New Z problems

[sawyer's720]

I picked up a 76 280z about a week ago that hadn't run for five years or so. i replaced the fuel pump because the one that was there was burnt out. new fuel filter, and all the tune up stuff. got it running and now that it has run for a while it seems to run pretty nice once it gets warmed up a bit. but if i try to rev the engine without load and put my foot down about 1/2 way or more then i hear a loud popping sound coming from the front of the engine compartment. i have no clue what it is. it only does it when it has no load on it. while its driving i dont seem to have that problem at all.

one other question. i need to rebuild a driver side wheel cylinder and i was curious about the difficulty. i've never done it before and i dont know what id need to replace.

thanks for your help guys. i really appreciate it.

[evildky]

the popping sounds odd, I'd pull the cam cover and adjust the valve lash and make sure the chain guides aren't flopping around or anything

as for the wheel cylinder, I assume you mean the rear, it's pretty simple but I if I were you I'd try locating the backing plate for a 77-78, they wheel sylinders are still availble and cheap and you get a double sided wheel cylinder for more efficient braking

[sawyer's720]

vavle lash needs to be adjusted for sure. im betting that will fix the popping problem.

your idea to change the backing plate is great! there is a 77 at the junkyard maybe i can get a hold of the back end. are the shoes different? i'd assume they are. im not trying to skimp my way thru it. just a curiousity.

also, i've got a miss. when i pulled the plugs the 5th cylinder plug has some oil on it and the sixth cylinder plug had just a hair. i don't know if im missing vac lines or anything because my chilton doesn't have the diagram. but i doubt thats what's causing my miss. any imput on that would be great. i plan on puttin in a rebuilt engine in once i get my school funds. i just want it to run a little better before i pull it.

[evildky]

the pads are the same IIRC, you can compare part numer on many parts sites, rock auto even has an "also fits" button, the wheel cylinder backing plate and hardware as well as the hard line that leads from the soft line to the wheel cylinder

as for the oil on the plugs, most likely it's a valve stem seal, most of the vac lines have to do with emissions aren't a big deal, the most common issues wiht the 280's is the injector clicps and wire leads getting brittle and breaking of the rubber hoses the leads fomr the afm to the tb dryrotting and leaking

[sawyer's720]

well now i've realised that the popping sound is actually a back fire thru the intake. it has been happening often while driving. half pedal or more at low RPMS 2300 or lower causes the back firing. timing issue probably? it runs great up past 2300 until about... 4500 then it falls on its face.

[evildky]

76 had the cost start injector IIRC, might try disconnecting it just in case it's overfueling, and it's always a god idea to verify ignitin timing

[sawyer's720]

sorry i haven't updated. i replaced all six injectors apart from the cold start. i left that alone. it runs like a champ, no missing at all but i was wondering if the stock cam for a76 280z was mild? because it's got a pretty lopey idle. i'm betting it's an ignition problem but i just wanted to pick brains. thanks guys.

[evildky]

all the stock cams shoudl have a smooth idle, if your idle is lopey it's likely a miss, could be due to mal adjusted lifters, bad injdctor clips, fowled plugs, bad chts etc

[sawyer's720]

my valve lash is off by a couple thousandths on most of the lifters. could that cause the lopey idle? i'm replacing the plugs with some NGK's because i hate autolite's. after that is done tomorrow i'll update to tell how it went. what is the chts?

[evildky]

I doubt your valve lash is out enough to cause idle issues, most likely you have a fuel or spark issue

also not a fan of autolites, but I generally opt for the japanese made denso's over the american made ngk's but thats just a matter of personal prefference

CHTS = Cylinder Head Temperature Sensor, it's one fo the sensors located on the lower thermostat housing on early injected L6's (they later moved it to the passanger side fo the cylinder head) it's the connector iht 2 wires that looks like an injector clip, if it's bad or disconnected the engine faults for extra fuel which can cause flooding

the emissions control such as the egr idle soleniod etc are possible issues as well as a simple vac leak due to bad ruber hoses between the afm and the tb, also a dead spot on the afm can cause isle issues

[sawyer's720]

i cleaned out the EGR valve, ton of carbon in there, new plugs, set the valve lash, still idles lopey. i dont know how i would check to see if the CHTS is working correctly so any help would be appreciated, it does run better but still lopey. i was also wondering if a leaky exhaust manifold could cause any performance loss or if it would simulate a vacuum leak.

