Rij1

I have a 94 z28 6 speed and I've been trying to figure out what the problem is. The car has only about 2/3 the power now but had more when I bought it about 2 weeks ago. I've replaced the fuel filter, air cleaner, spark plug wires. The spark plugs are about a mouth old. I've adjusted the valves zero lash while running because a couple were ticking. I did a compression test and there all between 200-205 psi. I readjusted the spark plug also cause they were off. The car seems to be gasping for air or somthing and chatters a bit off the line and through the gears. I doesnt have much power till around 2500 rpm's. I've already gapped the plugs from 0.056 to 0.050 and back to 0.056 where they were when I first pulled them. what could be the problem? also, I was driving on the freeway and in sixth gear it had good passing power and now it doesnt. I barley passes and It doesnt burn out anymore either. I started to check things out and un plug things to see if it made a difference to idle and how it drove. I unpluged the maf sensor and the car almost died and then ran like it did before i unpluged it. I drove it like that and it still ran crapy. I unpluged and pluged in all the injector wire one at a time to see if it changed any thing, They all did. I did have it scanned and there were no codes. also the map sensor that didnt make a difference in anything..

bw_hunter

The first thing I'd do is check the plug wires. cross a pair and things go down hill fast...

Injuneer

Have you scanned if for codes? Have you checked the fuel pressure?

I think you would get better result if you stuck with a single thread on the topic, adding new info as you go along. Posting multiple topics that all appear to be related, or may be related even if they don't appear so, usually does not produce good results.

https://www.camaroz28.com/forums/sho...d.php?t=829005

https://www.camaroz28.com/forums/sho...d.php?t=828744

https://www.camaroz28.com/forums/sho...d.php?t=828850

https://www.camaroz28.com/forums/sho...d.php?t=828848

Rij1

I just checked the wires and they are right, I scaned it and It didnt read any codes. I havent checked the fuel pressure but it ran real good before I did a tune up. within a week ago.

Injuneer

How did you scan it?

Rij1

I took it to a shop and they hooked it up to there scaner and didnt find any codes on it. I just drove it for about 2 hours and it feels like if I give it gas below 2500 rpm's its power dies down but if I barely give it gas it seems ok but It barely accelerates. If I give half throttle it takes a while to catch up to its self.

Shaun 95 camaro

I dont know how your exhaust is set up but I know when my cat. conv. had a melt down the car ran like crap and the exhaust had a muffled sound to it. Just something to check.

Final03

Have you checked to see if your getting good spark there is a huge diff. between spark and good spark ... Are all of your cylinders firing... Do you hear any misfiring... when you adjusted down to zero lash did you do it correctly?
Do you hear any type of air under the hood like a vac. leak that can cause this easily.. A hose could have got a hole your prob. is a very general one so therefore there are so many things that can cause it best thing is to do is go over everything peice and part by part slowly. don't rush as you will over look it 100 times before you find it if you rush.

Rij1

that kind of explaines why the car sounds soo different now, I'll have to check the cat on it but it's new and been welded so i'll have have someone cut it off and sut up a bolt on cat. I know the car is still missfiring and I'll have to change the coil to be sure its getting the proper spark but I dont know if I should get a coil that puts out more power or just stick to a stock one. I'm pretty sure I did the zero lash correct. I looked it up on a few different sites including shbox.com . I'm sure all the cylinders are firing but I'm going to check again.

Injuneer

You check the cat by having an exhaust shop put a pressure gauge on the O2 sensor bung, and checking for excessive back-pressure.

my1994z28

I would check the wires make sure they are seated all the way,and are in the correct order.What kind of plugs are you using?I know you said the catilitic converter was new,how long ago was it put on?What was the fuel pressure at?

Rij1

I checked the wires a few times, I;m using ac delco platinum. as for the cat I think its about 6mo-1yr old. I still havent got around to checking the fuel pressure yet but am going to get to it asap.

firstz28maro

Mine was doing the same thing. Change out your opti.
Bog down under load at 2000RPM. Get above that and take off again.
Check your water pump rear seal make sure it good too. Ended up changing
out my pump as well.

Rij1

If i'm going to change that would I need to change the opti distributor or just the cap and rotor?

Rij1

OK, I have had my car in the shop for a week getting a dianostic check. so far there arent any trouble codes, and he says its not missfiring. he says the cats are good and the o2 sensors are also. the fuel pressure is in good stats too. he says he cant find anything wronge with the car. So now he's going to check the fuel injectors and the maf sensor. If the opti is giving the problem cause of moisture in it will it miss or can it give a problem that i'm having and not show that it is miss-firing?. He also told me the car is running rich.