codes 33 & 36 suddenly won't run - CorvetteForum - Chevrolet Corvette Forum Discussion

Notices
C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

codes 33 & 36 suddenly won't run

Old 12-11-2018, 09:33 AM
  #1  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default codes 33 & 36 suddenly won't run

1986 vert. Yesterday on the way home the car started to stumble a couple times. This morning in the driveway it started fine for about 30 sec and then stumbled and stalled. Would not restart … cranks but no go . Immediately checked the codes with a 33 and 36.

Time to dig in to the FSM

PS: Let it sit 15 minutes and tried to start it again and it started right up but NO CODES this time and no SES????

Last edited by rharker; 12-11-2018 at 10:24 AM.
rharker is online now  
Old 12-11-2018, 11:14 AM
  #2  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 138
Thanked 9 Times in 9 Posts
Default

While it is running, Tap the MAF lightly... don't pound on it, but let it know you are there. If the car stumbles, your MAF is going bad.

Having them both at the same time is interesting.
Code 36 is the MAF Burn off Cycle. This flags when the computer doesn't get the return voltage from the burn off voltage being sent to the MAF. So, either the MAF is faulty, the relay is faulty, or the is a broken wire.

Code 33 happens when the following 3 conditions are true at the same time:
1) engine under 2000 RPM,
2) MAF reading over 45 gms/sec, and
3) less than 25% throttle.

So, either your MAF is bad, TPS is bad, or a power relay is bad.

Do the tap test, test your TPS Voltage (.5-.6V at Idle, <4.5V at WOT) and then check your relays. If all checks out then dig in to the wiring.
KyleF is offline  
The Following User Says Thank You to KyleF For This Useful Post:
rharker (12-11-2018)
Old 12-11-2018, 07:26 PM
  #3  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default

When I got home from work I started it and it started fine ... did the tap test on the MAF and nothing happened. Let it run for a few minutes until it started to act up and then stalled. Checked codes again 33, 36 again. I had a new spare MAF in the box so I swapped it in and tried to start it and it wouldn't so I don't think it's the MAF.

Funny thing was that when I took off the MAF a thick fuel vapor came out of the throttle body if that's any clue.

I guess I'll check the TPS and relays.
rharker is online now  
Old 12-12-2018, 01:11 PM
  #4  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 138
Thanked 9 Times in 9 Posts
Default

Originally Posted by rharker View Post
When I got home from work I started it and it started fine ... did the tap test on the MAF and nothing happened. Let it run for a few minutes until it started to act up and then stalled. Checked codes again … 33, 36 again. I had a new spare MAF in the box so I swapped it in and tried to start it and it wouldn't so I don't think it's the MAF.

Funny thing was that when I took off the MAF a thick fuel vapor came out of the throttle body if that's any clue.

I guess I'll check the TPS and relays.
1) engine under 2000 RPM,
2) MAF reading over 45 gms/sec, and
3) less than 25% throttle.

If your MAF reading is high in Open loop, the car would be adding fuel to compensate. Idle should produce the other 2 conditions. May not be the MAF. If the voltage getting to the unit is low or high... it could affect the output as well.
The relays are like $15 a piece. You can check them, or just swap them.

Was the MAF you installed a hot film or wire style?

The car should start with or without a MAF. Not saying it is going to run well, but it should start/run.

Last edited by KyleF; 12-12-2018 at 01:13 PM.
KyleF is offline  
Old 12-12-2018, 01:30 PM
  #5  
JackDidley
CF Senior Member
 
JackDidley's Avatar
 
Member Since: Sep 2003
Location: Database Error Indiana
Posts: 16,069
Thanked 17 Times in 16 Posts
Default

Every time I had MAF codes, I changed the relays and fixed it. Cheap and easy fix. I will say the car never ran bad, just turned on the service engine light. Three times, I think in 170k miles.
JackDidley is offline  
Old 12-12-2018, 02:56 PM
  #6  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default

Originally Posted by KyleF View Post
1) engine under 2000 RPM,
2) MAF reading over 45 gms/sec, and
3) less than 25% throttle.

If your MAF reading is high in Open loop, the car would be adding fuel to compensate. Idle should produce the other 2 conditions. May not be the MAF. If the voltage getting to the unit is low or high... it could affect the output as well.
The relays are like $15 a piece. You can check them, or just swap them.

