I checked my dad's 87 Corvette today for codes because the SES light was coming on. This is what came out ...

1. 13 - Oxygen sensor signal problem or loss

2. 34 - MAP Sensor voltage high - pressure high/vacuum low
34 - MAF signal high - flow low (EFI/TPI/SFI)

3. 44 - Oxygen sensor lean error


Its an 87 'Vette TPI with an Automatic Tranny. I am on my way to the parts store to get a new Oxygen Sensor, any other ideas? We just bought the car so I figure its a good idea to swap in a new Oxygen sensor even if it's not the problem.

Any suggestions welcome.

Thanks,

Kurt

 

Anyone???

 

Kurt ,

Hopefully, you're on your way to the parts house and not reading this yet...

(Jeopardy theme music playing in background)

OH! You're back. Get the new oxygen sensor installed (don't forget the anti seize compound) and reset the ECM by removing power for about five minutes (long enough to clean the battery terminals and cables).

Once the sensor is installed and the engine has been long enough to warm up, scan for error codes again. If you get the '34' again, we can deal with that. Don't just run out and pick up a new MAF.

 

Vader, good to see you buddy.

Got the O2 sensor in, and the ECM reset (just took off the negative terminal for about 15-20 seconds).

Codes 13 & 44 are gone. But I didnt take it for a ride, I just let it idol for a while.

What's the next step? I don't want to go buy a new MAF. Please give me some ideas of where to troubleshoot.

Thanks a ton,

Kurt

 

Oh yea, and while I'm on here ...

Which #34 are we dealing with? The MAF, not the MAP - right? Just wanted to make sure I am clear in the head.

- Kurt

 

KZ,

You are correct. There shouldn't be a MAP on an L98, so the MAF codes apply to that vehicle. Your '34' means that the MAF is reporting a lower intake flow than the ECM expects at a given engine RPM and throttle angle.

Make sure the MAF is connected electrically. Make sure it is getting 12V on the 'E' terminal. Grounds are on the 'A' and 'B' terminals. If not, check the MAF power and burnoff relays. If the correct voltage is present, proceed.



Closely inspect the intake dustwork and the intake bellows at the throttle body for cracks, splits, or other openings. Ascertain that the MAF itself is well sealed to the ductwork, Make sure you have the correct PCV valve and all vacuum hoses are intact. Be sure that the oil filler cap is seald and is NOT a breather type. Make sure the EGR valve is sealing and not leaking through. Any leaks will lower the amount of air being measured by the MAF. You might want to temporarily disconnect and cap the vacuum line to the power brake booster as well, since it can be leaking internally.

Set the TPS voltage to no more than 0.61 VDC - 0.54V is ideal. This will tend to lower the intake air expectation of the ECM.

Once those are checked, let us know if you still generate the errors. Does the code set immediately when you start the engine of after a bit of driving?

 

Vader -

I appreciate your wisdom.

We took the car on a nice long ride last night, and tonight I had it to drive around town. The check engine light has not come on at all. I think the problem's fixed.

In reading your post, however, I got to thinking. When we bought the car, the previous owner showed us that he had broken the plastic piece that surrounds the air filter. He has it fastened with wire ties or something cheap like that. Could this be a problem, or something that should be fixed?

Thanks for your help. I will still probably check the voltage in terminal E, just for ***** and giggles. I am going to Myrtle Beach for a week, and won't be around to reply.

Thanks again,

Kurt Z.

 

You should probably repair it. I'm not sure what the '87 'Y' car has for an intake tract, but if you have the inside-out ("garbage-can") type air cleaner like the Firebirds had in that year, you could be sucking unfiltered air into the engine. If the crack is somewhere after the MAF sensor, you could definitely generate a '34' from that.