:bulb:Hey. Im new to the forum (post wise) ive read a lot of stuff on here over the last year, never had to post until now .

So hello,

Anyways. i have an issue with my 78 280z l28 (cold air intake, 2.25 exhaust glasspack muffler) 5 speed (straight gears).

It is an arizona car and i need to pass emissions here so i can get my plates and registration.

I can get the car to run great under a load and WOT with no miss or studdering.

but my issue is idle.

It has a rough idle. clearly a miss and rich exhaust.

Ive taken it to emissions twice.

The first time i took it was bone stock. no cold air intake, no exhaust. nothing done to it. and it passed everything within spec at the load speeds.

BUT didnt pass at idle.

it failed only with high hydrocarbons. pass is around 250 and it was putting out 890.

so did a full tune up. plugs 45 degree gap, wires, cap, roter, cold air intake because my boots were broken and leaking air after the AFM. and 2.25 inch exhaust same cat (exhaust guy said it was still good) and same muffler (glasspack).

did some tinkering with timing (which i cant get the white mark on the pulley to show up on the scale on the block so i assume the timing chain jumped, stretched, or someone did something wrong in a repair) and replaced one of the coolent temp sensor connectors (one closer to driver side) because it was totally destroyed.

also tinkered with that big screw that is on the throttle body that lowers or raises the idle (also seams to make it idle smoother the higher the idle is, more rough the lower the idle is, its at about 1200rpms right now for the smoothest idle.. still has a miss and rich exhaust)

i took it back to test again and it failed WORSE. passed everything under a load just like last time, but at idle instead of it failing at 890 PPM's HC it failed at 1300 PPM's.

Please help me with any suggestons. i dont have a lot of tools or work space, and not a lot of money to take it to a mechanic.. if there is something i did wrong, or something i missed that is easy to check or needs a cheap tool to fix, adjust, or anything please let me know.

I have to get this thing passed by the 16th or i cant drive it! and its my only vehicle..

Thanks in advance!!!!

Edited July 12, 201014 yr by Shade133

First thing you do is Seafoam the motor.

forgot about that. put seafoam in the engine and gas tank?

ive ran 2 bottles of valvoline injector cleaner in it a while back before the first test.

Have you checked the adjustment of your throttle position switch?

i have messed with that a lot and it doesnt seem to make much of a change. sometimes it will iddle lower or higher and sometimes it wont do anythign. i have messed with that for a hour or more trying to get it to make a difference.

is there an effective way i can use a volt metor (i have a old school analog one) to test it and adjust it the right way?

ive also read something about taking it apart and re adjusting the points inside of it.

You don't have to take it apart to adjust it. Do you have a factory service manual? The procedure is in the Engine Fuel section.

no ive yet to buy one.. i cant find one here in the normal parts stores so when i get paid i plan on buying one online.

should the car run better if i unplug the tps? maybe send it in a limp mode or a guess mode

Here's a link to a 1978 FSM.

awesome! thanks a bunch. one other question. could i fix this issue by maybe a leakie injector. or possible my cold start injector. i was reading another post and it makes sense that my cold start injector could be leaking even when unplugged (which its unplugged)..

These cars aren't sophisticated enough to go into a computer controlled 'limp mode' or reduced performance mode. Either they run right or they don't based on condition/adjustment of the components.

EDIT: I would think that if an injector or CSV were leaking you'd have mixture problems in all ranges, not just at idle.

Edited July 12, 201014 yr by sblake01

These cars aren't sophisticated enough to go into a computer controlled 'limp mode' or reduced performance mode. Either they run right or they don't based on condition/adjustment of the components.

good because i hate it when comptuers go into limp mode. if they dont it leaves for better trouble shooting. like disconnecting sensors and reconnecting them to see if they work!

I agree with Mr.Blake-however, being in Phoenix,you will lose nothing by pinching off the CSV line.It is POSSIBLE(however remotely)that the CSV could be dribbling just enough to screw up the idle