It's gotten to the point I can't drive more than a mile from my house because I won't make it back. I can't believe with a problem that bad I can't fix it. I guess I am going to pull the opti off and look inside. This is ridiculous.

 

Do that.

 

My car has been doing this for the last two months - I agree that it's ridiculous. Especially when you don't get a check engine light to steer you in the right direction.

Lately, I've made a point to look if the 93 - 97 Camaro's I see on the road in my area are Z28s with the LT or the plain jane 3.8 ltr V-6s. 95% are the V-6s. I now know why.

 

Well, we going to pull the car into the garage tonight to pull the opti off but it won't run. When you start it, you have to give it atleast half throttle to get it to run. thats exactly what it did before when it got hot after driving it for 10 minutes

When you turn the key on, but not to the start position, the aftermarket tach sweeps all the way up to 8 grand then goes back to zero and you can hear a pop from the engine, the factory tach jumps but doesn't go to 8grand.

I checked the fuel pressure it's 43psi, I put spark tester on one of the plug wires and and with the key on, not in the start posistion, something is telling it to fire. And everytime it fires the tach jumps to 8grand(thats what the popping noise was). When you try to start it, the spark gets really weak and thats when you have to give it so much gas and it starts back firing and running really bad.

I am glad its running like this, maybe I can actually find out whats wrong with it.

Any ideas?

 

I finally noticed you mentioned an aftermarket tach and back on a previous page you referred to a "white/black wire" as a tach wire. If you're referring to the white/blk wire from the coil to the ICM, you can't just plug a tach into that wire.

If you have anything added or spliced or anything other than stock on the ignition, REMOVE IT.

 

Yeah, i think thats where the tach wire is. What damage can it do? I am wondering if it's taken out something, opti?

 

Well remember when you said
"When you turn the key on, but not to the start position, the aftermarket tach sweeps all the way up to 8 grand then goes back to zero and you can hear a pop from the engine, the factory tach jumps but doesn't go to 8grand."

and this jewel
"I put spark tester on one of the plug wires and and with the key on, not in the start posistion, something is telling it to fire."

Again I say take off all the aftermarket devices and especially the ones that are "rigged" into the wiring. Your spark issues are due to the fact that you are piggybacking items on the ICM lines used to fire the coil.

Look at this
http://shbox.com/1/95_ign_system_schematic.jpg

Notice the pink/black wire and white/black wire between the ICM and the coil. When the ICM triggers the coil to fire, it pulls one or the other line low to do so. (I don't know which). Your 'rigged" wiring is obviously doing so before it should. It may also have the effect of increasing impedance on the system to point it can't fire when it should. Not entirely sure but you should remove anything stuck on those wire.

As far as would it kill the opti. NO. But it could (could) kill the coil or the ICM.

 

I cut the aftermarket tach wire off, still won't start. I will swap out the ICM and the coil to see if that makes a difference.

the tach has been on there for 6 months before it started running bad, I have already swapped the computer, ignition control module and tried a different coil.

Now it won't start at all unless you open the throttle all the way.

There is a MAP high voltage code, but I don't know if thats just because how it's running and backfiring it caused that.

 

Before you go throwing parts at it, why don't you do some analysis?

You can very easily test the coil to see if it is bad but first why don't you see if you have spark consistantly from a few plugs.

More than likely you have an open circuit on the black ground wire going to the MAP. confirm there is 5 volts from grey to black. If the black wire is broken it won't read 5 volts or have continuity when measured to ground.

This will not stop it from starting since the PCM will default to backup mode and refer to a table for the MAP value.

As mentioned before you should start looking for the basics. Spark, fuel pressure, injector signals, compression etc.

If you have spark, try squirting fuel directly into the intake and see if it cranks up. If you have spark, compression and you throw fuel in the intake and it still won't start, get back to us for ideas.

 

I've had it. I went to start the car today and it started. There wasn't anything different than the other day except I charged the battery. It has a drain that I haven't been able to find yet. As usual the car ran good for about 15 minutes then I about didn't make it home again.

Fuel pressure is good at 43psi.

When it sits and idles after it's running bad, at one point the ST fuel trim was 92 on the left and 254 on the right.

LT fuel trim was 108 on the left and 16 on the right,

The o2's were at 600 on the left and 54 on the right!!! thats when it threw a SES light.

IAC is at 160

If you try to rev the hell out of it, the numbers equal out some, the longer it sits there and idles the more out of whack they get.

I checked the spark, it's hardly there at all. The spark is real weak, but if you can coax the rpms up it will get brighter, and everytime it backfires the spark goes out completely. This was on cylinder #3. I put a noid light on to check the injector and I am getting an injector pulse. The higher I rev it the brighter the light gets.

When I was driving it home I noticed no matter how much gas I gave it the TPS really didn't show any movement. Once I got it home it looks ok, but driving it when it was running bad it didn't move much.

I went out and checked the spark and injector pulse now that the car is cooled off, WOW what a difference. The injector pulse is really bright and the spark is steady and bright like it's suppose to be. When it gets warm things go to hell.

 

19-20 around town!? how did u get that good of gas milage?
I have a stock LT1 with flowmaster exhaust and a CAI with K&N filter and I was told that I'd be lucky to get 14-15 hwy.

 

I hear that! Its the right bank on my 93z as well, very similar situation, i dont have the time to play around with it right now

 

Any idea's speedy?

 

Well you can go with troubleshooting and repairing what you know is bad. So far as memory serves, (I'm not reading all the back posts) you have a MAP voltage problem and you said you have a drain on the battery.

You can sit and data log every sensor

Or you can keep trying things (and beating your head against the wall) like unplug an O2 and see what it does in open loop

Or you can start from scratch by checking basics first and then test sensors.

A battery drain problem is easy to find. I also mentioned how to diagnose the MAP issue.

How do you want to proceed?

 

have you taken a look in the opti yet? all the complaints sound like what i've seen on a few lt1's i've worked on.


also, it was mentioned fuel trim values way high. 250s or somthing..

I thought these were limited in the PCM, say max trim of 160, min 90 etc.


maybe it was Integater, not BLM.