94z not running right.

**t-rock** · 03-17-2008, 07:42 PM

My son bought his car about two months ago with 125k on it. He has put probably 2k on it with no problems. sunday we were driving down the road 40 mph and the motor starts to stumble so as i drive it i realize that the stumble is at very low rpm's and you can accelerate and it cleans up and pulls clean and smooth but low rpm's its rough and and you can hear it pop back thruogh the throttle body or atleast thats what it sounded like. its really weird because in park it tachs up just fine so today i looked for anything out of place and made sure the plug wires were on good so maybe you guru's can give me some ideas. thanks..

**chuckie669** · 03-17-2008, 07:44 PM

I might try to replace the fuel filter first and go from there.

**t-rock** · 03-17-2008, 08:09 PM

that crossed my mind but for it to pop and sputter is almost more like its loading up than a starving problem.

**FUELS94** · 03-17-2008, 09:48 PM

You said you check if the plug wires are on, but if those are the OEM wires they could have crack in them that is grounding out the wire?

**BlackLT1Z28** · 03-18-2008, 05:21 AM

Sounds like the optispark. Mine behaved similarly when it went out. It would have problems within a certain rpm range, but accelerating would make it go away, at least temporarily.

**Sleeper101** · 03-18-2008, 01:57 PM

I think its def something in the spark area, Start with Plugs and Plug wires.

**t-rock** · 03-18-2008, 02:36 PM

[QUOTE=BlackLT1Z28;1372251]Sounds like the optispark. Mine behaved similarly when it went out. It would have problems within a certain rpm range, but accelerating would make it go away, at least temporarily.[/QUOTE

yes thats exactly how it acted. how long did it last before it went out? did you drive till it went out?

**t-rock** · 03-19-2008, 04:45 AM

Oh, and it has not triggered a check engine light yet.

**BlackLT1Z28** · 03-19-2008, 10:43 AM

No, I put a new one in before I gave it a change to go out. My mechanic said that with the miss-fire, there was a possibility of burning a hole in the piston or something. So I didn't chance it and changed it out. It will get worse the more you drive it. My advice, once you know it is the opti, change it out. But go ahead and do the plugs and wires first just to be sure.

**96slow6** · 03-19-2008, 11:35 AM

That is alot of money and work for something that you dont know for sure it the problem. It was mentioned a few posts up. Change the fuel filter first. Then clean the MAF sensor with electrowash and some q tips. Be carefull not to break the resistor wires. If these don't fix it then get the car hot at night and look for arching at idle. You will see little arches. Look closely it can be hard to see. If you have no arching, then I would look at the opti or o2 sensors. This should give you a few things to look at. Always do free to cheap stuff first. A bottom end stumble is very rarely a Opti issue. You get more of a top end stumble and a low/high res DTC along with it. Low end stumble is more of a fuel and o2 problem.

**fojtik83** · 03-19-2008, 01:58 PM

more than likely it is a plug wire arcing off or your plugs are gapped and need to be replaced don't over look those two. and those will cause the car to all the sudden do what you described.

**BlackLT1Z28** · 03-19-2008, 02:59 PM

My opti showed trouble during light acceleration from ~2K-3K rpms, I wouldn't call that top end at all.

And if it was an O2, it would most likely through a code.

**LT1ricekill** · 03-19-2008, 03:59 PM

hey whats up i got a 94 too and it has the exact same problem i looked at my engine and one of the wires has a crack in it from the header and i think thats it hopefully i am putting new wires and plugs on it this weekend so i hope it fixs it cause i kno how u feel i cant even drive my car it wont really go any where

**t-rock** · 03-19-2008, 04:11 PM

Well guys i drove the car for 30 min after replacing the fuel filter my son picked up a wix and thats what was on it already the car is driving like a champ with only 30 min behind the wheel. So far so good we will keep a close eye for the next couple of days and will keep you guys posted. Funny thing is i blew threw the old filter with little to no resistance so im not totally convinced the problem is solved yet. so thank you so much for all your help!

**neto06** · 03-20-2008, 04:04 PM

hey i was jus wonderin if you knew if there was any big difference between 95 and 93 z28

**96slow6** · 03-21-2008, 07:10 AM

In a couple days let us know. Always go simple first.

To neto06 there is alot of difference between 95 and 93. 93 has a ECM not a PCM. 93 is a SD car not a MAF equiped car. It also has a different fuel rail. 22lb injectors not 24. The trany is not computer controled. 95 has a vented opti I am pretty sure. The 95 opti uses a dowle pin to drive the opti not a splined shaft. What specificly are you looking for?

**t-rock** · 03-22-2008, 09:01 PM

well its been a few days and he has about 1 hr of driving it. im glad it wasnt something major yet. the seller told me that the intake gasket had just been replaced i hear thats common with these motors, is that right? and seeing that it was just replaced should i see if any bolts need to be tightened?