Was the MAF you installed a hot film or wire style?

The car should start with or without a MAF. Not saying it is going to run well, but it should start/run.
The original is the wire type MAF and the replacement was a hot film style.

I got the MAF power relay today at lunch and I'll install and test this evening. I don't understand why I'm going through these relays.
rharker is online now  
Old 12-12-2018, 04:15 PM
  #7  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 138
Thanked 9 Times in 9 Posts
Default

Originally Posted by rharker View Post
The original is the wire type MAF and the replacement was a hot film style.

I got the MAF power relay today at lunch and I'll install and test this evening. I don't understand why I'm going through these relays.
Yea, it's almost so cheap to replace the relays it's not worth probing and checking, but throwing parts at a problem often gets us in trouble.

I had to hunt down an original style MAF to get rid of my Code 36 in my L98. The hot film style just didn't return the right voltage to the computer when it was monitoring the burnoff cycle.

How many times have you replaced the relays? If they both went down and have multiple times, you might have a grounding issue or wiring issues.
KyleF is offline  
Old 12-12-2018, 08:34 PM
  #8  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default checked the basics ...

Well I had a chance to check some basic things. When it was in a no-start condition I put a timing light on no 1 wire and I got a flash so I have enough spark to signal the timing light. I also checked the fuel pressure 45 with the key on and 40 while cranking and the pressure held for 20 minutes.

I got a new MAF power relay and it didn't help the no-start condition so I think the relay is OK so now I have a spare. Running out of ideas. Back to the FSM Cranks but won't start section.
rharker is online now  
Old 12-13-2018, 11:38 AM
  #9  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 138
Thanked 9 Times in 9 Posts
Default

Originally Posted by rharker View Post
Well I had a chance to check some basic things. When it was in a no-start condition I put a timing light on no 1 wire and I got a flash so I have enough spark to signal the timing light. I also checked the fuel pressure 45 with the key on and 40 while cranking and the pressure held for 20 minutes.

I got a new MAF power relay and it didn't help the no-start condition so I think the relay is OK so now I have a spare. Running out of ideas. Back to the FSM Cranks but won't start section.
Code 33/36 Should not cause a no start issue. Both of these are MAF related.

Did you put the old MAF back on and try to start it?

Here is a thought.. the Ignition Control Module can often be affected by heat when it starts to go. This can also cause a no start condition if it goes out. Not sure how it would drive a code 33 or 36.

My L98 had a 33 or 34 when I had a fuel rail leak and became very hard to start, if at all... until I smelled the gas and located the leak. You may have the opposite and have a air leak and too lean to start. Does it fire any cylinders while cranking or just nothing?
KyleF is offline  
Old 12-13-2018, 11:54 AM
  #10  
tequilaboy
CF Senior Member
 
tequilaboy's Avatar
 
Member Since: Aug 2003
Location: Lakeville MI
Posts: 2,317
Thanks: 0
Thanked 24 Times in 22 Posts
Default

Both failures point to a MAF voltage issue...likely high voltage in both cases...

The car is probably flooded due to the high MAF signal at start-up. Hold the throttle wide open to start, if it won't fire with closed throttle to clear the flooded cylinders.

Then go about diagnosing the high MAF signal. Possible causes: open circuit on MAF signal wire (signal is pulled up to 5 volts by ecm), bad power relay, bad MAF...log the unlimited airflow signal during cranking and after shutdown if you can.
tequilaboy is offline  
The Following User Says Thank You to tequilaboy For This Useful Post:
rharker (12-13-2018)
Old 12-13-2018, 12:00 PM
  #11  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default

Originally Posted by KyleF View Post
Code 33/36 Should not cause a no start issue. Both of these are MAF related.

Did you put the old MAF back on and try to start it?

Here is a thought.. the Ignition Control Module can often be affected by heat when it starts to go. This can also cause a no start condition if it goes out. Not sure how it would drive a code 33 or 36.

