Ar0ck

I don't know how to explain this better then once my car is warmed up it will not rev past 2,500+ RPM's while driving. When the car idles its completely fine. It happens in all gears and at all speeds in the RPM range above 2,500. I took a video if it to help people who haven't seen my car. If the car is still cold I can run it to red line without any problems but maybe a few more minutes down the road it becomes intolerable to drive.

The car is a 1995 Z28 M6 with a CC306 and worked heads, & s stock short-block. I am currently running stock 24# injectors with a newly installed Racetronix 255 fuel pump. I have Racetronix 38# injectors but I'm waiting to install them until i hear back on cost to have the computer re-tuned by MadZ28. I have this feeling that its fuel or tune related because I figure if it was ignition I would notice it even at idle. I plan on performing a basic tune up next weekend. Does anyone have any suggestions?

my94blackz

Sounds like a coil, any codes?

This is what mine done with a failing opti, it done fine for the first 20~ mins cold then well lokk for yourself. https://ls1tech.com/forums/lt1-lt4-modifications/560422-i-am-tired-crap-vids-inside.html

goodrich969

iTrader: (9)

yeah check the ignition and the opti.

Hot94Z28

If it dont do it till it warms up might try and unpluging the 02's? Make it run in open loop see if it helps.

burnzilla

iTrader: (3)

Optispark.

I had one go in my friends Z28 and it did the same thing.
It would run ok, then at about 1800-2200 rpms it would stutter and skip.

If he floored the car it seemed to rev ok but I could tell it was still having trouble.
I told him to stop driving the car and fix it ASAP, he didnt and he ended up blowing the ring on his #7 Piston.
Im not 100% sure its the opti, just like anyone else here, but its from hearing youre car is definitely electrical.
Car sounds good, fix the problem now before it gets any worse.
And when/if you get a new opti, make sure to get a vented one.
Good luck... ( car sounds nice! I'd hate to see you throw a ring )

speed_demon24

iTrader: (6)

Unplug the 02's and reset the computer and see if its any better. If you just unplug the 02's without resetting the computer it won't tell you anything since it's still going off the stored values from the 02's.

Ar0ck

I'm no expert but wouldn't I notice ignition problems at idle? I can rev just fine at idle.

I'm beginning to think its tune related.

burnzilla

iTrader: (3)

Funny you say that, because the car I mentioned would only skip under load. (or, going down the road)

IllusionalTA

iTrader: (9)

if you were to go wot and it cleared up. then it would be 02's.. What you have sounds like a opti/ignition issue.. when you free rev there is no load as you know on the motor. i.e diff timing map's.. so when you put a load on it.. the timing requirements are different therefore letting this problem arise.. coil's can act up as well after they heat up...

Ar0ck

I talked to Ion Soltan of MadZ28 who did the tune on my 95 heads & cam Z28. I told him about the problems I have been having with my car breaking up under load, and he said:


Quote:
This looks more like a plugged cat or an ignition issue, if it's doing this on the 24s. If it's doing this on the 24s specifically after the fuel pump install, you will need an adjustable fuel regulator and set the fuel pressure at 43.5. I still think you have other issues, most likely ignition related.

I obviously ruled out the plugged cat problem since I don't have any cats to begin with.

Currently my ignition consists of a MSD Blaster Coil, Opti Summit, Taylor 8.8mm plugs & NGK TR55 plugs (not sure of the gap). I'm going to tackle these issues this week and try swapping out parts mainly the blaster coil. I'm going to wait before I send out the computer again untill I have checked the ignition over. I've had this issue for a few months even back when i first did the heads & cam with the same ignition set up.


Now back to my main issue... a fuel pressure regulator. What exactly does it do, where does it go, how difficult is the install, will I see gains, and is 43.5 sound right?

IllusionalTA

iTrader: (9)

MSD Blasters' SUCK!! Go w/ a accel coil.. or stock.. Granted these are my opinion's.. but i haven't had any luck w/ msd coil's in anything from my t/a to my buddies neon...

