engine cuts at full throttle

a couple days ago, my buddy tells me that im leaking some coolant. so i check it out, and its coming from the water pump area, but its only when shut off for more than 1 hour. ok. so i just decided to wait it out (i plan to do the timing, and water pup stuff come spring, i dont drive it in the salt..i mean winter). i kept the coolant full, and at a 50/50 mix. Today, i was heading to the grocery store, and my temp gauge went to half..it NEVER gets that high, i kept a real close eye on it, and 30 secs later, its on the H (hot, lol) and im like CRAP! so i blast the heater on high, and its blowing cool air (sounds like a t-stat). i just let it go, so i pull off to the side. it keeps getting a bit higher on the temp, and the air is still cool. hmm..so i decide to turn back (was only 1/2 mile from home) and just go slow. soon as i get to 10 mph, the heat gets SUPER HOT, and the windows get fogged up. eh?! the faster i went, the hotter it got, so i stayed at 10mph, and it sayed at 3/4 hot. got home, opened hood. coolant FULL. lines FULL, no collapse, no leaky from water pump. (wasnt about to pop radiator cap..but it was full to the best of my knowledge.) WTF?!?

ok now w out poping the rad. cap of you dont knwo for sure if ur radiator is full. The radiator works uder a 12-14 psi so when u have no collan/water and soor as u give it gas teh pressure rises and pushes teh left over water faster adn that heats up the heater core. Im prety sure if u didnt see a leak ANYWERE than most likely is that you head gasket is leaking.

I would know this from experience b/c 2 cars came through the shop w that prob and it happened to me

Good Luck

my guess would be clogged radiator,.. try flushing that beast out and see if it makes a difference..

best thing i found so far was to use CLR and completely take the radiator out and just let that stuff soak in for about 20 min.. then just swash it around in the radiator.. when i did it the liquid that i poured out when i was down was BLACK, and it was clear (with a greenish tint) when i poured it in

i did do a flush. that helped (used simple green, but CLR is a good idea..) turns out, i had some weird as crusty stuff in the lines?! it was white-ish in color. i flushed as much as i could...no probs..meh..

its been awhile since i posted anything here, glad to see place is still rocking, well i took the 86 silvia out of storage(winter is over here in NY) and have been driving for a few weeks, the problem is, when i mash the pedel to the floor sometimes the engine will cut off untill i let up about 30% on the throttle, also the tach sometimes drops to zero when im just crusing alone, sounds like an a problem with getting juice someplace, anyone else had this happen? thanks for your help...

When you are cruising and the tach drops to 0 does the car die too??  If not it could be you primary coil or the tach itself; but I have a feeling that it might be something to do with your primary coil.

a bit more information, no the car does not die when the tach is at zero, the car runs fine until pedel is WOT UNDER 4000rpm so basicly car cuts when second coil kicks in.... lack of enough power to the coils? im going to check all connections this weekend, any other ideas?

Bad primary coil.
Secondary coil is only used 0-4k RPM and when not WOT, otherwise it runs primary only.
Check your primary spark, plug wires, distributor cap, and firing order.
I\'ve had this problem before too.

Edit:
And actually, if your tach is dropping to zero, there\'s a good chance it\'s the primary side power transistor. But check the coil first (it\'s much cheaper to replace).

are the primary and secondary coils identical? can i swap them to see if one is bad? thanks

are the primary and secondary coils identical? can i swap them to see if one is bad? thanks

thanks for you help seishuku i swaped them and now the car runs fine, primary coil problem... summit just got an order for two blaster SS coils ;)

Yup, no problem. It\'s a pretty common problem on these motors.

Hey im a newbie to the forum and was having the same problem with my s12. now its fixd. just wanted to say thanks