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misfire and low vacuum @ idle

5.5K views 9 replies 6 participants last post by  whitegst97  
#1 ·
my car is idling low (600) since i replaced my head gasket last weekend, it misfires and the vacuum is at 12-14 in Hg. before i took the head off it idled at 1000 and 16-18 in Hg. i've checked all of the vacuum hoses and replaced a few but nothing seems to help. my ex manifold is leaking a tiny bit at the head, could that cause the crappy idle?

thanks
marshall
 
#3 ·
i am not sure if that can cause idle problmes
but you should definetly try to fix the leak
at the manny. This will definetly rob you a little
on the power side and can cause the misfiring
maybe, but you should check the spark plugs first,
wires and just doulble check any other leaks.
Just run through all the hose connections first, clamps
there aren't that many. Then check the vacuum lines
like you said again. But i am sure this is an
easy fix, tighten the manifold and check the plugs
and i am sure it will be solved. Why is your manny
leaking, did you strip one of the bolts??
 
#4 ·
thanks for the replies.
when i was taking the ex manifold off, two of the studs snapped and i didn't feel like fixing them because i just wanted to get my car back, it had been sitting for four weeks...they snapped inside the head so it's going to be a pain drilling them out...any tips on the process would be appreciated.

marshall
 
#5 ·
My bad, I thought you said it was an intake manifold leak. The exhaust manifold leak will rob power, spool up, and cause a little noise. The problem you are describibg sounds like a vacuum leak though. Check all your hoses for leaks. Also, try putting new plugs/wires in. Considering that this problem has only arisen since you did your headgasket, you should consider everything that you had to remove to do the job. Check for leaks around the intake manifold, also, alot of times plug wires get damaged if you dont remove them carefully. Check to make sure that the outlets on your coil pack correspond with the correct cylinder.
 
#6 ·
Sorry i know thios is an old thread but i just didn't want to start a new one when i found this one. Well i checked my car with a datalogger and an error code came out "P0300" meaning misfire in multiple cylinders. Can any one help, what could b causing my misfire, i have Accel 8.5mm wires and Bosch platinum, regular ones. But i heard the boschs aren't very good, they are quite hot. But what could be causing my misfire. Also some more info if it helps, when cold or in the mornings when i start the car out the exhaust it spits out like black moist dust. Any help?? Thanks you
 
#7 ·
marshall...

Take the top timing belt cover off and check that the timing marks are aligned correctly. I have seen cases were the exhasut cam is off by one tooth resulting in low idle and vaccum reading just like you'are describing yours.


By the way never use platinum plugs on our cars. They simple don't like them. Try swapping a set of NGK BR6-ES ones gapped at 0.030" and see if the misfire continues.
 
#8 ·
whitegst97 said:
Sorry i know thios is an old thread but i just didn't want to start a new one when i found this one. Well i checked my car with a datalogger and an error code came out "P0300" meaning misfire in multiple cylinders. Can any one help, what could b causing my misfire, i have Accel 8.5mm wires and Bosch platinum, regular ones. But i heard the boschs aren't very good, they are quite hot. But what could be causing my misfire. Also some more info if it helps, when cold or in the mornings when i start the car out the exhaust it spits out like black moist dust. Any help?? Thanks you

Get those platinum plugs out RIGHT AWAY and throw in some NGK BPR6ES or BPR7ES's. Platinum plugs run waaaaay too hot to be used in our motors especially under boost.
 
#10 ·
Man im so frustrated but It'll pass, well i installed my NGK 6 and gapped them to .030" . I don't know if i did it right but i beleive i did, these plugs have two little metals on top of the spark carbon thingy, and well i gapped them by sticking the gapping gauge between the carbon and the metal and taking it to .030 and then the other space between the carbon and the other metal thing. I hope you understang what im trying to say. Well the CEL is still on and right after i installed them i started the car and damn spitting moist dust out the exhaust, which i assume is unburned gasoline. Well What could be my misfiring problem that was the error code that she datalogger showed, a P0300, which is misfiring in multiple cylinders. Any one please help.