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new project 95 z28 m6...

3K views 25 replies 6 participants last post by  BrettLT1 
#1 ·
first time posting on the site. i have expierience with lt1s and camaros and firebirds and stuff...either way im having an issue with this 95 camaro i just bought and was seeking some advise. For uprgrades it seems to have headers and k&n intake... it seems to runs descent at higher speeds(over 40ish), bug chugs aroound a lil bit taking off....changed the plugs and checked wires ok. seems to be getting plenty of gas just feels like a miss...any leads? has been driven in snow(not by me :p)
 
#6 ·
Thanks so much for your response Brett. Yeah I'm expieriencing exactly what you described. I almost wanna blame the optispark, but that's a $350 delco/delphi unit :p. when I changed the spark plugs they smelled like it was burning rich. It was better after but didn't cure the issue. I'm going to change the wires this weekend even though they look okay I'll let you know how it goes...
 
#13 ·
You should do some diagnostics before just changing parts at random – that can get costly (although it's not necessarily a bad idea to have a spare opti laying around). Is there any smoke when it's chugging and if so, what color? Have you scanned for codes? There are some big ones that don't light the CEL.

I would start with the things that are easiest to check, like a code scan and testing the fuel system, then move on to ignition issues and data logging. It's difficult to find a place to scan a '95, so some just buy an OBDI compatible scanner and most use Datamaster and purchase the ALDL cable to be able to connect a laptop. For fuel diagnosis, a fuel pressure gauge is necessary and cheap. Ignition components can be checked with a spark tester and by having the ICM brought to you local parts store (bring it hot) that has an ICM tester.
 
#15 · (Edited)
How did you determine it's running rich? You will usually get a puff of black smoke when you mash it if it's rich. You should also be checking O2 operation and LTFT's in a scanner to verify. Excessively rich conditions will eventually throw a code and light the SEL. A quick check of the vacuum hose at the FPR is a good idea to be sure fuel isn't leaking past the FPR diaphragm and into the vacuum line.
 
#18 ·
got a coule things accomplished yesterday. found that the MAF sensor was on backwards, not sure why or if that makes a huge difference but corrected that. i also had a emssion hose of some kind coming off the intake on the driver side going to towards the brain box, that was broke, replaced the hose and found the right connection.
2 more unresolved issues i also found. i keep smelling gas like its burning rich(unburned gas), so i check the fuel lines, looks janky as hell, but werent leaking, follow it to the fpr, that was leaking at the bottom. i will be replacing that today.
i heard the exhaust spuddering so figured id see what going on. its coming apart where the y-pipe meets the cat, 96000 miles on this car, and i heard the cat making noise, like shakining coins in a coffee can. Is this a bad cat? how will i know for sure?
 
#20 ·
I agree 100% with firehawk! Trust me this guy knows his stuff.
On another note, I too would also suspect the opti spark. If you have the time, You should clean off your ( o2 ) if it is running rich. They could be reading wrong.
Also (did you get a tune with those headers?) I have heard that its good to get a tune with headers.
 
#21 ·
thanks everyone for the advise, i replaced my fpr and ran new fuel lines (old ones were nasty rigged together :p), and it is running soooooo much better.i think 1 line wasnt getting fuel....

On another note, after i replaced everything, i fired it up for the first time and it backfired out the intake : 0 scared me. lots of smoke...
then i fired it up again minutes later and it gradually came to a 900 rpm smooth idle. i test drove it and it is wayyyyyyy better.

Why did it backfire? Was it used to getting limited fuel to run?
 
#23 ·
Is your pump making a whistling/whining noise? Thats usually a first sign of a dying pump, but usually fuel pumps just work fine or quit in most cases....i would check your fuel lines. a common area of leakage is where the steel lines meet the plastic. Look underneath your car under the driver seat, thats where they meet, and thats where i found my leak, plus if you smell it really strong this is a good place to check. .....where do you smell gas? under the hood or while driving?
 
#25 ·
Two things to check. Make sure none of your spark plug wires are touching the headers and check for an exhaust leak pre O2 sensors. The OBD1 cars only have pre cat O2's. So if there is an exhaust leak before them it pulls fresh air in an tells the comp you're running lean.

Good luck. I had both problems. Runs like a top now and gets better gas mileage too.

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