ignition timing off?

[bento]

My boost gauge is steady at 10 mercury at idle constantly. Could it be the ignition timing off, or a boost leak? My engine is completly stock with 145.000 miles and full compression all across. I had 1 leak which was at my blow off valve, fixed it, but my vacuum is still at 10, will not change. I'm waiting till monday to do another boost leak test. Could ignition timing cause this?

 

[talon4lifetsi]

Is the car perfoming properly???

 

[bento]

Car runs good, but not 100 percent. Idle is a bit rough. When i accelerate above 1500 rpm's i get a slight miss throughtout the entire rpm. I'm getting a code for knock sensor. So i thought the ignition timing was off since it misses and my vacuum is constant at 10 at idle. It's got all new spark plugs, wires. e.t.c....

 

[talon4lifetsi]

Did you do a bost leak test??

 

[TSi_with_psi]

What RPM is your car idling at? If it is idling much higher then 750-800 rpm when it is warmed up, i would check for a vacuum leak. A stock 1G should have around 18-20 inHg at idle. Ignition timing can affect vacuum some, but not nearly as much as your cam timing. Check to make sure all your timing marks line up on the cams and crank. If you have access to a timing light, it would be worth checking.

 

[bento]

I didn't get to do a boost leak test yet. Have not touched the car since. I'm thinking it's the intake manifold gasket leaking. I took it out to clean the plenum while the car was stopped for 2 years and i reused the same gasket. (stupid me). I already got a new one. I will put it on hopefully sometime this week. And yes i have a timing light, i will also check my ignition timing if that doesn't do it. Valve timing is good. Crank, balance shaft, cams, they all line up good. I will keep you guys posted. Thank you for the help

 

[talon4lifetsi]

Turn the car on and spray carb cleaner around the intake mani. The idle will rev up when you hit the spot where its leakin.

 

[bento]

I did the intake manifold gasket and still got the same issue. I did a compression test.
cylinder 1 150
cylinder 2 149
cylinder 3 140
cylinder 4 130
this was with a warm engine, all spark plugs removed, and not opening the throtle. Just cranking the engine. It seems to be a bit low.

 

[bojanglesracing]

it sounds like a vacuum leak. Is it a stock gage your reading?

 

[bento]

Autometer gauge. And now my idle fluctuates from 1000 to 1500 rpms. The only thing i can think of is a leak at the throtle shaft seals. I hear a whistle sound coming right from the spring of the trothle body where the throtle cable hooks up to. I'm guessing it's the shaft seals. I sprayed it with carb cleaner but did not notice any change. I'm gonna take the throtle body out abd replace those orings on the shaft.

 

[ChrisGo]

I did the intake manifold gasket and still got the same issue. I did a compression test.
cylinder 1 150
cylinder 2 149
cylinder 3 140
cylinder 4 130
this was with a warm engine, all spark plugs removed, and not opening the throtle. Just cranking the engine. It seems to be a bit low.

Those are low.. Cylinder 4 is below the service limit. Did you do the wet test?

 

[bento]

Yes, i poured a bit of oil into the cylinder and the compression jumped to 210. It's telling me i have bad rings. But i don't think it's that bad. 130 is not that bad and i don't think would make the car run the way it's running. Bad rings wouldn't take vaccum away i don't think. I'm gonna do another boost leak test this week. See if i come up with a leak at the throthle shaft seals. Cylinders 1,2,3 were all between 140-150, it was just cylinder 4 that was at 130. This is a 7.8 compression ratio motor. At idle my wideband is reading lean. It's misfiring like if it's pre ignition.

 

[ChrisGo]

Yes, i poured a bit of oil into the cylinder and the compression jumped to 210. It's telling me i have bad rings. But i don't think it's that bad. 130 is not that bad and i don't think would make the car run the way it's running. Bad rings wouldn't take vaccum away i don't think. I'm gonna do another boost leak test this week. See if i come up with a leak at the throthle shaft seals. Cylinders 1,2,3 were all between 140-150, it was just cylinder 4 that was at 130. This is a 7.8 compression ratio motor. At idle my wideband is reading lean. It's misfiring like if it's pre ignition.

What are you reading with the wideband at idle? The service limit for our car's compression is 133 so you are just below that.

 

[rich3389]

Actually the service limit for 2g's is 127 psi, its right in the owners manual.

 

[ChrisGo]

Actually the service limit for 2g's is 127 psi, its right in the owners manual.

I was getting my info from the vfaq..

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm

 

[bento]

My idle fluctuates from 1200 to 1500 as if the isc switch is bad. My aem wideband is displaying lean at idle. If i give it gas than it's moves down to about 14-16 afrs but it sputters and misfires. I disconnect the isc switch and it idles steady at 1900 or so and afrs go to the 14s

 

[bento]

I just removed my isc from the car to test it with a ohmeter. It's specs ahould be between 28-33 ohms from coil to coil. I had over 36 in every circuit. I got a bad isc . Now that explains why the car is running rough and my idle fluctuating and surging from 1500-1900 rpms. I'm not sure if it has anything to do with or if affects my vaccum.