5lbs vacuum at idle

[joe sobo]

i just got my engine back in the car and when i start it, the idle vacuum is at only 5 . also, the car will rev to 38-4600 rpms and stay there hot or cold ive checked throttle cable, and all sensors , did boost leak test and found none

any ideas?????????????????????????/

 

[hdoerr]

where do you have the boost source tapped?

 

[robbo185]

check your timing

 

[joe sobo]

same spot as before my rebuild......... t-ed of of fpr and intake

 

[hdoerr]

Try using the vacuum source at the throttle body. I believe it is the one closest to the valve cover on top where the elbow meets the throttle body. If possible tap the compressor outlet pipe or J-Pipe. When I lost the nipple on the stock outlet pipe after the FMIC install I had the same problem. My boost gauge was reading 0 at idle and only moved when reving. I had the source at the manifold pressure as well so try using what I stated and see if you then see -20 to -15 as I did when I changed.

 

[joe sobo]

i mhave it in the same spot as before my rebuild. before my rebuild, i had almost 20

 

[robbo185]

did you check your timing?

 

[joe sobo]

no, i havent checked my timing. i only did the rotation thing when the engine was being assembled

 

[robbo185]

check it then get back to us.

 

[M3BEAST]

Align the CAS notch on its mark. May be 180 opposite and the timing is too far advanced?

 

[bento]

Most likely is your ignition timing. I had the same situation. My car idled at -12 vaccum. My ignition timing was off. Car wouldn't idle right, it would fluctuate up and down, lean idle and very rich wot.

 

[joe sobo]

i just got done checking the timing on the car........ all the marks are aligned. the oil pump is not aligned, but i dont beleive that has any affect on it for i have no counter balance shafts.



any more clues??????????????

i did take a plug out to check tdc, and the plugs are jet black from running so rich. but that wont make the car rev to3800-4500 rpm would it?

 

[joe sobo]

i finally had another chance to go over the car...... the car is running extremely rich,, the plugs are black so its just dumping fuel into the motor,, but i also realized that the car has only 2 lbs of vacuum any clues??????? but when the engine rpms jump and stay at 4800 rps, the vacuum is at 20 any causes?

 

[knochgoon24]

Look for a cracked or loose vacuum hose. If the leak is bad enough, the engine might not be able to keep up.

 

[absolute_DSM]

Did you break in the engine yet? If not that, I think you have a big leak. Boost leak test it.


EDIT, checked your profile. Do you have your global and deadtimes set for your injectors in DSMlink?

 

[6bolt2gdsm]

Did you break in the engine yet? If not that, I think you have a big leak. Boost leak test it.


EDIT, checked your profile. Do you have your global and deadtimes set for your injectors in DSMlink?

I agree this sounds like you have a vacuum leak somewhere vacuum should be anywhere from 17-21 at idle and 0 at WOT