Another code 33
05-10-2010, 10:28 PM
#1
Junior Member
Thread Starter
Join Date: Mar 2010
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1988 Camaro IROC-Z
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: 2.77
Another code 33
Alright guys, I know this is a constant problem after searching the site but I'm out of ideas. I'm going to try and outline my problem the best I can.
I have a 1988 IROC with a 350 TPI. I bought the car back in October and it ran good. Drove it about 130 miles home with no problems. I was getting an SES light, took it to a mechanic I know and he scanned the comp and said it was a MAF problem. Engine still ran good. I decided to replace the MAF with a rebuilt one from autozone. That one lasted about 2 weeks before the the car started running very bad. MAF is guaranteed for a year so I got another one. Again lasted a few weeks ran before problems started again. This time I got a code 36, MAF burnoff. Replaced the relay, helped, but still problems and code 33. Replaced MAF again and again a few weeks and it did the same thing.
I can start it up, idle is fine, take it out and she will run fine then all of a sudden rpm's will drop out and almost no power and the engine will make a metal popping sound when trying to give gas. Let off for a second or two then gas it she will run around 3000-3500 just to do 40. SES will light, then after a few minutes of this the power will return like there is no problem.
I've taking it to the Chevy dealership in town, they scanned the computer finding no errors in the programming or PROMS, fuel pressure is fine. I found a code 33 flow chart on here, checked MAF wiring with test light and volt meter at my house and this lead me to MAF being faulty. I cleaned the connections on both the MAF and MAF connector.
I ordered a new MAF from hawksthirdgenparts.com but before installing this one, is there anything that could be burning the others out? What are your opinions on the cause of this?
Things I've done to the car since I bought it. About 4 MAF sensors, K&N air filters, Accel spark plugs, new MAF burnoff relay, new MAF burnoff relay connector, Royal purple oil, K&N oil filter, and rear hatch supports. Car already had a hypertech chip when I bought it.
I have a 1988 IROC with a 350 TPI. I bought the car back in October and it ran good. Drove it about 130 miles home with no problems. I was getting an SES light, took it to a mechanic I know and he scanned the comp and said it was a MAF problem. Engine still ran good. I decided to replace the MAF with a rebuilt one from autozone. That one lasted about 2 weeks before the the car started running very bad. MAF is guaranteed for a year so I got another one. Again lasted a few weeks ran before problems started again. This time I got a code 36, MAF burnoff. Replaced the relay, helped, but still problems and code 33. Replaced MAF again and again a few weeks and it did the same thing.
I can start it up, idle is fine, take it out and she will run fine then all of a sudden rpm's will drop out and almost no power and the engine will make a metal popping sound when trying to give gas. Let off for a second or two then gas it she will run around 3000-3500 just to do 40. SES will light, then after a few minutes of this the power will return like there is no problem.
I've taking it to the Chevy dealership in town, they scanned the computer finding no errors in the programming or PROMS, fuel pressure is fine. I found a code 33 flow chart on here, checked MAF wiring with test light and volt meter at my house and this lead me to MAF being faulty. I cleaned the connections on both the MAF and MAF connector.
I ordered a new MAF from hawksthirdgenparts.com but before installing this one, is there anything that could be burning the others out? What are your opinions on the cause of this?
Things I've done to the car since I bought it. About 4 MAF sensors, K&N air filters, Accel spark plugs, new MAF burnoff relay, new MAF burnoff relay connector, Royal purple oil, K&N oil filter, and rear hatch supports. Car already had a hypertech chip when I bought it.
05-16-2010, 01:26 PM
#2
Re: Another code 33
Welcome Aboard!
Code 33 MAF Tests
The MAF is a sinking input device. In other words, the ECM supplies a current-limited 5VDC supply to the MAF sensor, and the MAF will ground that signal down closer to 0VDC at lower than maximum detected air flows. If the logic circuit ground connection to the MAF is not continuous, or is not properly grounded, the MAF cannot pull down the 5V signal as it is designed to do. Thus, the MAF ground must be at the same potential as the ECM ground - The system MUST have good grounds everywhere. Similarly, if the MAF signal circuit suffers from poor connection or continuity, the signal may be higher than intended. All wiring and connections must be intact.
The MAF burnoff system can also cause this code to set if the MAF burn off relay or circuit has problems with resistive leakage, bridging connections from corrosion, poor grounding, etcetera.
You really don't need anything more than a good volt/ohm meter to diagnose the system. With the ignition ON and engine not running, make sure the correct voltage and grounds are present at the MAF terminals.
Test the MAF Signal Voltages
Diagnosis
A code 33 is set when the ECM has detected an intake air flow above 45 grams per second (about 2.2 volts) for one second when the engine is first started or at any time when the TPS is less than 1/4 throttle and RPM is less than 2,000.
