silverrotor

iTrader: (1)

Been going on for the last 3 weeks. When started I go through my usual 1500 rpm start up. After warm up the car Idles at 500 rpm with the Interest of shutting off on me. It is not until the car fully warms up that my Idle goes to the sweet 750rpm that I'm used to.

On the 88'GXL, I have checked all vacuum conn., TPS, and codes non to my avail. that looks out of place.
Suspected It was the Crane Cams Ignition Box b'c It had died on me in less than a year when Installed, but wasn't It.

I also suspected the TPS aswell. I set It after fully warming up than say, 2 days later I check to see If the one light stays let and sure enough It will have both lights lit or sometimes NONE will be lit. I know what you may be thinking- I'm not pressing the screw down hard and turning It at the sae time like a neandrathal

NZConvertible

Sounds like your thermowax may have failed, and is not opening the throttles to increase idle speed when the engine’s cold.

silverrotor

iTrader: (1)

Thats a possibility. In warmer eather, like today, the Idle wasn't that bad. Whats the advantages/disadvantages of removing this from the TB. What do you think I should do, If It Is iIn fact the thermowax?

silverrotor

iTrader: (1)

Also, could the Thermowax explain why the test lights vary everytime I check the TPS?

darkwaveboi

do a search on TB mod. agreed disadvantage mostly includes heel-toeing to keep idle up during cold engine stages.

HAILERS

SILVERROTOR////////The thermowax, when the car is cold, holds the primary throttle plate open approx .016 or thereabouts i.e. the throttle is cracked open a bit. As the car warms up, the piston on the thermowax extends and pushes against a screw which drives a simple cam until the cam falls off a roll pin. When that happens the .016 gap closes and you are now dependent on how well you set your idle when you did set your idle at sometime or other. But the answer as to why the tps is effected is that the thermowax when cold, causes the throttle lever to move. Throttle lever moving causes the reading of the tps to change. The plunger moves. When the cam mentioned above falls off the roll pin the throttle is back to full warm and the tps now reads correct. Correct reading IF you set your tps with the car fully heated up. Lot of gibberish here. Its five thirty and time to go to WORK! EDIT: Best thing a fellow can do is pull his throttle body off and stare at the thermowax, fast idle cam and screw and primary throttle gap as he pours a quart of boiling water over his thermowax. You can see the relationship of the above items as the thermowax extends and retreats.

silverrotor

iTrader: (1)

Thanks HAILERS for the description of the Thermowax! I will take out the TB and look for the thermowax. What does It look like? Your not talking about the Waterthermo Valve that run coolant to It? (2 for manual. 3 coolant lines for automatic).

HAILERS

Nope, Silverrotor. I'm attaching a jpg out of a 87 manual. The thermovalve is an item used for the double throttle diaphram. The thermowax is for fast idle during startup and is on the back of the throttle body just like the thermovalve is. You really have to take the throttle body off to get a good look at it and adjust it. Normally it should need no adjustment unless someone has messed with the fast idle screw and thermowax screws. Here's a jpg :

silverrotor

iTrader: (1)

So It may not need to be replaced, just adjusted you say? But, It wasn't tampered with. Maybe, By looking at It, I can better understand the Thermo Wax and Its operation!

HAILERS

I re-read the original post(a unique procedure for me) and, hey thats not happening right. You have a 88N/A. You should get an approx 3000rpms on start up for seventeens seconds, then the car should idle around 1100 and gradually drop down to 750 rpm. You say the tps adjustment is not holding. HMMMMMM. Set fully warm and checked a couple of day later fully warmed up and its off. HMMMMMM. Could be the thermowax isn't responding right. Thermowax is the reason they say the car has to be fully warm (hot) when setting the tps. The thermowax shouldn't be a player after the car is fully hot. The thermowax when in aciton, MOVES the throttle linkage to crack the primary throttle plate open approx .016 or so. Anything that moves the throttle linkage, moves the plunger on the tps. Move the plunger on the tps, and the setting of the tps is thrown off. Of course the throttle linkage is moved by your foot, thats natural and allowed. The linkage is move by the thermowax when the car is cold until the car is warmed up, that is allowed. But when the thermowax is fully warmed up, it should not be moving the linkage anymore. The .016 gap should not be there anymore after the thermowax has fallen off the cam, or is that the cam has fallen off the roll pin. Sorta chicken egg thing. What causes the car to go to 3000 is the ECU sensing that the water themp switch, located on the bottom of the radiator, left side, is sensing a cold water condition. It does this by the water temp switch at the bottom of the radiator making a circuit b/t the two bullet connectors that are attached to it. Are both these bullet connectors connected to the water temp switch at the bottom left of the radiator in place? Write back. OR, if they are in place, get a piece of bare wire, pull the bullet connectors off, and insert the bare wire b/t the two bullet connectors. Don't let the wire touch anything else. Start the car. The car should go to 3000 for 17 seconds. Write back. This is just the beginning. Gives a clue to what is going on here. Also, do you have a volt meter and know how to use it to some degree? It would help. I'm just an amatuer myself at it.

HAILERS

Just another note here. The 3000 rpm is caused by the ECU sensing a complete circuit b/t the two bullet connectors at the water temp switch at the radiator. When it sees this, it kicks the BAC into play along with the Air Bypass Solenoid for the time of seventeen seconds. They are the players that make the high rpm happen. So, if your car is fully warmed up and idling at the 750 rpm, if you take the electrical plug off the bac, does your idle respond by dropping down a touch????

silverrotor

iTrader: (1)

Thanks HAILERS for really taking the time to findout "What The Hell Is Up With My Idle"?

I have made every effort to set and check the TPS when It Is FULLY warm. In the matter of the cooling system, I have, over the Winter, replaced Water Temp. Switch at the Rad (yes, It Is connected), Coolant Level Sensor (at the top of rad), Coolant Sender Unit (left side of engine mount and I bought the Coolant Temp Sensor (behind water pump) but will replace when I change Oil Metering Lines. I consider It VERY imp. to take the Cooling System seriously eitherwise you will end up with a COOKED engine FAST!
As far as start up, I don't get the 3000rpms I hear about. I ALWAYS get 1500- exact, than the usual 750rpm.
I do have a Volt meter with a basic understanding. When BAC Valve is unplugged, my Idle tends to drop. Iam convinced the Thermowax is the culprit and It must be fixed. Also, I have checked the resistance of the BAC and the AWS and both are within specs.

HAILERS

Darn the bad luck! Those parts you replaced cost a bundle. You're serious about fixing the thing. Hey, it is probably thermowax related, but try this little method for the tps. Warm the car up fully. Do not shut the motor off. Find a good ground for your meter. Now find the tps connector. Not that green thing, but the tps connector. Put your positive lead in the back of the green wire with the red stripe. Do not disconnect the tps plug at anytime when doing this. Positive lead in the back of the green wire with the red stripe. If the engine is fully warmed up, the meter when put on DC volts, should read ONE VOLT ( 1 VOLT). If it does not, turn the tps screw until the meter reads one volt on the nose. Exercise the throttle a few times and recheck. It might vary from one volt to say .95volt or 1.05 volt, and that is acceptable. Drive around the block and repeat checking the voltage at the green wire with the red stripe. After a day or so of driving, check it again and see how close it is. I do this setting with the engine idling. I KNOW that the manual, when using the lite method says to have just the key to on. And that is true if using the two light method. Not required if using a meter to look for one volt at idle with a hot engine. If you use the lites with the engine at idle, the setting will be screwed up. I forget how I determined that. Sorry. I have used both the light method and the meter looking for one volt method. Both work fine. Darn if I can figure the three grand not working at cold startup.Yet.

HAILERS

I just thought of something else that keeps the three grand cold idle from happening. There is a neutral switch on the transmission. Its job in life is to send a ground signal to the ECU when the car is in neutral. No ground signal results in no 3000 cold idle for seventeen seconds. You can check this wire at the ECU with a meter and putting the car in and out of neutral. One thing I noticed, is that if the ground signal is missing, the idle loses a hundred or so rpm. Might be worth your while. Takes but minutes to check.

silverrotor

iTrader: (1)

You know, It Is really Interesting you mention the Neutral Switch an It's connection. When I purchased my FC, 3years ago, (private deal- Go Figure) I had found a plug dis-connected to the right of the tranny. It prevented my reverse lights to light up. I don't know If this connection Is relevant or not. I noticed It when I as getting the ride to pass safety.

Why was the effort used to keep this disconnected- I dont know!

As far as the Cooling Sensors go, It cost me, with taxes and a 20% discount, under $200 can. Strangely enough I will be Installing my Flex-A-Lite Black Magic Electric Fan #150 this long weekend. I posted a question on related wiring elsewhere In this forum. I will check the Neutral Switch again aswell as the Thermowax.

HAILERS

Neutral switch is on the right side of the transmission. You can monitor the signal at the ECU's largest plug, the one to the far rigtht on the ECU. Its pin 1G. Its a green/black wire. You count the pins with the plug connected to the ECU, looking from the back of the plug into the ECU. 1A will be the top far right pin. 1B will be just below it. 1C will be the second pin on the top row counting from the far right and on and on. In other words count from right to left going up and down until you reach the last one on the left. You can access the signal for the neutral sw by pulling the plug off and ohming the the forth pin over on the top row counting from the right to left. Put the stick in and out of neutral. I have switch in my turbo that gives on occasion a high reading and causes the start up of the engine to languish at 1000 or so rpm instead of the higher rpm. Also messes with the fuel mixture at idle.

silverrotor

iTrader: (1)

Well that Is something to consider next time I pull out my ECU. I have resoldered all electrical units In my FC except the ECU. I will check out the signal at the ECU and check out Its relation to the Neutral Switch.

Then again, with the type of exhaust I am running (RB Header. S.S Catback System-Brullen and a high flow cat) I may opt to keep what I have (the non 3000rpm start up). I mean, I'll be setting off car alarms everytime I start my car- very loud!

I will check out the Thermowax and hopefully cease this problem.