I have a 95 z28 and im having a bit of trouble....a few weeks ago it started acting up wit a hestitation/stumble and i was wondering if since i changed plugs, wires, egr valve, ign coil, injectors etc.....i have a 150 k miles on the car and its bone stock.....a few days ago it was running very rough and died...when i started it back up it acted the same way.....i tried starting it after an hour or so and it would turn over but wouldnt start....opti?????????? im thinkin so since i have never changed it out since the car was new....any ideas??

 

Sounds like everything has been replaced except for the opti!!

 

Replace your cat(s). 150k = dead cats. Also, O2 sensors will probably need replacing too.

 

Oh of course, new o2 sensors were put in less then a month ago...so maybe the cat needs to be changed out...what about the opti though?? since its have a horrible stumble and hesitation...does the cat have symptoms like this??

 

Opti is possibly the problem. When was your waterpump last changed?

I don't know how or if you can tell a bad cat just by looking at it but I'd find out. Hell you could unbolt your I-pipe and look inside, that'd be easy enough. Anyone back me up on this?

 

A bad cat will restrict your exhaust and make your motor work much harder to push the exhaust out. If it's never been replaced, it's 50k overdue. Definetly replace that before anything else.

 

definetly the opti....IMO. Check for spark, and fuel pressure. But, most likely the opti, my car did the same thing.

 

IF the cat is bad, your exhaust will not be nearly as loud. It will restrict it. Sounds like opti to me.

 

question was never answered.......i was wondering if it was the cat, would that have the same symptoms such as the hesitationa nd horrible stumble problem when it warms up...but i also have a popping backfire when it heats up....pop pop pop!!!!

 

probably wouldnt hurt to replace the cat, but 9 times outta 10 its the opti with the symptons your giving

 

pop pop pop out the exaust time to gut the cat. Look to see if that thing is cherry red if so well thats ya prob. When it starts to do that look at the cat.

 

would the popping be the timmiing is off since my opti is going bad....i was also wondering since my car wont start anymore that its done for sure...

 

the popping would be the timing, the spark plugs, or wires. But if it wont start at all...the opti is done for..check for spark by taking a wire out, putting a spark plug in it, and have someone crank the engine. Hold the end of the plug to the block and look for spark...no spark= a dead opti...most likely

 

Ok so i just checked the opti how you said and im getting a really small spark from the plug when i put it on the block....should it be a big spark or a small blue spark??