If you discover problems in the voltage or grounding checks, re-seat the connectors at the ECM and check all the circuit grounds. Make sure the connector at the MAF itself is intact.
If there is a problem with the 5VDC reference voltage from the ECM, re-seat the ECM connectors and/or test for the correct voltage directly at the ECM terminal B12. If there is not 5VDC source (± 0.6V) present at the ECM connector, the ECM itself may have a problem.
With the ECM connectors clean and properly connected, if the reference voltage is significantly higher than 5VDC, there may be a problem with the other wiring shorting to that circuit on the vehicle.
If you are able to read voltage at the MAF burnoff circuit, remove the MAF burnoff relay and retest. You can even run the car in this mode, but will eventually set a "36" code for the burnoff failure.
If all voltages are correct, and all grounds and connections are intact, the MAF itself may have problems. A MAF failure causing a "33" is uncommon, but I suppose it is possible. It is generally more common to find circuit problems or a TPS adjusted too low.
Connecting a 12VDC power source to the fuel pump test terminal ("G" terminal of ALDL) will provide power to the MAF sensor, and the MAF signal circuit should create a low voltage (less than 250 mV) signal to the ECM. Monitoring the MAF signal voltage in this mode and wiggling the circuit connectors and wiring may allow you to detect any intermittent problems. Similarly, an erratic MAF signal with the engine running may indicate wiring or connector problems.
If you determine the MAF has a problem, the MicroTech 491018 units are decent replacements. They are identical to the old Wells SU-145 units.
Code 33 MAF Tests
The MAF is a sinking input device. In other words, the ECM supplies a current-limited 5VDC supply to the MAF sensor, and the MAF will ground that signal down closer to 0VDC at lower than maximum detected air flows. If the logic circuit ground connection to the MAF is not continuous, or is not properly grounded, the MAF cannot pull down the 5V signal as it is designed to do. Thus, the MAF ground must be at the same potential as the ECM ground - The system MUST have good grounds everywhere. Similarly, if the MAF signal circuit suffers from poor connection or continuity, the signal may be higher than intended. All wiring and connections must be intact.
The MAF burnoff system can also cause this code to set if the MAF burn off relay or circuit has problems with resistive leakage, bridging connections from corrosion, poor grounding, etcetera.
You really don't need anything more than a good volt/ohm meter to diagnose the system. With the ignition ON and engine not running, make sure the correct voltage and grounds are present at the MAF terminals.
Test the MAF Signal Voltages
- The MAF signal circuit (Terminal C) should be less than 0.3V with the ignition on and engine not running.
- Disconnect the MAF electrical connector and test the voltage again. There should be a 5VDC reference voltage from the ECM.
- Verify that the TPS voltage is between 0.47 and 0.61VDC.
- Test for voltage in the MAF burn off circuit (Terminal D at the MAF) while the ignition is on, engine off or running. Any voltage present can cause the MAF signal at the ECM to be too high.
Diagnosis
A code 33 is set when the ECM has detected an intake air flow above 45 grams per second (about 2.2 volts) for one second when the engine is first started or at any time when the TPS is less than 1/4 throttle and RPM is less than 2,000.
If you discover problems in the voltage or grounding checks, re-seat the connectors at the ECM and check all the circuit grounds. Make sure the connector at the MAF itself is intact.
If there is a problem with the 5VDC reference voltage from the ECM, re-seat the ECM connectors and/or test for the correct voltage directly at the ECM terminal B12. If there is not 5VDC source (± 0.6V) present at the ECM connector, the ECM itself may have a problem.
With the ECM connectors clean and properly connected, if the reference voltage is significantly higher than 5VDC, there may be a problem with the other wiring shorting to that circuit on the vehicle.
If you are able to read voltage at the MAF burnoff circuit, remove the MAF burnoff relay and retest. You can even run the car in this mode, but will eventually set a "36" code for the burnoff failure.
If all voltages are correct, and all grounds and connections are intact, the MAF itself may have problems. A MAF failure causing a "33" is uncommon, but I suppose it is possible. It is generally more common to find circuit problems or a TPS adjusted too low.
Connecting a 12VDC power source to the fuel pump test terminal ("G" terminal of ALDL) will provide power to the MAF sensor, and the MAF signal circuit should create a low voltage (less than 250 mV) signal to the ECM. Monitoring the MAF signal voltage in this mode and wiggling the circuit connectors and wiring may allow you to detect any intermittent problems. Similarly, an erratic MAF signal with the engine running may indicate wiring or connector problems.
