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MAP and Code 34, Chilton's not helpful here!

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charley88

Guest
Car has been running rough with backfiring on acceleration. On the highway, runs o.k. (definite loss of H.P. though) Ocassionally losses idle and stalls when not in gear. Could trace problem back to blocked Cats, which are now not an issue. Wondering if loss of back pressure causing all my problems. (New exhaust is 2nd on list of repairs unless I learn otherwise) Car sounds like it's out of time. I didn't want to start adjusting the timing until I know all my sensors check out. Car gives me an intermittant check engine light and code 34, whether present or not car runs the same. I can't find the MAP sensor, I'm going crazy looking for it to test it. Car is stock L98, plugs and wires are two years old, IAC O.K., TPS O.K. no obvious vacuum leaks, new O2 sensor. Alternator now on it's way out giving me up to 18 volts on my dashboard gage. This is a very new problem, I don't think they are related.
I've been reading all of your posts over the week and have learned a lot. Hope you can help with this one.
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
If its an 88 it has no MAP. ...84 and 91 thru 93 have them.
85 thru 90 have MAF mass air flow ,thats the code 34
 
C

charley88

Guest
It definitely feels limp!! When I disconnect the MAF the car makes a noticeable change for the worse. Does this mean it is working? What about the exhaust back pressure, any thoughts?
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Well if you have to MUCH back pressure

The car will run like Do-DO and you have 3 cats ( 2 pre cats & 1 main )


If the car sounds like a hoover.. chances your cats are plugged.


Go to the local muffler shop and for like 40 bucks.. they can test the system.


Vig!
 
C

charley88

Guest
There is no resistance from any of the three cats, they all met the same fate.
 

maxrevs85

Well-known member
Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
Dont count out the alternator problem . Correct voltage is pretty important. There are also MAF relys, actually burnoff module .It provides power to the MAF sensor and burns offf (cleans) the sensor wire after the engine shuts down. The Haynes manual explains this system pretty well.
 
G

greg

Guest
I have replaced the two relays , twice on my 87, maf burn off- near the battery. The car ran good after this. They are $18 each.
 

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