well, after 6+ months of getting the time to actually work on my car, i finally turned the key on it today (first time after about two months ago with the first attempt). fuel pressure wasn't even set, but i turned the key to check battery and crank power, and it decided it wanted to start, so i let it run for a minute or so. anyways, i need to set the fuel pressure, iac, tps, eng rpm, etc., (and set timing) and i need to know in which order i need to do these things (and anything else i may be leaving out). i did get a service engine light, but have not pulled the code(s) off it yet. i know i need to do that, but had to run off today and haven't been able to get back to it. for all it matters, the engine seemed to run really well and stable, so i think i got most of the problems i encountered last time taken care of. thanks for any responses. great to have this board up again.

KAM

 

I would say:

First: set the fuel pressure to 44psi or other if you know better.

Second: do the idle air, but here is where I do it a bit different, I set the idle RPM at 650RPM not the 450RPM as stated in the procedure. This will keep the IAC count lower, this will help stalling when you come to a quick stop.

Third: set the TPS volt at idle to 0.60 to 0.64V, this upper end voltage will improve the throotle response.

Fourth: set the static timing to what works good for your engine and pickup. (remember to disconnect the EST wire).

 

thanks for the response... i have a problem with the TPS voltage, though. it will not go past 4.3. i understand that 4.2 is minimum, but i cannot get it to go past that. IF i rotate the tang on the TPS sensor itself, it will go all the way to 6.8, but if i rotate it by throttle, 4.3 is the best i get. with that being said, on the other end of the spectrum, my idle stop "gaps" before i can actually lower idle any further. in other words, if i try to lower the idle any more, i cannot.

so... what happened today, is that i set TPS to 4.3, set timing, set IAC which threw timing way off (apparently it was wrong) and then reset timing. yes, i disconnected the EST connector. the idle is around 800ish, timing is about 8*. keep in mind i've got an LT4 hotcam w/1.6 rockers ... fuel pressure is set at 42 w/engine running and no vacuum on the regulator. with that combination, engine seems to be running good.

also, i have a hard code 43, which is supposedly something to do with EST voltage low or ESC circuit. i don't know what to do about that... i replaced the computer, but only other thing i know of is the IGNITION module. will this code cause the engine to stall out like if i'm backing up and shifting to drive? stalls out also when going around a corner or pulling in to the driveway (at idle speed).

thanks for any help.

KAM

 

You set the TPS voltage at idle, not for WOT. When I set my idle TPS voltage to 0.62V, I get about 4.3V at WOT. I think that this is typical. Also, I think that if the TPS voltage goes above 4.0V at WOT, things will be OK.

Sometimes, when you adjust the timing (and by doing so disconnected the EST wire) you will set an error code. So after reconnecting the EST wire, simply disconnect the ground terminal at the battery for 2 minutes, to clear all error codes.

I dont know what to say abouit your stalling issue.

 

Or you can try this:

Throttle Minimum Air Position

Tools needed:
1. Torx driver # T-20
2. Paper Clip
3. Small Punch
4. Tachometer

GENERAL NOTE: The engine should be at normal operating temperature before performing any adjustments. Never rely on the dash mounted instruments for diagnostics and adjustments. The oil pressure and temperature gauges and the voltmeter and tachometer just aren't calibrated accurately enough for diagnosis, but are a relative indication for monitoring the vehicle while driving.

For this adjustment, the transmission will be in DRIVE while you're under the hood. You will need to securely set the parking brake and block the drive wheels. It would also be a good idea to have an assistant hold the service brake while you perform the adjustments.

In order to successfully complete the adjustment, the IAC air passages and pintle need to be clean. The throttle plates and bores need to be clean as well. If this is not the case, you'll need to remove the air cleaner from TBI engines or the intake air bellows from TPI engines to gain access to the area to be cleaned. A spray-type carburetor cleaner works well for this. Cleaning the IAC passages on a TPI/MAF engine will set a DTC, but we'll be clearing that later. With the engine idling, direct the spray cleaner in to the IAC air passages and around the throttle plates. Shut off the engine and continue cleaning the throttle plates by opening the throttle manually. Once everything is satisfactorily cleaned, replace the air bellows on TPI engines. Many times, this alone can solve IAC/idle speed problems.

If this doesn't solve the problem, you may need to remove and clean the IAC stepper motor. If the IAC appears to be clean and functioning properly, continue with the adjustment procedure.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Idle Air Control Cleaning

You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.

