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replaced head gasket....running a little rough off idle

wishihad1

NAXJA Forum User
hey everybody

I just did a head gasket for my friend. Everything actually went extremely well being it was our first time doing one. We took the head to a machine shop to be checked, and it was slightly warped. They resurfaced the head, and all is good with that. we installed everything back to factory specs also.

We start it up, and notice its running a little rough at idle, and maybe hot. I had a thermostat so we went ahead and popped a new one in there. not sure if it fixed anything or not, but it does seem to run a little cooler, and better. we broke the temp sensor during the install, so we cant really tell how or if its truely running hot or not. it isn't too bad, but isn't running as smooth as it should, and it accelerates fine, and revs great.

its a 96, and there was a 90 degree elbow coming off the intake manifold that was open and whistling, but we didn't know what it went to. we assumed it was a vacuum line, and putting a finger over it did improve how it idled.

Also the battery is fairly dead. it just barely starts it, and I only charged it enough the other day to get it started to pull it in the garage.

Tomorrow were going to replace the temp sensor to keep an eye on the temp and see if heat is a problem. also were going to flush the radiator, and fill with new coolant, and while were doing that leave the battery on a charger.

Although it is running 10 times better then it was when he brought it over, it still isn't at 100%.

any ideas?
 
That 90* elbow could easily go to the fuel pressure regulator. Then you would have a decent vacuum leak and uncontrolled fuel pressure.

Your plan of charging the battery fully, and replacing the temp sensor are a great start. Post a photo of the 90* elbow and the intake manifold area.
 
When the available voltage drops too low, below 9 volts, the electronics in the engine management start screwing up.

Get the battery fully charged, fix the vacuum leaks--there should be a sticker under the hood that shows your vacuum line routing--and post up your results.

Good luck.
 
Definitely get the vacuum hoses all connected. If still not running right, try a compression test--you could also have warped valves or crystalized rings.
 
I also had a cracked rubber vacuum "elbow" connector when I replaced my header last week. Went to the dealer for a replacement and discovered they will only sell that elbow with the entire vacuum line. I did not ask how much the line was and I'm not sure why I did not buy it.

To outmart the man, I cut off the elbow and used some rubber 3/8 inch fuel/vacuum line between the intake manifold and hard plastic vaccum line. It is not a perfect fit and I am getting a slight vacuum leak at that point, but it is better than it was and my idle RPM dropped from 1000 to about 800 with the hose in place. I plan to hang my head low and return to the dealer for a proper replacement.

I also got a noisy whistling intake leak during high rpm immediately after swapping to a Magnaflow muffler and eliminating the restrictive stock downpipe. Location was pinpointed to lower gasket by header bolt #5. My theory is the engine is breathing better and I have created more suction potential, thereby increasing the intake leak that I had, but never really noticed before. (Not sure if that is true, but I like saying "suction potential"). I need to retorque my manifold bolts, as I know my lower PITA bolts are not tight.
 
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