My L98 had a 33 or 34 when I had a fuel rail leak and became very hard to start, if at all... until I smelled the gas and located the leak. You may have the opposite and have a air leak and too lean to start. Does it fire any cylinders while cranking or just nothing?
Yeah I put the original wire MAF back on and it behaves the same. It cranks sputters and tries to start and sometimes runs for a couple seconds then dies. Code 33,36. I was thinking about the ICM too but I was getting spark. This is an intermittent problem because sometimes it will start with no SES and run for a minute before sputtering out and dying.
rharker is online now  
Old 12-13-2018, 12:13 PM
  #12  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default

Originally Posted by tequilaboy View Post
Both failures point to a MAF voltage issue...likely high voltage in both cases...

The car is probably flooded due to the high MAF signal at start-up. Hold the throttle wide open to start, if it won't fire with closed throttle to clear the flooded cylinders.

Then go about diagnosing the high MAF signal. Possible causes: open circuit on MAF signal wire (signal is pulled up to 5 volts by ecm), bad power relay, bad MAF...log the unlimited airflow signal during cranking and after shutdown if you can.
I tried to clear it by using full throttle and it behaves the same but only sputtering.
rharker is online now  
Old 12-13-2018, 12:24 PM
  #13  
tequilaboy
CF Senior Member
 
tequilaboy's Avatar
 
Member Since: Aug 2003
Location: Lakeville MI
Posts: 2,317
Thanks: 0
Thanked 24 Times in 22 Posts
Default

Do you hear the fuel pump running during the 2 second prime cycle just after ign on? Maybe a bad fuel pump relay. MAF (power relay) gets its power through the fuel pump relay or oil pressure switch.
tequilaboy is offline  
Old 12-13-2018, 02:48 PM
  #14  
rharker
CF Senior Member
Thread Starter
 
rharker's Avatar
 
Member Since: Nov 2007
Location: Gainesville FL
Posts: 1,418
Thanked 55 Times in 53 Posts
Default

Originally Posted by tequilaboy View Post
Do you hear the fuel pump running during the 2 second prime cycle just after ign on? Maybe a bad fuel pump relay. MAF (power relay) gets its power through the fuel pump relay or oil pressure switch.
I can't hear the fuel pump but I see it jump right up to 45psi immediately after I turn the key on. It turns out that my ICM was bad or intermittent. I put a new one in and have had the car running for 1/2 hr no stumbles no codes.. Now if anyone can explain how a bad ICM can trigger those codes, I'll be grateful. Thanks everyone!
rharker is online now  
Old 12-13-2018, 08:37 PM
  #15  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 138
Thanked 9 Times in 9 Posts
Default

Originally Posted by rharker View Post
I can't hear the fuel pump but I see it jump right up to 45psi immediately after I turn the key on. It turns out that my ICM was bad or intermittent. I put a new one in and have had the car running for 1/2 hr no stumbles no codes.. Now if anyone can explain how a bad ICM can trigger those codes, I'll be grateful. Thanks everyone!

Not sure, but glad you figures it out. Usually ICM issues are a Code 42.
KyleF is offline  
Old 12-14-2018, 07:56 PM
  #16  
DUB
CF Senior Member
 
Member Since: Apr 2009
Location: Charlotte NC
Posts: 19,263
Thanked 2,347 Times in 2,043 Posts
Default

Glad to read you got it working.

DUB
DUB is offline  
Old 12-16-2018, 03:00 AM
  #17  
catso
CF Member
 
catso's Avatar
 
Member Since: Mar 2017
Posts: 51
Thanked 5 Times in 5 Posts
Default

Originally Posted by rharker View Post
I can't hear the fuel pump but I see it jump right up to 45psi immediately after I turn the key on. It turns out that my ICM was bad or intermittent. I put a new one in and have had the car running for 1/2 hr no stumbles no codes.. Now if anyone can explain how a bad ICM can trigger those codes, I'll be grateful. Thanks everyone!
I would think that the codes seem to be a by-product of the misfires or slightly out of sequence spark. The more sophisticated OBD2 system would be able detect it, but of course OBD1 cannot.
catso is offline  
The Following User Says Thank You to catso For This Useful Post:
rharker (12-16-2018)


Thread Tools
Search this Thread
Quick Reply: codes 33 & 36 suddenly won't run


Sponsored Ads
Vendor Directory

Contact Us About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: