Hello, all, new to the forums, but not new to camaro's. Have a 67, had a 73 split bumper, a 77, and my new well new for me 1995.

Quick overview.

Bought this with a blown head gasket. Ripped it all apart, had the heads milled and valves redone. Just got it all back together, what a pain in the ....

Fired it up, idled a little rough. When I put it in gear it backfired like crazy. I readjusted the valves, and found a loose wire on #8, and a broken wire on #6. Fixed those issues.

Now when I fire it up, it idles much better, however I still get a small backfire not as significant as before.

Here is one thing I did notice, when I first start the car, the tachometer starts out around 500 rpm, and it runs smooth as can be, then the tachometer goes down to about 0, which is impossible, the car is running, and starts running a little rougher.

Any suggestions on what I should look into first. I am sure it is not motor related.

What sensor reports the tachometer speed?

Thanks.

 

Probably optispark, it's harness or plug wires routed incorrectly.

 

Shoebox,

Thanks for the reply, BTW, found your website, and thank you so much for having that. Was very helpful for my failing memory when putting things back together! Which wasn't too bad, I found labeling everything helps. But the shop that did my heads threw all the bolts in a bag, and thanks to your diagrams I was able to know which bolts went where!

I am thinking it is something electrical as well. I did check to make sure I didn't have any crossed wires coming off the optispark was well. I did find one bad wire, and a loose one on the plug, which helped things out. I am off to get a spark tester to verify the wires are good, I think that would be my first step.

I was thinking of buying a scan tool for like 220 bucks, since this is an OBD1 system, that uses the OBD2 plug, my only option is to get a somewhat decent one. Is it worth the investment to help my diagnose the problem?

Thanks!

 

Its not worth it. Take it to Advance Auto or Auto Zone or a decent neighborhood garage. Most will scan it for free.

If you have a laptop - download FreeScan and purchase TunerCat. Can scan your own codes AND tune your own PCM later down the road if you modify the car. Wouldn't cost much more. Around $100 in software, and $70-$90 for the correct cable to go from RS-232 Serial Port or USB to the OBDI or OBDII connecter.

 

You don't need a high-end OBD-I scanner to scan via the 95's 16-pin ALDL connector. Some scanners come with adapter plugs. If you don't have an adapter, simply jumper the connectors as shown on Shoebox's site:

http://shbox.com/1/xraycable.jpg

You can get a used AutoXray OBD-I scanner fairly cheap. TTS DataMaster is another OBD-1 LT1 scan software:

http://www.ttspowersystems.com/

 

Thanks for the input, I may look into the software, I could probably make my own connector, I do that kinda stuff all the time.

Just an update. I was replacing the plugs, and checking spark, and found #2 was a little weak, brownish, and #4 was not firing at all. A quick trip to the store, and 60 bucks later, I replaced the #4 wire first, and found that it is intermittent, took it out for a ride, and no backfiring, and was running way smoother...

After about 15 minutes, I shut it off, and then it wouldn't start. Nothing. Let it cool down for a couple of hours, and it fired right back up, drove it home, and it was dead again when trying to restart it.

So today, if the rain holds off, I am going to replace the coil first, I think that would be the logical step before ripping everything apart to change out the opti-spark. Might as well have all new ignition parts anyways!

Believe me, after doing a head gasket change out on this car, I do NOT want to take ANYTHING apart for a few days until my hands heal up.

The worst was the EGR pipe off the right hand exhaust. I figured I could put it on after everything was done. Three hours later, scrapes, and skin worn off my wrist later, I finally got that damn bolt caught, and tightened 1/4 turn at a time!

 

I saw the free Scan software, but can't find a diagram for the cable to build.

I bought a OBD-1 unit, and when I opened it, it does not have the same pin out as shown on shoebox site... What do I do now to get the damn codes?


UGH!

 

Does the scanner have a 12-pin connector? If its OBD-I, by definition, its got to have the pins arranged the way they are shown on Shoebox's site.

How are the pins arranged in the connector on the unit you bought?

 

No idea where you are located but might look into eliminating the EGR if you are not worried about emissions.

As for your coil, I would suggest the opti. Seems that would make sense but since you are not getting a SES light (you don't indicate so) this is interesting. Also you should at least have it scanned to check codes. I do suggest getting the software yourself however so you can log runs and see what is going on.

 

Thanks for all you input, the car is running fine now.

Replaced the coil, plugs, wires, and Opti-Spark. Purrs like a kitten now.

Also found the trouble code for the TPS, so I changed that as well. Now the only issue is at idle, the left 02 sensor is down to 13mv. Guess I'll change that too...

Again thanks for all the input..

 

BTW, Autozone, can not scan the codes from a 1995. It is OBD1, with OBD2 connector.

I built a custom cable, and used pcmcomm software to get codes, and diagnostics. I had the RS232 cable, and needed 3 resistors, 2 transistors, and 1 diode and some wire to get this all hooked up.

I guess my electronics school did pay off!


Thanks again!