having a problem with a 97 Z...
only mods are filter...loudmouth..o2 sims...and no cats
the car had the problem prior to all of these mods

For some reason, when the car gets WARM, and only when it is warm, It has a nasty stumble. When it is cold..it pulls hard with no stumble all the way to 6k rpm. When it gets warm, it has a real bad stumble. Can't figure it out. The only codes i have gotten are for the 02's and cats. Now i have no cats and the 02's were swapped with supposedly known good ones. The only thing i can think of is that they were bad. What else could it be?

Problem number 2...the car starts real hard. It cranks and cranks before it finally fires, but it only does it when it is cold. WHen it is warm it fires right up.

 

I am having the same problem, so far plugs and wires were replaced, and the problem is still there. I have to check the O2 sensors, but i get no codes in datamaster. Have you checked your plugs and wires?

 

i did not change the wires but the plugs have been replaced

 

Check your fuel pressure when you shut the car down. It is probably dropping fast when power is cut. Chances are good that one or more of the injectors is leaking. When the car sits, fuel puddles in the intake and takes a while to burn off when you start. The other posibility is the fuel pump check ball is bad and lets fuel run back toward the tank. However, this would not account for poor running once hot. Probably the injector leaking does not become a problem until warm since the engine is richened up when cold during open loop anyway.

To confirm the injector, remove the bolts in the fuel rail and lift it up with all the nozzles of the injectors visible. Prime the pump and see if any are dripping.

 

i'll try that out..i'll be getting a pump and injectors before long anyway..so i'll look into that.

Anyone on the nasty stumble?

 

anyone?

 

..you said you changed the plugs...make sure your plug boots are on all the way and see if any of your plugs have backed out. Did you gap them all correctly? And which 02's did you change? Front or back? You have simms in the back...but is that because you were throwing codes? If you did the fronts..Maybe swap the other ones back in and see if it makes a difference...well thats what I would be checking out.

 

checked everthing but the rear o2's. I knew there were probably junk, so i went ahead and stuck sims in there. I may have to replace the front ones again. The wire boots were all on nice and snug.