I ran the codes this afternoon after I put the check engine light back in the dash (the last owner must have took it out) and got 33, 34, 36.

All of them are related to the MAF sensor, but the car is running good, other than it will stumble or stall a minute or two after starting it. It usually only does it once then clears up..... Would it be the MAF doing it.....

I just don't want to go and buy one and it not be the problem because they are kinda pricy.....

Thanks
tim

 

You absolutely should not be getting a 33 and 34 simultaneously, unless you have a connection problem at the MAF or a problem with power to the MAF. Check your MAF power and burn-off relays, clear the codes, then try again.

 

I thought that was odd getting both of those codes together...
I have checked the connections, and all looked good..... I cleared the codes a little while ago, but have not checked the codes again.... Took it for a spin around the block and it's is still stalling though....

I will also check the burnoff relay tomorrow.... It is one of the three or four relays on the firewall on the drivers side right?????

 

You might also want to check the voltage and grounds right at the MAF connector:

 

Got it.... That may also explain why my headlights want to go out from time to time.....
Hopefully it is the ground since all my issues seem to be in that general area...

Thanks for the help.
Tim

 

After checking relays I discovered some of the insulation pulled down exposing the bare wire.... I checked the grounds, and voltage at the relays and all looked good, then taped up bare wires....
After clearing the codes and checking again the following day, it came up codes 34 & 36.... I noticed the screens have been removed from the MAF.... Would this have anything to do with it.... Also my temp gauge rarely gets over 180 when driving at highway speeds....

I checked for vacuum leaks and there doesn't appear to be any, but code 34 indicates high vacuum?????

And for code 36, do you think it may be the burnoff relay???? Could I pull out the MAF and turn on the ignition and see if it is in fact burning off??? Will the wire actually glow????

The car runs fine other than the stalling from time to time..... MPG doesn't seem to be that great though.... Smells a little rich at idle as well.....

Idle speed seems a little high as well, but smooth.... When parked it idles a little over 1000rpm's, and when cold even higher up to 2000rpm's....

Tim

 

The 36 is a problem with the MAF burnoff circuit function. The most common problems are a failing relay and poor connections. You can follow this list to help pinpoint the problem:

Code 36 Test

Clear codes.
Start engine.
Ground diagnostics terminal and wait for the check engine light.
Unground terminal.
Shut off car.
Wait a minute or so.
Restart car for 20 seconds or until check engine light comes on.
Shut off car.
Turn ignition to ON position
Check for codes.
No code, problem intermittent.
Code 36, unplug burnoff relay, check both orange wires for power.
If one or both have no power, repair open circuit.
If both orange wires have power, reconnect relay.
Disconnect MAF sensor.
Ground burnoff relay black wire, terminal "F".
Check MAF connector terminal "D" for power.
If no power, replace burn off relay.
If it has power, with relay terminal "F" still grounded, check MAF plug terminal "E".
If no power, replace MAF power relay.
If terminal "E" has power, disconnect burn off relay.
Check burnoff relay black wire (terminal "F") for power. If it has power it is shorted to power somewhere. If it has no power, suspect ECM or ECM connector.
Code 36 can be caused by a bad connection at either relay.
Check relay connector contacts for corrosion and tight fit before replacing ECM.



The 34 can be caused by several problems. The LAST item on the list is a failed MAF sensor. A 34 means that the ECM is getting a lower than expected intake air flow signal at a given engine RPM and throttle position. The ECM calculates and assumes an acceptable range of signals based on RPM and TPS, so it is important to set the TPS voltage to 0.54VDC at idle.

The low signal can also be caused by poor electrical connections at the MAF, MAF relays, or ECM. Make sure the MAF connector is clean and fully seated in the MAF housing connection. Check the connector at the MAF power relay for corrosion, loose wires, and other damage. The relay contacts themselves may be failing and creating resistance, resulting in a lower signal level. You can either replace the relay or measure the resistance of the contacts, or measure voltage drop across the relay in circuit. If all that checks O.K., you may have poor connections at the ECM. Removing and reseating the connectors can help clean them and create a better connection.

Finally, even if everything electrical is in good condition, the MAF can report a lower signal if there are leaks in the duct work between the MAF and throttle body. This can include the bellows, resonator boxes, clamped connections, etc. Any vacuum leak can also lower the amount of intake air being measured by the MAF since it is not flowing through the sensor. These leaks include the EGR, brake booster, hoses, gaskets, and CCV system (which is why you should NEVER use a breather-type oil filler cap on a MAF system).

There have also been cases where a MAF sensor is altered by removing the inlet screens, causing intake air to be diverted around the sampling tube in the sensor body. If you're using a completely stock MAF, this shouldn't be an issue.

 

OK, I changed the two MAF relays and got codes 34 and 36 cleared, now code 33 has came up.... When I start the engine it want to stumble and cut back off, and I have to feather the gas and keep the RPM's up until the SES light comes on....

I have done the searches thru the forum and found some of your old post and pretty much know what to check....

One thing I notice is that the Throttle stop seems to adjusted out quite a bit and in one of your post you state that:

"The TPS is very important in the equation used by the ECM to calculate the expected air flow. The engine RPM signal is also very important. If the TPS voltage is set too low, the ECM will presume the throttle is open less than it truly is, and tend to set the code. The TPS voltage should be
0.47-0.60 VDC at the idle position, with 0.54VDC being the generally accepted standard. You might try to adjust the TPS higher to compensate, but still stay within the specified range. This should tip the ECM toward the correct calculation range.

Of course, this will only work if the minimum throttle position is correctly set. If someone has attempted to adjust the curb idle by moving the throttle position, the ECM may be completely confused and accept a lower TPS voltage than should be reported."


Now my question is what is the specific angle or amount it should be open so I can get the TPS voltage set right?????

Thanks for all the help,
Tim

 

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.

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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.

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Locate the ALDL connector under your dash panel, in the driver's footwell 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 is 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.

 

Or better still, get a TECH 1 like I have and do it a lot easier.
Sorry I had to throw that in. I love my TECH 1.