Normal misfiring LT1, no power, weird exhaust sound. I am going thru the usual suspects(it might be the cats) but if I hit a wall, any recommendations?
Thanks in advance.

 

what year is your car?

if its obd1, which is 94 or 95 year model, and if you own a laptop, you can get an aldl cable and run diagnostics yourself, the cable runs like $60 and the software you can download for free.. its well worth it...


i had a bad miss when i first got my car running.. i bought a cable, downloaded freescan, hooked it up to my diagnostic port and scanned it, i had 6 codes.. basicly it told me my knock sensor wasnt correct, and i had a right bank heated o2 sensor that was bad..
i believe it paid for itself with that one scan..

 

Thank you, it is an OBD1, a 94. Are the codes any different than using the paperclip method(which I did, no codes displayed.)

 

that i dont know, i used an obd1 code list.. and freescan lists a small detail of the trouble code...

 

You can not flash the codes on a 94 by shorting the ALDL connector pins. 1993 was the last year that worked. You need a true OBD-I scanner, and you can read the trouble codes (see Shoebox's LT1-specific list)....

http://shbox.com/1/Dtcs.htm

......and read the various sensors and calculated PCM parameters. Actron and AutoXray, among others, make OBD-I scanners that can do this. There is also an LT1-specific scanner called the Scanmaster LT1 that is useful.

A good alternative to a hardware scanner is free scanning software and a cable to connect a laptop to the ALDL connector. The available software includes:

FreeScan (free):

http://andywhittaker.com/ECU/FreeSca...0/Default.aspx

TTS DataMaster (free download and 20 free uses):

http://www.ttspowersystems.com/DataMaster.html

EFILive V4 (purchase):

http://www.efilive.com/index.php?opt...=48&Itemid=133

Cable:

http://www.akmcables.com/

There is a similar OBD-II system available from AutoTap, and several other suppliers.

 

Thanks Injuneer, is that the case for all 94 LT1's or just the F bodies, mine is a Corvette. Shame you are not 3000 miles closer, otherwise I would buy you a few beers to take a look at this thing.

 

I just got to rep San Jose, Ca The Heart of The South Bay

 

According to How To Understand, Service and Modify CORVETTE Fuel Injection by Charles O. Probst, 93 was the last year shorting the pins on the ALDL connector would work on a Corvette as well. You will also have to use a different code list for a Corvette PCM, because in 94/95 the Corvette used the so-called OBD-1.5 PCM, and has a different DTC list than the 94/95 F-Body PCM.

The Probst book may be wrong - I've found a few mistakes in it (e.g. - description of open vs. closed loop).

 

Cured it, it was the coil! The info on this site is great!
Here is a rundown of what happened and what we did:

Symptoms: At first, a miss that worsened in higher gears and lower RPM's, starts fine, horrible gas milage, loss of power,bucking and surging, funny exhaust sound. Then the above symptoms plus hard stating, lastly no start with backfire when you stop spinning the engine.
Checked the codes using the paperclip method, no stored codes, C12.
Checked fuel pressure, 41 psi normal.
Checked spark firing by cranking engine with spare plug on a disconnected wire, sparks visable.
Checked plug and coil wires for obvious frays, OK.
Followed this thread for diagnosis:https://www.camaroz28.com/forums/sho...d.php?t=601565
We go thru the steps with a Multimeter and it comes down to the MSD coil or ignition fuse, fuse checks out.
Check the coil and sure enough, instead of the resistence being between 5000-7000, its .2 http://shbox.com/1/coil_testing.jpg
Put new coil in and it fires up! :http://shbox.com/coil/coil.html
You really need to track these things down methodically with a multimeter.
Many thanks to Bryan