If you determine the MAF has a problem, the MicroTech 491018 units are decent replacements. They are identical to the old Wells SU-145 units.
06-06-2010, 09:08 PM
#3
Junior Member
Thread Starter
Join Date: Mar 2010
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1988 Camaro IROC-Z
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: 2.77
Re: Another code 33
Thanks Vader!
Well, I have good news and bad news.
I went and bought a micro-tech maf sensor which helped the driveability but still having problems.
checked out voltages and such this is what I found:
1. Reset TPS voltage. Was .70 now ~.54 to .55
2. MAF voltage ignition on, engine not running is .07
3. MAF voltage engine running with what I would call a drivable idle is .88 engine still "surges" bouncing off 500rpm to about 650rpm before droping back and repeating. This is with trans in Drive (D) sitting. Trans in Neutral (N) engine is running about 600rpm.
When the engine is "surging" MAF voltage at Term C is .9 up to 1.25
4. No voltage in MAF burnoff relay, Term D. Speaking of which, I have a few picks, can anyone tell me what relay is the burnoff? I unplugged each of the individually (staring next to engine and working to fender, one unplugged and 2 connected) and the car started each time. Only the middle relay threw a code. Didn't check to see what it was.
Removed the computer and found out it was a rebuilt one. Knew about the hypertech chip but there is what looks like melted glue on the circuit board. Pick also included. Sorry about the quality, they are from my phone.
Relays
Computer with hypertech
Computer glue
Computer rebuilt sticker
Whole Engine
Well, I have good news and bad news.
I went and bought a micro-tech maf sensor which helped the driveability but still having problems.
checked out voltages and such this is what I found:
1. Reset TPS voltage. Was .70 now ~.54 to .55
2. MAF voltage ignition on, engine not running is .07
3. MAF voltage engine running with what I would call a drivable idle is .88 engine still "surges" bouncing off 500rpm to about 650rpm before droping back and repeating. This is with trans in Drive (D) sitting. Trans in Neutral (N) engine is running about 600rpm.
When the engine is "surging" MAF voltage at Term C is .9 up to 1.25
4. No voltage in MAF burnoff relay, Term D. Speaking of which, I have a few picks, can anyone tell me what relay is the burnoff? I unplugged each of the individually (staring next to engine and working to fender, one unplugged and 2 connected) and the car started each time. Only the middle relay threw a code. Didn't check to see what it was.
Removed the computer and found out it was a rebuilt one. Knew about the hypertech chip but there is what looks like melted glue on the circuit board. Pick also included. Sorry about the quality, they are from my phone.
Relays
Computer with hypertech
Computer glue
Computer rebuilt sticker
Whole Engine
06-09-2010, 05:47 PM
#4
Junior Member
Thread Starter
Join Date: Mar 2010
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1988 Camaro IROC-Z
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: 2.77
Re: Another code 33
Update:
Checked out all the ground wires that I could find with a continuity tester, everything was fine. Also tested what I believe to be the ground wire for the MAF sensor (black wire with white stripe that connects to the back drivers side of the engine block. Also fine.
The MAF burnoff relay I replaced (along with the connector) was part #10094701 the first next to the engine. I figured the car would not start or keep running with the fuel pump relay disconnected but at one point that relay was unplugged and ran fine. So which relay is which?
Car is idling a little better but still problems. Starting is fine, idle ok. Putting in in gear is ok, hitting the gas to pull out into traffic the car almost dies. Let of the gas idle is ok, hit the gas again and there is zero power, engine bogs down horrible. Pumping the gas or holding the pedal down will eventually cause power to return but the car launches forward. SES will light. When the engine eventually gets warm this "mostly" goes away. Computer throws a code 33 still. I have no clue what's going on. Any help would be greatly appreciated!
Checked out all the ground wires that I could find with a continuity tester, everything was fine. Also tested what I believe to be the ground wire for the MAF sensor (black wire with white stripe that connects to the back drivers side of the engine block. Also fine.
The MAF burnoff relay I replaced (along with the connector) was part #10094701 the first next to the engine. I figured the car would not start or keep running with the fuel pump relay disconnected but at one point that relay was unplugged and ran fine. So which relay is which?
Car is idling a little better but still problems. Starting is fine, idle ok. Putting in in gear is ok, hitting the gas to pull out into traffic the car almost dies. Let of the gas idle is ok, hit the gas again and there is zero power, engine bogs down horrible. Pumping the gas or holding the pedal down will eventually cause power to return but the car launches forward. SES will light. When the engine eventually gets warm this "mostly" goes away. Computer throws a code 33 still. I have no clue what's going on. Any help would be greatly appreciated!
Thread
Thread Starter
Forum
Replies
Last Post