[evildky]

to test the chts, with the car warmed up and idling, unplug it, it should run a lot worse and ro die, if no change is noticed you have a bad chts

are you sure the car is idling on all 6 cylinders? you cna unplug one spark plug at a time and see fi the idle changes, if one cylinder does nto change it's nto firing forwhatever reason, bad plug, wire, valve, ring etc

and exhaust manifold leak will either sound like lifter clatter and or just be really loud, the bigger the leak the more it can hurt performance btu it shoudn't cause a lopey idle

[sawyer's720]

Turns out I have a HUGE vacuum leaks between the intake manifold and the head, replacing gasket and and testing tomorrow. sprayed carb cleaner at the seams and it idled smooth for a few seconds. Also, smog man says i need to replace the cat and the piping on the way back to the muffler. good opportunity to put in a new cat back system but i was curious about cat converters. Do I have to use one specific to my make and model? i know it has to be california ARB legal but i wasn't sure if i could just throw a cat designed for a ford on and be done with it. they are significantly cheaper.

[evildky]

cats are generally universal, in cali? dunno? chances are MSA sells a cali legal exhaust with cat

[sawyer's720]

MSA's online store doesn't have Cats listed. but thanks for answering about it being universal, i thought is was. also do you know if MSA's cat back kit is 2.5 all the way back or the stock 1 7/8?

[evildky]

thei cat back si whatever diameter they advertise it as, if you call and talk to a human they can give you all the info you want and might even have less popular smog legal kits, and if you tell them you are in a Z club sometimes they discount the price

[sawyer's720]

oh ok awesome evil, thanks.

also, after putting the car back togehter is seems to run a little worse, i think it's electrical, i know i put everything back where it goes tho. The only problem that I ran into was that upon taking the manifolds off i couldn't pull one of the devises on the upper thermostat housing so I cut the wire planning to solder it back together. upon putting it back together the wire snapped off of the sensor itself. There are four different things plugged in to the housing, what i cut was on the top row on the driver side. it only has a positive wire, which i broke, and a negative that grounds to the thermostat housing. I originally thought this was my water temp sensor but my gauge is still reading temp. Any help on what it could be that i broke would be helpful, i can't seem to find it in the chilton or the FSM.

Thanks!

[evildky]

should have 3 sensors/senders in the housing, the single wire is the sender for the temp gauge, the other 2 are sensors, one tells th ecu the engine is warm and to shut off warm up mode, the other is the thermotime switch for the injector cooling fan, which might have been removed, many people just leave them off, they are supposed to help prevent vaporlock

[sawyer's720]

well there are four different sensors in the housing. The bottom two both have clips like the fuel injectors and the two on the top have just wires directly connected to them.

[sawyer's720]

according to what i read in the FSM it is the Water Temperature Switch. would that have alot to do with overall engine function?

[evildky]

the 2 that look like injector clips are the chts (cylinder head temp sensor) thats the one that effects how the engine runs, it tells the ecu when the engine is cold and so it adds lots of extra fuel, if it's bad or disconnected it will run like crap to the point of flooding the engine, the other sensor taht looks like an injector clip the the thermotime switch, thats the one that goes to the injector cooler fan that you may or may nto still have, if you do it's fun when all the ricers come look under you hood and ask if it's a turbo, one fo the oens wiht 1 wire is for the gauge, and the other might have somethign to do with an auto trans or a/c for an auxiliary electric fan

[sawyer's720]

its a manual. when my mom comes home with the camera i'll post some pictures of it.

[sawyer's720]

its called the temperature switch. its basically only needed for warm up and its mostly un needed. fixed the rough idle. it was a fusible link. purrs like a kitten.