coldfire

iTrader: (1)

okay, i went from a 1500 RPM idle with BAD misfire, to a super smooth 750 (on my 89 NA). here's how:

1) i first made sure my throttle linkage and assembly were fine. my throttle cable was actually not sitting perfectly, so i just pulled on it a bit, put some WD-40 in there, and then seated in back in properly (or what looked like it). this didn't really did nothing

2) i proceeded to check for vacuum leaks. i THOUGHT heard a suction noise, but i couldn't find any leaks just visually and physically inspecting the hoses. i should have sprayed something to check, but if you read on, i probably don't have a leak anyway...

3) i proceeded to adjust my TPS. FSM says to get a new one, but whatever, you can adjust it on your current one. if you don't know how to do this DO A SEARCH, that's how i learned . initially the narrow range closed was at a stupid 2.4 K ohms, but WOT was perfect. so i adjusted it down to 1 K, although it took me a good 6 or so turns, and apparently you shouldn't have to turn it this much. i checked full range too, and it was perfect after doing this. as for my idle, it had come down a bit to about 1000 rpm, and the misfire had disappeared quite a bit.

4) next up was the BAC valve. you can learn how to do this simple adjustment from the FSM. so i adjusted this and got the idle at a PERFECT rpm. i was SO happy . at this point there was maybe a misfire every minute or so, really nothing big. IDLE fixed!

problem is, after some driving i checked the ohms and the were off a little, dropping by about 200 ohms. i readjusted it, but after awhile of driving i think it goes a little bit off again. is the TPS sensor itself bad possibly?

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okay, so as to not **** off the people that already know what a proper tune up can do, i have a question on TIMING:

so i went to adjust the timing after this. i should have done this BEFORE doing the idle adjustment, but whatever. oh yeah, read the FSM again for this adjustment, or (even better i found) do a search. anyways, the first thing i noticed was, where in hell are these supposed marks on the pulley . i realized that a 14+ year old car will no longer have little dashes of paint left on some pulley in the engine. so i looked hard, did some careful engine turn over, and finally found what i thought were two little grooves. so i took some tremclad and sprayed it on a flathead screwdriver to apply on pulley, with put two different colours, one on each groove. i was using a crappy timing light, with nothing on it except the light and the plug wire clamp. so i proceeded to adjust the timing. i think i may have thought the left groove (looking from the front) was leading, all i know is that it was WAAAY off from the timing pin. i adjusted the CAS until it was centred on the pin. holy crap, my idle is at 100 RPM . i checked the trailing and it was way the hell off, but i just left it. after that i went through the idle adjustment procedure mentioned at the beginning of this post, and got my idle to the right speed again. so,

A) i used the wrong mark on the pulley, right?

B) what the hell does 5 degrees ATDC and 20 degrees ATDC mean? does this have ANY significance it adjusting the timing, considering all we want to do is line up the mark with the pin?

C) what will bad timing do? the engine seems to run smooth but i notice less power down low...

D) general comments?

Ronac

You can adjust the BAC valve?

eViLRotor

iTrader: (2)

A) Yes, sounds like you used the trailing mark to adjust lead spark timing.

B) ATDC = After Top Dead Center
BTDC = Before Top Dead Center
TDC = Top Dead Center

Basically, this is the relationship between spark timing and the orientation of the rotor face. The more you 'advance' your timing, ie BTDC, the earlier your spark.

This generally creates more power within reason.

C) If have too much timing 'retard', too much ATDC, then you will certainly lose power especially at midrange and up. It may also cause incomplete combustion, fouled plugs, poor gas mileage etc.

Factory spec idle timing is 5ATDC. Any more retard than that, I can see your idle dropping due to the fact that the spark timing is too late. The spark (alone with combustion) is what moves the rotor after all.

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So, you need to get the car idling at 750 rpm again, then reset your timing using the proper marks

coldfire

iTrader: (1)

okay thanks for the info evil.
i will also be doing the timing over again...although i'm scared to mess with it, my car is running at a DEAD SMOOTH idle...