You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.

When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.

While the IAC is out, clean the air passages in the throttle body. The orifice in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.

When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Locate the ALDL connector under the dash panel, in the driver's foot well area. Remove the plastic trim cover (if it is still there).



Cut and form a paper clip into a "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' sockets.



Turn on the ignition, but don't start the engine. This will force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. Under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector if your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.

Locate the Torx screw on the left side of the throttle body. It may be equipped with a protective metal cap from the factory. This was intended to discourage adjustment. If the cap is present, use a small punch to knock it out. Once the screw is accessible, start the engine and place the transmission in DRIVE. Adjust the throttle stop to obtain 400 RPM with the transmission in "DRIVE" on an automatic transmission car, 450 in neutral on a manual transmission car, rotating the Torx screw clockwise to raise speed and counter-clockwise to lower speed. Once the idle RPM is set, place the transmission in PARK and turn off the engine.

Re-connect the electrical connector onto the IAC. Start engine. Idle speed should be governed by the ECM at approximately 600-650 rpm in "DRIVE" (for unmodified cars). Idle speed in NEUTRAL or PARK is less significant, and will be higher.



Throttle Position Sensor (TPS)

Tools needed:
1. Digital Volt-Ohm-Meter (VOM)
2. Breakout jumper wires or probes (make your own)
3. AutoXray, Diacom, or similar scanner will replace the VOM and jumper wires.

Turn on ignition, but don't start the engine.

With a diagnostic scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.07 VDC.

Connect the VOM to the TPS electrical connector terminals ‘A' and ‘B'.

With a breakout jumper: Disconnect the electrical connector from the TPS. Install the breakout in-line, between the TPS and wiring harness connector. Connect the meter probes to terminals 'A' and 'B' on the connector. (‘B' is the positive connection, ‘A' the signal ground, or negative.)

With probes: If you have very slender probes on your VOM, you can back-probe the TPS connector while it is attached to the TPS. If you have made probes of large dressmakers pins or a similar item, you can back-probe the connector as well. Connect the meter probes to terminals 'A' and 'B' on the connector.

Turn on the ignition to read the TPS output voltage at the idle position. The reading should be 0.54VDC +/- 0.07VDC. The ideal is the center of the range, 0.54VDC for a stock engine. To adjust the output voltage, loosen the two Torx screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, the TPS sensor may be failing and could be a cause of stumbling and driveability problems.

After achieving the desired setting, turn off the ignition switch. Remove all jumpers or the scanner and reconnect the TPS connector as required.

Reinitializing the ECM

If you set a DTC during the procedure, the SES light should be illuminated on the dash. This ECM retains DTC data for the previous 50 engine starts, so the codes will eventually be cleared. If you want more immediate results, after shutting down the engine disconnect the negative battery terminal for five minutes. This will clear the ECM of all diagnostic trouble codes. Clearing the ECM also clears any data learned about your engine, and clears the radio presets. If you have a Delco-Loc or Theft Loc II radio, make sure you follow the procedure to unlock the radio protection before disconnecting the battery. This five minutes is also just about long enough to clean both battery cables. Reconnect the battery. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur within the first twenty minutes of Closed Loop operation.

 

Vader: you have been very busy tonite. The above is a GREAT post!

Tuning tip: You set the fuel pressure for the correct AFR at WOT, not for idle or driving around. The ECM will correct the AFR to about 14.7 when at idle and cruising via the INT and BLM fuel correction factors. So, remember to set the fuel pressure for best WOT performance. (This comment has nothing to do with Vaders post, just a tuning tip on how the ECM works.)

 

sorry to interupt but where is the EST wire for setting timing? is it the 2 pin connector under the plenum?

 

twolfe, the EST wire you need to disconnect is a single tan wire near the blower fan on the passenger side by the firewall. if you follow your hood wire down in to the main bundle, you'll find it right in that area.

doc, thanks for setting me straight on my error with TPS.

vader, thanks for the in-depth article on the IAC and TPS.

hopefully today i can resolve all these and to the exhaust shop monday or tuesday. my car has been down for almost a year...

KAM

 

ThunderStick has it covered, but just to help:

 

Quote:

Originally posted by doc
Tuning tip: You set the fuel pressure for the correct AFR at WOT, not for idle or driving around....

How is AFR at WOT determined? What's your method?