I have an intermittent Code 33 problem with my stock 86 coupe A4. I know that Code 33 means high Maf voltage @ less than 2500 rpm. It has happened twice ,usually after the car has not been started for ~ two weeks. I can scan for the code and it then clears up. While the code is active the car runs poorly , so I know it is real. I have a factory manual and what it is leading me to is an intermittant fault. I think at this point , I may have a sticking MAf relay, Maf burn off relay or maybe a poor wiring conection . I don't think the MAf itself is bad, because it is running very well right now and I have verified that the wiring connector at the Maf is OK . But it will happen again.
Has anyone ever tracked this one down? I know that I will probably have to follow the diagnostic ladder in the manual, but I was hoping someone could point me in the right direction since I refuse to start throwing parts at it. I hate intermittant problems !!

 

Most members will tell you to switch out the relays first. They're less than $30 to try. Make sure the connections are clean and making good contact, too. 'Intermittent' could be a loose wire or something.

I doubt it's the MAF. @ ~$300 I hope not!

 

,but if that's not the problem I'd replace both relays NOT just one.

 

Try the relays and also check the green wire on the MAF plug in and ensure its tight and not broken.Also check the wire connectors at the relays and see if the rubber tubing pulled back exposing any bare wires that can touch each other at times.(doubt thats the problem but is a common problem on C4's at the relay connections)

 

You really need to go through the diagnostic procedure on this one since it is almost always an intermittent condition.

The scary thing about code 33 is that the oil pressure switch is in the circuit. Under certain circumstances, low oil pressure can cause this code to set.

Since you say it happens after the car sets up a few weeks I would ask some questions about oil changes. How often do you change oil and when you do, do you drain it while the engine is hot?

The reason for this question is that many think that since they don't drive the car much, they don't need to change the oil very often. By doing this, oil can gum up around the oil pickup and cause intermittent oil pressure problems. The oil pressure loss can be so quick that you won't pick it up by watching the gauge, but it only takes a fraction of a second of power loss to the MAF to set this code.

If you do suspect the possibility of gummy oil in the crankcase. Do a hot oil drain, change filter and fill the crankcase with universal grade oil. This is oil that is especially formulated for diesel engines with LOTS of detergents for soot dispersal. What most people don't know is that this oil is also certified to the highest level for gas engines as well. Run the oil several hundred miles then drain it thoroughly and pull the drain plug while the engine is HOT. Do it a second time and then go back to your favorite oil and keep it changed.

Examples of universal grade oils are: Chevron Delo 400 Multigrade, Mobil Delvac, Mobil Delvac One, Mobil Truck and SUV oil and Shell Rotella T. The Shell Rotella T has the highest parafin content of these oils, so it is not the best choice for cleaning your engine.

Hope this helps,

 

I never thought about that kind of scenario. I'm about due for an oil change. BTW, I always drop the oil hot. I recently did the valve seals and the top end is clean so I don't think sludge is an issue.
The engine carries ~ 55psig oil pressure , but I know sitting will result in most all of the oil draining back into the pan. Could this problem be caused by no oil pressure on initial start-up after a two week hiatus?
Based on the other excellent replies, I plan to replace the burn off relay and Maf relay as well since they are 20 years old and are most likely sticking.
Thanks for all the excellent advice.

 

dwestsr,

Great! You agree with my motto, that is "Change oil hot and change oil often."

Now that we have the gunked up crankcase out of the way as a possibility, the oil pressure connection, among several other connections could be flaky. Check connections on; the oil pressure sender, MAF, MAF power relay, Fuel Pump Relay. For good measure, also check the connection at the Burn Off relay. Don't forget the grounds and power feeds for these circuits.

Best of luck,

 

I wanted to post an update and say thanks for the help. The Code 33 turned out to be a bad Maf relay. I ran throught the Helms diagnostic ladder and Voila! While I was in there I also changed out the Maf burn off relay , figuring it couldn't be far from failure as well. Performance and gas mileage have returned to normal. Thanks!