nepopolus

just purchased a 86 gxl,when i first got it the idle was insane and at 3000 rpms, thanks too this fourm got it down too about 1400,tonight i was going too start checking the tps and adjust if needed.Well when i went too start it she died a couple times after running for a few seconds,finally got it too idle, but i noticed the cold start system did not seem too activate(let off gas it would go down too 1000 rpms, when the engine temp needle was still at c) so i basically tried too manually do it and give it a bit of gas too 2000 rpms. After the engine temp needle starting moving i let off and the idle went back too its 1400 rpms. But when i gave it gas too move it into my shop the second the rpms went over 1500 it would studder and drop rpms(while i was still giving it gas), so i figured i would let it idle too normal operating temp, I did but it had the exact same problem as earlier.

I hate too start threads on idle issues with this car seeing as how when i searched them there was a TON, but i did not see any with the issues i am having sorry in advance.

also tps sensor plastic shroud too connect into the wiring harness has a small piece missing(already figured there is a good chance i will need a new one) o2 sensor also seems too have been broken and re soldered back together(i am buying a new one)

thank you all for your time

AGreen

iTrader: (11)

The cold stuttering may me a large number of problems. It could be worn spark plugs, vacuum leak, spark plug wires, corroded connections, a bad or dying airflow meter, etc.

The idle problem is simple. In the FSM under the fuel/emission section, it shows you a picture of the "thermowax". Essentially, all it does is keep a plunger extended until the engine coolant warms up. There is a very small coolant passage inside that has the potential for getting clogged with corrosion. When you first start the car cold, before even cranking it, you're supposed to tap the throttle once. This puts the fast idle cam on the extended plunger, keeping the butterflies open a little.

The thermowax also has, on the back of it, a thermostatically controlled vacuum "switch". It's open when cold, and shuts when hot. It controls vacuum to the "double throttle" vacuum operator. When cold, it will keep the second set of throttle plates shut. Once warm, it'll allow them to open through a delay valve, located underneath the throttle body.

nepopolus

alright thank you i will check it out tomorrow.
edit: the rpm studder with throttle just started tonight. never did it before

nepopolus

update
changed spark plugs and wires(oil leak dripped onto one of them im sure that was great for it)but the misfire is now gone. Turns out the thermowax system was taken off by the previous owner when he did the emissions delete on the car, coolant lines are plugged and where taken off.This wouldn't be too much of a problem for me since it is not my daily, nor do i ever plan on driving it in Chicago winters


now i just have too fix the 1400 rpm idle, idle adjustment screw is already as far as it will go(now it just loses contact with the actual throttle body piece) so i put it back too where it just touches the lever and left it there.Would the BAC valve be the next on the list?

also it has the normal 3500 rpm hesitation i will search the million things too check for this

AGreen

iTrader: (11)

The throttle stop screw should have never been messed with. You're going to need to remove the TB and go through the FSM and figure out how to set it. It gives you values for how far the plates should be kept open by the stop screw. That in mind, the actual idle adjustment is a screw on top of the throttle body. It should be covered by a black cap, but a lot of times previous owners or mechanics will lose it. Try cranking that little guy down. Also, warm the car up fully and adjust the TPS to 1.000v. It'll be the green/red wire on the harness side of the TPS connector.

The BAC can only raise idle, not lower it. Unless it's stuck open, it's not going to idle it up that high. Try unplugging it to see if the idle goes down, but I'll bet you a dollar it won't

If all else fails, resort to the carb spray around the intake manifold area to look for a vacuum leak. The idle will change when you hit the leak with carb spray. Any kind of spray like brake cleaner, carb cleaner, throttle body cleaner, etc. Don't use starting fluid, it's way too volatile. Not saying it won't work, but it's bad ju-ju if it hits anything that can ignite it. The other sprays are flammable too, but not as violently explosive like ether starting fluid.

Once you get the idle down to around 750-ish, verify the timing's right.

AGreen

iTrader: (11)

Edit:
Disregard this attachment. It's not the right clearance. I'll have to look for what I was talking about.

nepopolus

no vac leaks, sprayed carb cleaner on the intake and surrounding area 2 times no change at all,but im almost positive my tps is toast thanks too half the connecter being broken(some corrosion on the connecters from this, i cleaned them the best i could),It seems it is getting a very weak connection, the multimeter is all over the place with the slightest movement in the engine bay so making adjustments was almost impossible... also found out the 5th and 6th port are not engaging thanks too arrons tips on his site. after the drive the idle actually went even farther up too 2000 rpm's. And i owe you a dollar unplugging the BAC valve did nothing

satch

iTrader: (1)

With the car idling, what happens when you press "upward" on the throttle linkage located at the front of the throttle body?

With the BAC unplugged look at the two terminals to the BAC solenoid and place a ground to one terminal and battery voltage to the other terminal and don't place both wires to one terminal by accident. When you place each wire properly to the BAC terminals the device should click. Do this a few times to perhaps unstick the BAC if this were the case.

nepopolus

by pressing up i would assume you mean try and close it more? i can get it too idle perfect if i do that until i give it gas anyway i will go check the BAC test you recommended now

satch

iTrader: (1)

If pressing upwards has the affect of dropping the idle then perhaps you have the throttle cable binding or too tight or perhaps the Fast Idle Cam is not set properly. The BAC is likely not stuck if pressing upwards on the linkage drops the actual idle speed.

Look at the back of the throttle body and locate the throttle linkage that pertains to an upside down screw that lies below the Thermowax which has a metal piston that protrudes from it. Take a rubber cap about an inch in length which is used to plug up a nozzle and place it on top of the upside down screw in an effort to have the top of the cap rest against the Thermowax. In doing so you will be able to bypass the Fast Idle Cam mechanism. Then start the car and observe if the idle lis lowered as compared to previous readings.

nepopolus

alright, omw soon too check, i am going too take a few pics of my throttle body...looking at the fsm this guy took off a lot of stuff...luckily this is my project car. also there are quite a few disconnected plugs and a strange fuel system mod? i guess.....at this point i cant wait too try and fix my rpm hesitation at 3800 haha
also update too satch thermowax was removed by previous owner
and thank you both so much for your time in helping me with this

satch

iTrader: (1)

The hesitation is probably due to a poor ground running to the engine sensors. Pick a sensor like the Pressure Senor and shove a jumper wire into the back of the plug where the ground wire resides and then ground the other end of the jumper wire to the engine such as the thermostat housing and then take the car for a drive to notice a lack of hesitation. If this works then properly solder the end of the jumper wire shoved into the back of the plug to the ground wire itself. The sensor has four wires. W/key to on one wire has 12 volts, another wire has 5 volts, a third wire will have 3.5 to 4 volts and the final wire will have no voltage as this should be your ground wire to work with.

And of the three TPS wires which one is suffering from a bad connection? Black, Brown or Green/Red?