What to replace first

[Dunn1]

I have a late 86 coupe showing codes 33,34,36. What should i replace first. Please Help.

Brian

 

[toptechx6]

Don't replace anything until you diagnose the problem. Trouble codes or DTC's do NOT necessarily indicate a failed part, only that there is a problem in that circuit. You will need a Factory Service Manual to troubleshoot correctly.
Best practice is to start with the lowest numbered DTC first, once repaired by following the flow charts in the FSM clear any remaining codes then road test to see if the others return.

 

[hotmtrsports]

Well stated toptechx6

You're car is an excellent example:

Code 33 = Mass air flow sensor (Voltage Low)

Code 34 = Mass air flow sensor (Voltage High)

COde 36 = Mass air flow burn-off sensor fault

So there's an error somewhere at the mass air flow sensor

By any chance did you have a K&N Air filter, cleaned it...re-oiled it, then re-installed it?

Chuck M

 

[vetteoz]

once repaired by following the flow charts in the FSM .

like this

batee.com - 1984-1989 C4 Corvette Electronics Repair

At a guess ( as above , don't guess ; diagnose actual problem ) the code 36 ( burn off circuit fault ) is causing the the other two codes because the burn off relay is not cleaning the MAF like it is supposed to

 

[Dunn1]

Thanks for the reply's. Started the car this morning no check engine light. Drove the car about 3 miles slowed for a stop light and the car stalled no check engine light. Tried to start the car and it started and stalled 3 times then started and ran and check engine light came on. I made it home and checked code it was 34. Let the car set for about an hour and started the car ran great with no check engine light. drove it about 5 miles with no problems. Ran out about 5 pm to got to the store and about 3 miles down the road same problem stalled with no light and after about 4 or 5 start and stalls check engine light came on and it ran home same code 34!

Help Brian

 

[rcr29kh]

Well stated toptechx6

You're car is an excellent example:

Code 33 = Mass air flow sensor (Voltage Low)

Code 34 = Mass air flow sensor (Voltage High)

COde 36 = Mass air flow burn-off sensor fault

So there's an error somewhere at the mass air flow sensor

By any chance did you have a K&N Air filter, cleaned it...re-oiled it, then re-installed it?

Chuck M

Chuck have you seen problems after servicing K&N's?

 

[toptechx6]

Thanks for the reply's. Started the car this morning no check engine light. Drove the car about 3 miles slowed for a stop light and the car stalled no check engine light. Tried to start the car and it started and stalled 3 times then started and ran and check engine light came on. I made it home and checked code it was 34. Let the car set for about an hour and started the car ran great with no check engine light. drove it about 5 miles with no problems. Ran out about 5 pm to got to the store and about 3 miles down the road same problem stalled with no light and after about 4 or 5 start and stalls check engine light came on and it ran home same code 34!

Help Brian

The diagnostic process remains the same no matter how many times the light comes on, whether it goes off at times or how many miles are driven between occurrences. The random nature of the symptoms might indicate an intermittent problem such as a loose connection, bad wiring or failing relay, but the diagnostic flow charts in the FSM will still be your best starting point because they show the components and wiring involved and will explain what specific conditions cause code 34 to be set. Good luck.

 

[hotmtrsports]

"Chuck have you seen problems after servicing K&N's?"

When you recharge your K&N, make sure there is no excessive oil still in the filter. Let it sit overnight on newspapers or something like that to soak up the excess.

If there is more oil than needed, it can raise havoc with the sensors and even make them fail.


Chuck M