New engine warm start issues. Smells very lean
 

New engine wont start warm,, Speeds up but wont catch. If i retard the timing i can get it to catch. but then i need to change the timing back to normal. Running very lean it seems. not sure why. I unplugged the BAC, checked for vac leaks. when i hit the gas when its running sometimes it idles to far down and wont recover. i adjusted the Tps back and forth. Im not sure if its normal for a new engine. But i never had an engine run lean when running like this before. its an 88gxl stock ecu Not sure how to richen it up, the idle rich screw just gos around and around.. Any ideas TY

Time to get a multimeter and start checking things. First, since you've moved the TPS, you need to verify it's set at 1.000v at idle warm. Are you setting the timing properly by verifying the idle speed, then jumpering the initial set coupler, and then adjusting the timing?

Next, I'd bust out the voltmeter and start checking voltages at the back of the ECU connectors. Items such as the AFM, coolant temp sensor, pressure sensor, etc. In the fuel/emissions section of the FSM, you'll find a chart with all the appropriate voltages for which pin. Also, verify the idle mixture screw is still good by doing a resistance check on it.

Engine performance diagnostics on pre-OBD cars is a bitch.

The issue I ran into after an engine rebuild was with my coolant thermosensor (the engine coolant temp sensor). It wasn't the sensor, it was the wiring. You couldn't tell by looking at it. The pins were pulled out of the back of the connector just enough to prevent it from making contact with the sensor.

Well i will start with the tps with the volt meter then, i will hit the idle adjust screw. Im just not good at the ecu pin thingy. I hate that stuff.. But i will give it a try. i gotta start somewhere. Thank you

TPS is 1.00ohm or v at idle The timing is good. Ran fine. till it warms up.. and BOOM. it acts up agian.

The Water Thermosensor should read close to a .5 volts w/key to on and the engine fully warmed. This signal is read at the ECU at pin 2I which is a Green/White wire. Pin 2I is found in the second largest ECU plug, top row, middle pin. Use either of the front mounting bolts of the ECU for the multimeter ground.

The Idle Adjust Screw is on top of the throttle body. The Variable Resistor is the screw by the Pressure Sensor that adjusts the rich/lean mixture and when you play with this screw the engine needs to be fully warmed and the Initial Set Coupler jumpered. Neither screw should turn endlessly. The coupler also needs to be jumpered when the Idle Adjustment Screw is played with. And when the BAC is disconnected you're removing one of the items that stabilizes the idle to 750 rpm when load is encountered by the engine.

I was looking for the FSM with the Pin codes i cant find them. can you help. Thanks Ill check those pins

TPS is 1.000 volts fully warmed up at pin 2G, which is just to the right of pin 2I. I don't know what color it is.

The way you do pinout checks is by taking the black lead an putting it on one of the bolts at the ecu like Satch said. Then, with the key on, ecu still plugged in, stick the red lead in the back of the connector to touch the terminal for the appropriate wire. Read the voltage. Resistance checks are NOT good indicators of whether components are good or not. For instance, you can do resistance checks on components, and they can even fall out of spec, but still be good. Voltage checks are accurate. There's no substitute.

(Keep in mind though, the idle mixture screw is a variable resistor, so checking resistance on a resistor is just how you check it. Checking resistance on an item like a crank angle sensor is not an appropriate way of testing)

http://www.rotaryheads.com/PDF/2nd_g...systems_na.pdf

This is going to be your friend from now on. I'd print it out to have a paper copy nearby.
Pages 4a-30 through 4a-32 is really, really good info.

Ok i will be checking voltages with key on. Should i wait till car is cold. do the checks. then warm it up and check the pinouts agian?

Some pins can be read when cold and some not. The Water Thermosensor is .5 volts warm and 2 to 3 volts cold. The TPS must be read w/the engine fully warmed up and the engine running or immediately after it is turned off after it has been fully warmed up.

what the hell is the TPS Reading off of that makes the Ohms go UP as the car cools down?

Tps reads 5 plus when warm. Cant even get it down to 1. Unless its full out Plunger can that make it run lean?

The Thermowax causes the primary plates to open up as the engine cools which moves the throttle linkage which rests upon the TPS plunger. This why you cannot set the TPS until the engine is completely warmed up.

Are you certain you're measuring the right ECU pin? And are you by chance confusing the TPS w/the Water Thermosensor? Pin 2G (Green/Red wire) is the TPS for an S4 and pin 2I (Green/White) is the Water Thermosensor for an S4. Do not ohm out the ECU w/key to on! (this can cause damage) You test for voltage only.

Well... I really don't think that could make it run lean, but surge like hell though. You say you can't get the reading down below 5 volts fully warm, unless the plunger is fully extended? The plunger should be almost completely collapsed with the throttle shut. Does adjusting it make ANY difference?

switched out tps. same problem. still looking

to it was tps. I changed it. same problem. i changed out MAS air flow sensor too

Please, for the life of Brian, tell us which wire you are measuring that states the TPS is at 5 volts and the location of that wire.

Took me awhile but i got some Numbers off the ECU.. Some pop out at me. and dont look right. Such as Pin 2i. But here it is. let me know what you think..
Car cold. not bone cold. KEY ON
N327 EGI computer

2a 4.97 V V ref ?
2b 0 no turbo.
2c o ground
2d 0 02sensor
2e 4.02v air flow meter
2f 4.97 v ver Resistor
2g 1.79v throttle sensor
2h 4.02v pressure sensor
2i 4.96v ??? water thermal sensor
2j 2.61v intake air temp
2k 0 Split air Soliniod
2l 3.74 v another intake air sensor
2m 0.73v pressure soliniod valve not sure what this is
2n 11.26v car off key on EGR
2o 11.26v car off key on switch solenoid valve
2p 0 volts ? relefe soleniod valve
2q 1.35 v Bypass air
2r Ground. 0.001

anything strange here? here is the link to what they should read..
http://imgur.com/iVQlO

I did the wrong two. the correct reading was Green and orange on the tps

Change pin 2i to 2.05v. i Unplugged it thinking it would ix the problem forgot to plug it in

Well. I got it to idle warm.. pretty good.. I am just going to guess that the new apex seals Need to seat. I just dont have a farking clue. Cause it wont start warm.. it will Roll start warm. thats about it. My rebuild Before this one didnt do this

NM. I got it started. rolled it out of the Garage at 2 am. drove it hard for an hour. I think its working.

Your water thermosensor is a smoking gun. 4.96v? Even with the engine cold, it should not read near 5v. You have an open wire somewhere. Unplug the water thermosensor and see if the pins are making contact. You may need to pull the alternator off to get to it. It's located right behind the thermostat housing.

Good luck! I think you're almost there :)

And properly adjust your tps!