Ok the car was running fine today and then the tack started to bounce from about 800-1000, and the car ran like ****. And then the car started to miss pretty bad. the car starts but does not idel right. Then if I drive it it will accelerate (but lacks some power) untill I reach a constant speed and then it brakes up pretty bad untill I get deeper into the gas, and then the same thing at a constant speed it brakes up agin.

I bypassed the electronic ignition box and ran off the oppti with the same result. When I first started it up it ran fine and when it went into closed loop it started missing.

Also I scanned the engin and tranny and found no codes?

Aweek or to ago I had a problem with the idel surging. I scanned it and found the tps code I cleared it and it ran fine till today? Could it be the tps, but I am getting no code or mill light.

Any hellp will be greatly appriciated!

 

I dont know if his has anything to do with it or not but when I turn the key on in the run position the fuel pressure gage reads about 44 psi and when the fuel pump kicks off the pressure immediatly bleeds off. Could this cause the miss. Could the injectors be leaking or is there an other common problem? I also removed the evap can and left the line back at the tank just hang open, is this the problem. And the car is running rich.

 

Your fuel pressure should stay in the line for a while. If you have a leaky injector it should show on your plugs. You could have aline leaking letting in air or a bad regulator.

 

I puilled the fuel rail and turned the key and had no leaking injectors. Could the evap line that I left open be the problem?

 

My evap line has been disconnected for 4 years with no problem. With the car running tap on each injector and see if it makes a difference. Do the same with the regulator. I did have a problem with a pump leaking in the tank. The pressure would build and leak right back down. The hose between the pump and hanger was leaking.

 

It is the distributor cap,I had the same problem with my 95 T/A.Tach jumping,etc.I installed a complete distributor,because at that time GM did not have the cap and rotor seperate.
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Also does the problem happen after the engine warms up and then gets worse.

 

yes it runs fine untill warm or closed loop and then just gets worse.

 

I drove around with a scanner hooked up tonight and found out that it runs fine untill closed loop. What all goes online when closed loop hits? I unplugged the oxygen sensors so the car would stay in open loop and it runs fine. Are the oxygen sensors the only thing that comes in at closed loop?

 

I believe the EGR has some funcion with closed loop and automatic shift points. I vaguely remember something about the MAS as well. Try diving it with the O2 sensors plugged up and the MAS unplugged.

 

Are u reffering to the mass air as MAS? and the egr was removed and programed out.

 

MAS is Mass Air Sensor. This should put the car in speed density mode. If the car runs better with it unplugged it may be bad. I had one go bad and hot throw a code. Also make sure you have ignition voltage at the pink wire on the O2 sensors. Check out this post. Car is running bad once it warms up. Need Help! - CamaroZ28.Com Message Board

 

a friend of mine has had a few problems like this before.. once an o2 wire was burning on a header.. the other was the ignition module was going bad.. That ignition module is bolted to a braket right to the head along with the coil and maybe it could be getting heat soaked.. Just another theory.. but its worth taking it off real quick and running it to the zone to have checked, so you can rule it out if its not bad. I posted the same thing in that z28.com thread, so i hope i help someone get closer to fixing their problems.

 

If the ignition module was bad it wouldn't run good then start missing when in closed loop mode. I have heard of O2 sensors making one miss, when I had a wire get burned into, it just threw a code and that was it. If you unplug the MAF it will throw it into open loop again and probably will run fine since it will throw a SES for the MAF being faulty. I would start with O2 sensors since they are cheaper than a MAF.

 

I think that I am going to get o2 simulators, and see what happens. I bench tested them a week or two ago and they seemed fine but now the scanner is showing: left bank~600 (and changes)
right bank~1290(pretty steedy)

I extended them my self, and for anyone who has ever done this those alumium wires or what ever they are suck to solder. And I wraped them with loom and then heat wraped them.

 

There are no simulators for the primary sensors. Simularors are for the rear sensors on OBD2. You need the front ones. I haven't hears of anyone that didn't have trouble with O2s after extending them. You are going to need to get new O2s and if you extend anything it should be the engine harness. Another option is O2 extentions.

 

It is reading that high because it is misfiring,(raw fuel).

 

i was having the same thing. i havd to change 2 of the injectors. what do the plugs look like???? if you only have a few plugs that are black, change the injectors to diff cylindes and see if the foul follows, thats how i figures out mine was the injectors. i did the same thing took the fuel rail off can cked with the pump but nothing. just my 2 cents.