i'm running on 4 cylinders (cold)

[e_racer1999]

okay, my car's been terribly hard to start recently (72 240z) and i figured it was the carbs (being poorly adjusted). however, this morning (after tampering with my carbs last night) i did some experimenting and i am only running on 4 cylinders (at least when cold)

the ones that aren't firing are the #4 and #5 and i'm not sure why. my car's symptoms are, when starting in the morning, it takes a few minutes to get my motor going and when it does it idles very rough around 200 rpm. after trying to get it to idle higher (pulsing the gas) it rises VERY slowly, and if i try to get the revs over abour 1100 rpm it pops and drops back down to 800 (still very rough)

once it warms up a little bit it starts running a little better, but i have to ride the choke for the entire way to work. anyway, any help would be GREATLY appreciated, so that i can finally enjoy my car for all that it is! thx

-jason

[MikeW]

Are you getting spark to the non-firing plugs? If so, what do the plugs look like? Are they fouled with oil or fuel?

[e_racer1999]

Originally posted by MikeW

Are you getting spark to the non-firing plugs? If so, what do the plugs look like? Are they fouled with oil or fuel?

yes, when i pulled the cables they were clicking and i haven't had time to pull the plugs yet. i will when i get home. i'm figuring i adjusted my rear carb too lean, but that's just a guess

[1971rb26dett]

Yeah what Mike was saying....

The spark plugs will tell you exactly what is going on. I am having some problems with oil fouling lately. Symptoms are pretty much like yours. I haven't had the time to do a full checkup on her yet.

[e_racer1999]

i'm gonna pull the plugs right now. also, the exhaust manifold stud at the very rear is busted... would that cause me any drama?

edt: plugs look normal.... no oil fouling, gap appears correct, they are a little white, which i believe could be b/c i may be running lean (but they are pretty new plugs...)

[Bambikiller240]

i'm gonna pull the plugs right now. also, the exhaust manifold stud at the very rear is busted... would that cause me any drama?

The broken stud won't cause the 2 dead cylinders, but it will cause an exhaust leak that will get worse and worse as time goes on. It will cause the manifold to warp also, so it's best to resolve that issue before too much time goes by. BTDT.

[e_racer1999]

The broken stud won't cause the 2 dead cylinders, but it will cause an exhaust leak that will get worse and worse as time goes on. It will cause the manifold to warp also, so it's best to resolve that issue before too much time goes by. BTDT.

i know.... i'd really hate to burn a valve.. i don't have the tools to get the rest of the stud out of my head. what is an approximate price range i would be looking at to get it done?

[e_racer1999]

also, a little update: since the site's been down and the beginning of this post, i adjusted my carbs (not perfect, but MUCH better)

[Bambikiller240]

No idea on cost. I'd call your favorite machine shop, or a trusted repair shop and inquire. When I had a broken stud removed and replaced, it was done as part of a valve/head rebuild job and included in the overall bill.

[e_racer1999]

okay, thanks