4 -- 180

Heres a quick video. You kinda have to turn the volume up as my phone's microphone is a bit messed up.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/uSpbfP_0Cr0&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/uSpbfP_0Cr0&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[Dsmkauai]

Do the boost leak test!! Check for shaft play on turbo!! Clean your maf with proper cleaner from auto parts store, blow out air filter!! Also clean and check iac and have you got any mil codes yet.

 

[dyetrying91]

Do the boost leak test!! Check for shaft play on turbo!! Clean your maf with proper cleaner from auto parts store, blow out air filter!! Also clean and check iac and have you got any mil codes yet.

Turbo has 0 shaft play, it does leak a bit of oil, but its very very minor, ran like that for 60k miles. Cleaned the MAF earlier, as well as cleaned/reoiled air filter. Only code I have gotten since I finished the head swap was one random misfire code that hasn't came back since I wiped it 1k miles ago.

The 2 part epoxy is drying on my DIY boost leak tester as I type this.

 

[97-gst]

check your plugs and wires, my car was acting similar to yours and threw out the same code. I had bad wires on my COP

 

[dyetrying91]

check your plugs and wires, my car was acting similar to yours and threw out the same code. I had bad wires on my COP

Plugs and wires are less than a week old. I guess I can pick up some new ones this weekend and give it a shot.

 

[97-gst]

did it start missing after you changed them or before

 

[dyetrying91]

did it start missing after you changed them or before

When my timing belt blew, it somehow only damaged like 3/8 of the exhaust valves, after I popped a new belt on was when it started. I drove it like 1800 miles like that before I got a new head, and it still does it, only now the car actually drives like it should, except boost hits 16 psi, but feels like 4 psi and the idle is rough.

EDIT: Forgot about this video, this was after driving 2 exits on the highway to home depot, to get parts to make a boost leak test.

EDIT2: Ignore the taking back sunday playing in that video, also, my oil pressure is fine, I just need to fix the sensor.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/xmequfF6YS4&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/xmequfF6YS4&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[LiquidX]

You need to do a boost leak test first as I can already tell you have leaks. Next you need to check your mechanical timing and I'm assuming the valves were replaced and a valve job was done to mated to the head.

Check those and post results. Remember to use soap water for the boost leak test.

 

[dyetrying91]

You need to do a boost leak test first as I can already tell you have leaks. Next you need to check your mechanical timing and I'm assuming the valves were replaced and a valve job was done to mated to the head.

Check those and post results. Remember to use soap water for the boost leak test.

Completely new head with 3g lifters went in, brand new valves. Stock cams I believe, but im not sure as they didn't look the same as mine in the old head. It was ported and polished on both intake and exhaust side as well, as well as perfectly decked before I put it in.

Also, whats the easiest way to check mechanical timing? pull the top and bottom covers and rotate crankshaft until the camshaft timing marks align?

 

[LiquidX]

That would be the easiest. Make sure it all lines up. If you have a 1g CAS it could be 180* out as well. I can't check profile now as I'm on a phone but defiantly get the leaks fixed and check timing. If 1g CAS check ignition timing with a timing light.


I'm not sure if the 2g cam sensor can be mounted upside-down but if so that could cause issues as everything is reading off on the ECU in relatin to what mechanically happening.

 

[dyetrying91]

That would be the easiest. Make sure it all lines up. If you have a 1g CAS it could be 180* out as well. I can't check profile now as I'm on a phone but defiantly get the leaks fixed and check timing. If 1g CAS check ignition timing with a timing light.


I'm not sure if the 2g cam sensor can be mounted upside-down but if so that could cause issues as everything is reading off on the ECU in relatin to what mechanically happening.

Its a 2g, and yeah, 2g's barely even run if the CAS is put in upside down Just to confirm, the hatch marks on the cam sprockets should be pointing directly at each other and level with the top of the head correct?

Also, a stupid question, but since I'm new to DSM's, im coming from driving Bimmers, I don't have much experience with FI systems. How did you guys know there were leaks? The vaccuum at idle?

 

[banishedmunk]

If you use a straight edge all four marks should align with the cam sprocket dowels at the 12 oclock position

 

[dyetrying91]

If you use a straight edge all four marks should align with the cam sprocket dowels at the 12 oclock position

4 marks? the Vfaq only shows 2.

You must be logged in to view this image or video.

 

[banishedmunk]

yes the gears have slots in the 3 and 9 position on them but only one mark will be painted so that the gears can be interchangeable.

 

[dyetrying91]

yes the gears have slots in the 3 and 9 position on them but only one mark will be painted so that the gears can be interchangeable.

Didn't know that, never even heard that before.

 

[LiquidX]

Vacuum at idle with stock cams is around 20-25inHg. Running higher lift cams will lower your vacuum. I'm at roughly 13inHg with Delta 272 (HKS grind) cams.


I cannot find a diagram right now but if no one finds it, I'll dig one up later of the leakable bolt.

 

[banishedmunk]

the intake gear should be marked with white paint on the 9 o'clock position and the exhaust gear on the 3 o'clock position. but by aligning all 4 you gaurantee that the center marks are in the center and not off just a tad.

 

[simpleechris]

More than likely you have a boost leak!!! How are your o2 sensors? Do you have a cat on it? Also make sure that your ecu isn't burnt out or bad!!!

 

[dyetrying91]

More than likely you have a boost leak!!! How are your o2 sensors? Do you have a cat on it? Also make sure that your ecu isn't burnt out or bad!!!

o2 sensors haven't thrown a code yet. If fixing whatever boost/vaccuum leaks fixes it then i'll assume they are good, if it doesn't i'll check with my voltmeter.

Just ran the boost leak test. Only leak I found was at the BISS. A pretty large one, i'm gunna try to see what I can do about fixing that. Other than that, it's just mechanical timing to check really?\

I update main post too but..

UPDATE: just ran a compression test...

Cylinder 1 -- 161
Cylinder 2 -- 182
Cylinder 3 -- 179
Cylinder 4 -- 180

 

[dyetrying91]

Just an update.

I ran another boost leak test and found one at the BOV and one at the throttle body. I'll be taking care of both this week. Beyond that, does anyone have the 2g vacuum delete chart thing handy? The one that shows what to remove and how to the overall delete? It is entirely possible that I somehow have all my vacuum lines plugged in wrong.