I have an '85 Corvette which has the newer 165 ecm in it. I am just getting it running again after an intake change. When I start it, sometimes it will smoke black and the idle is hunting all over the place along with it being unable to rev like it should. If I unplug the maf the idle drops but it will then idle within a 10-20 rpm spread and will rev like it should. Does this sound like a bad maf to you? I accidentally dropped the maf when the engine was apart so I'm thinking that's what happened to it.

 

kinda sounds like the maf butter fingers ! Are you getting and maf codes ?

 

HAhaha, I called myself a lot worse than butterfingers. Yes it threw a code 33 but I was disconnecting it while it was running so I thought that was the reason. Upon further testing today I found I have no ground to the maf so I'm going to have to double check my wiring on the relays tomorrow

 

The black/ white on pin A of the maf is the maf ground it goes to d1 of your 165 .

 

I know that wire is where it's supposed to be because I went over the re-pinning instructions today, I'm going to have to look at the relay wiring and check the black/white wire for continuity. I'm hoping it's a screwup done by me, I really don't want to shell out the bucks for another maf.

 

there are alot of guy parting out thirdgen here in the classifieds you might be able to pickup a known good bosh for $50-60.

 

Once I get the wiring straight I'll know if I will need one or not. Curiosity has got to me, I'm heading back out to the garage now to see what I can dig up. Thanks for coming to my rescue again, I owe you.

 

I didn't do anything but will crack open a beer if that helps you lol

 

I think the code 33 can also be thrown if there is no signal back to the ecm b12 or I have seen it thrown with a mild cam during cruse if the threshold goes over 45gps programing can fix that.

 

I can't believe what I just found. How can a person do the ecm re-pinning and not make a mistake but when it comes to wiring up 6 wires from the old burnoff connector to the new relays he can get it AFU.
I'm done for tonight, I'll re-wire it all tomorrow, thanks for cracking open that beer, it got me back on track,

 

moved onto wine for dinner waiting for you to go do your home work lol

 

I have been in the garage all day tracing wires. I think they are all okay but now my maf connector is completely dead so I am wondering if I have a bad relay. Is there a procedure to check these? I have the fsm for my car but it is no good for this info. Also, should the big orange wire to the ecm be hot all the time, key off?

 

 

The top of the relay should show the schematic it does not matter if d and f is reversed in polarity.

 

What's on the top of the relay is probably part of the problem, it says Made in China. I'll try tomorrow using the diagram you posted.

 

I more fond of the newer style relays like acdelco 15-8240 pigtail, PT1115 gm/acdelco 4089936, 14103304 , 15-8240 they are heavy duty and have weather pack seals on them.

http://www.eecis.udel.edu/~davis/z28/ecm_swap/

 

I have the relays out of the car, is there a way to test them to see if they are good?

 

are they the older style ones on the left in this picture with no weather seal on them ?

 

Yes

 

https://www.thirdgen.org/forums/tpi/...nces-they.html

Let me go see if I have any old ones to let you know what each post is.

 

I only have a old gm burn off one that the schematic is not shown, But I can give you the information another way.

 

I'm all ears.

 

This is the mass power relay, The black/white wire and the tan /white control the relay the black/white is the ground if you get these reversed the relay will still work. you can see in the schematic it is always shown as a n/o circuit so when these 2 leads I mentioned above are not powered pin e and c are connected and when powered e and a connect.

 

I'm about 99% sure all the wiring is okay but since the maf connector has no power to it I can only guess it is a relay, that is why I was wondering if there is a way to check the relay off the car. Such as putting power to one terminal and grounding another to see if it clicks or whatever.

 

This is the burn off relay the orange(the one next to the blk) and black are the relay control wires .a and e are open apply power and ground to the orange and blk and a and e will connect and have continuity between these 2 terminals.

 

I hope all that jibberish makes sense

 

Yes it does, now I know what I am going to be doing tomorrow.

 

going fishing

 

Yep, fishing for what I screwed up while re-pinning the ecm. I'm hoping that is all it is. I remember when I was doing it I was comparing the wire colors in the fsm with what was on the car and there was a gray wire that was not supposed to be gray according to the fsm but I can't remember now what color that wire was supposed to be, the car has never had any wiring done to it it is all oem.
I'm starting from the beginning again today then see if I can spot the problem. I knew I should have found somebody to do this, I hate wiring.

 

There was a supplement for the electrical for the 85 f-body that came out shortly after the helm so maybe the same for the y-body. You can always print out this link and ohm out all the wires just cross them off the pictures after you test each one. Best of luck finding the wiring issue.

http://www.chevythunder.com/maf_sens...rcuits%202.JPG

 

Following that diagram will be one of my activities today, testing for continuity. I'm thankful there weren't that many wires involved in the re-pinning. I'll probably be back tonight either happy as a pig in s**t or po'd to the max. Thanks for sticking with me. It's time.

 

Thank you for the wiring diagram. I've got a code 33, and after replacing the burn-off relay and the MAF, I now see that there's ANOTHER relay I need to check. The wiring diagram I had made me think the orange/orange/dark blue/black was the cooling fan relay. The two MAF relays are beside the fuel pump relay, correct?? Drivers side of the engine compartment, in the corner under the hood hinge? (88 Firebird wiring harness, if it matters, L98 engine)

 

yes your in the right spot for the maf power and burn off relay's.

 

 

Yeah, I followed through the flowchart, and got to "Check all related connectors for making good contact. If OK, MAF is faulty" but this is the second MAF to throw this. I'll have to dig a little deeper when I get home tonight, but the burn-off relay is still the old one (replaced the MAF power relay). I saw somewhere else to look for a vacuum leak under the intake (rubber elbow).

 

I'm not sure if you have read this post.
https://www.thirdgen.org/forums/tech...ible-code.html

 

No, I hadn't seen it, but it makes sense... Why do I always get the really good info to try when I'm stuck at work!?

 

Time to go home sick and have a long weekend

 

I would, but I'm the only tech in today. I do have a week off coming up. Really need to redo the top end gaskets on the engine (have them, just haven't found the time to do it), too.

 

I think I found my problem, I have all the wires right now, (I hope). Your last line in your response is my only gray area now and I'm sure it has something to do with that beer you opened. You have e & c connected when not powered, then you have that when power is applied e&c connect, anyway on my power relay the e&c are connected no matter what power or not. I have a new one coming tomorrow morning so maybe this ordeal is coming to a close.
Ooops my mistake, I re read your response, I stand corrected

 

I was just going off the schematic It maybe incorrect but you can see the connection on the maf power relay on post #13 e and c are connected when powered the connection changes to a and e. It could have been the beer just sayn

 

No, it was my mistake, I have been looking at wire numbers & colors so long my eyes are crossed. I misread where you covered two different wire positions, e&a and e&c. And I haven't even had a beer,,,maybe I better. At any rate, I am done until tomorrow morning.

 

Just checked my MAF... just a bit over 22K across pins D & E. So, looks like a trip to the parts store with my multimeter...

 

Finally got the parts store to give me the correct MAF. Had to get the one for an 85 Vette. Was seeing about 1.8V at idle on the one the parts store said was the 'correct' unit.

With the Vette MAF, I'm seeing about 260mV at idle on pin C (middle pin). Anyone else who is having trouble, check pin C (between C and ground), and see what your voltage is. If the ECM sees over 2.2V at anything less than 1/4 throttle, it'll set a Code 33. You should be seeing well under 0.5V.

Took it for a test drive, and once the computer relearned, everything is good. tunedperformanc, thank you for your help on this.