WhyHelloOfficer

iTrader: (5)

Firstly -- get a dyno tune. Yes a mailorder tune can get you in the ballpark, but with the money for shipping, re-tuning, and the downtime waiting for a new tune, you could get one dyno tune that is spot on the first time. I had a mailorder tune that was leaning me out way too bad up top (almost 14.0) -- and I'm running a very common off the shelf cam.

What is your fuel pressure currently?

Pull your plugs and see if they show signs of running either lean or rich.

How new are your plug wires? Are you positive that none of them are burned/cracked/not in proper operating condition? Start the car at night without any lights on, and look to see if any of the plug wires are arching -- Personally I've had bad luck with Taylor wires in the past, and I've heard of other horror stories with them as well. I'm not saying they are your problem, but I'd bet a new set of wires would help.

How new are your O2 sensors? What brand are they?

Do some trouble shooting before you just start randomly throwing parts at the car. You'll save yourself money in the long run (and a whole lot less of a headache).

Ar0ck

Its very hard to get a Dyno tune in my area. I have to travel real far to places that I have no experience with.

I have to still get a Fuel pressure gauge on the car before i find out my pressure.

The spark plugs are definitely a little black for running rich, but I guess that would be suspected for having possibly bad timing.

The plug wires are new since October when i first got the car running, then I spun a bearing in the old motor a month later so re-used them. I checked under the car today and all the wires are fine, no visible burn marks or cracks and they are very well distanced from the headers and other major heat sources.

The 02 Sensors are brand new Delco ones from October.

Tonight I swapped my MSD Blaster Coil for a stocker from a friends car and checked for arching and nothing showed up as being unusual but the problem still exists.

I haven't driven this car WOT since late August. Its becoming a real hassle to keep on top of.

Chevy053

[QUOTE=Alex @ QTP]Its very hard to get a Dyno tune in my area. I have to travel real far to places that I have no experience with.
QUOTE]

Isnt TTP Performance near you?

Im not sure if they tune LT1's though.

BizZzatch350

iTrader: (33)

Have you checked the Ignition Control Module? You mention it got hot when it starts doing it, theres a quick mod you can do to space it, i provided a link below.

http://shbox.com/1/4th_gen_tech2.html#ICM_cooling

Ar0ck

No unfortunately they do not tune Lt1's.

I'll try that Tomorrow @ lunch. Sounds easy enough.

69gto96z

iTrader: (13)

Do you have cats on it? My buddies vette did the same thing with some clogged cats. Nevermind, I just read above and noticed u dont have cats

Ar0ck

Just incase:
Engine:
-Comp Cams CC306 (230/244 .544/.576 112 lsa)
-Comp Magnum 1.52RR
-Comp .0072 Chromemoly Push-Rods
-Comp 977 spring
-Comp Ti +.050 retainers/seats/locks
-ARP 7/16 studs
-561 casting heads flowed @ 255cfm @ .500 lift
*54cc Chambers
-ARP Head Bolts
-Racetronix 255lbhr Fuel Pump & Hot-Wire kit
-Stock 24# Injectors (Have Racetronix 38's waiting)
-GMPP HV Oil-Pump
-Lunati Double Roller Timing Chain
-Port Matched LT1 Intake with Ported Runners
-GMPP EGR Block-Off plates
-Enlarged Throttle Body Opening (sized for 58mm throttle body)
-Stock ported Throttle Body
-K&N FIPK2 Cold Air Intake
-Trick-Flow Hard Intake Elbow
-Rk Sport Air-Foil
-March Under-Drive Pulleys (Crank & Alt)
-Summit Opti
-MSD Blaster Pack
-Taylor 8mm Thunderbolt Wires
-NGKTR55 Spark Plugs
-160* Thermostat
-Meizer Electric Water Pump
-!A/C 1LE A/C Delete Pulley
-!AIR/EGR
-Throttle Body ByPass
-MADZ28 Tune

Exhaust:
Pacesetter 1 3/4 Long Tube headers
Pacesetter Off-Road Y-pipe
-Magnaflow 3" Cat-Back Exhaust
-QTP 3" Electric Cut-Out

BizZzatch350

iTrader: (33)

Good luck with it Alex

WhyHelloOfficer

iTrader: (5)

Something to check out:

Making sure you're getting a signal to the ignition coil
http://shbox.com/1/4th_gen_tech2.html#opti_test