[MetallicAvet]

OK I have been officially vette less for 6 months and I have to tell you that its been driving me insane!! I dropped alot of money in my car by doing alot of upgrades. I went to this place in van nuys ca called strictly performance where they supposedly specialize in fbodies and vettes. I dropped in 3.73's 30lb injectors with the miniram intake, 58mm tb, fuel pressure reg., msd 6 ignition and coil and wires, port and polished edelbrock performer heads, custom grind hydraulic roller cam with a 550 lift, converted to speed density, custom chip, msd fuel pump in conjunction with the factory in-tank fuel pump etc. my motor was already stroked to a 383 prior to this. The problem is that the shop cant figure out why its not running right i mean, everytime i drive it on the highway slowely and progressively it starts to sputter and then at times it feels it wants to shut off, when i give it more gas the rpms just drop and it feels like the engine just shuts off, then when i let go of the pedal it sparks back up temporarily then it turns off on me on the highway. I have replaced the distributor, spark plugs, they messed with the timing we are just stumped and have no idea where to go bottom line my car runs rough when it wants to and at highway speeds it progressively runs rougher and rougher then it starts to act up as i stated earlier in the post. What could it be:down: PLEASE HELP ANYONE!

THANK YOU, TONY

 

[MetallicAvet]

few more things, i also have a custom torque converter with a 2800 stall and i have no codes showing, "no service engine soon" light on, new alternator old optima battery, thanks

 

[The Torch]

The first place I'd start is fuel delivery, 30#'ers are going to be using it. What pressure is your pump putting out. You could install a pressure gauge (outside the cabin) and see what it does when you are driving. You could be starving for gas

 

[The Punisher]

What exhaust are you running. Stock? aftermarket Cat? STill have pre-cats installed?

 

[OldVetteFan]

Does the shop have a laptop with data logger software? You need to get some real time data to show "good" vs "bad".

I think Torch is also on the right track - it sounds like a fuel delivery issue.

Steven

 

[Joe B]

Does the shop have a laptop with data logger software? You need to get some real time data to show "good" vs "bad".

I think Torch is also on the right track - it sounds like a fuel delivery issue.

Steven

I agree 100%......without getting some good hands on dyno tuning with a data logger connected and a wideband 02 in place....it will always be guesswork to get it just right.......also, like mentioned with a "possible" fuel delivery issue which it "easily" could be....first of all (if you haven't already) make sure you put a brand new fuel filter on .....then make sure you have adaquate fuel pressure and VERY importantly "fuel flow".....you can measure the flow with a timer and a bucket for the fuel to be pumped into.......if all this checks out ok....then (like mentioned by Torch) the fuel pressure needs to be checked while under load(while driving) to see if the pressure does anything suspicious........Joe:thumbsup:

 

[boynton6spd]

Fuel pump/filter

 

[MetallicAvet]

I believe its at 60 psi of fuel pressure, i have 2 fuel pumps, an inline fuel pump and a in-tank fuel pump both are working simultaneously, we are STUMPED like i said sometimes it feels good and strong BUT once i get on the highway that is where the problems begin, power loss, sputtering, backfire and eventually it dies at high rpm

ANYONE???

THANK YOU:lookinup:

 

[MetallicAvet]

BTW, im running straight 3'' pipes and headers no cats

thanks!

 

[MetallicAvet]

any opinions GRUMPY??:lookinup:

 

[driley]

I say go back to basics. Sounds like the distributor might be off a tooth. I'd check there first. Not the first time it has happened. It will run a tooth off, just not good. If it is back a tooth, the shop probably has it advanced all the way to idle, but at highway speeds when it needs the advance, it is already maxed out. Even though the light is not coming on, check for a code that represents cylinder misfire.

 

[-=Jeff=-]

I say go back to basics. Sounds like the distributor might be off a tooth. I'd check there first. Not the first time it has happened. It will run a tooth off, just not good. If it is back a tooth, the shop probably has it advanced all the way to idle, but at highway speeds when it needs the advance, it is already maxed out. Even though the light is not coming on, check for a code that represents cylinder misfire.

if the distributor is 'off a tooth' all you need to do is twist the body of the distributor and you are fine..

Also he will not have a code for cylinder misfire.. I am guessing he id OBD 1


Now here are some questions for the OP:

1) 60 PSI ?!?!? why so high

2) what RPM is the motor built to spin to? I don't honestly think you NEED dual pumps, I spin my motor to 6200rpm, with 30# injectors and ONe 255lph pump.

3) I doubt you are starving fuel, my guess is flooding it.

4) you said the car is converted to Speed Density, what ECM is it using now, how was it tuned?

5) which brand injector are you using, a 30# SVO (ford) is 30# at like 42psi..

I think you definitely have a fueling problem, I think you have too much fuel.

My combo: ZZ9 Cam, CNC Heads, Miniram and 350 CI I run 30# injectors but they are OVERKILL, but I tuned them to run nicely, but I also run 48psi at WOT.

If it were me I would get my hands on a datalogger to SEE what it does, then start changing things. but I still think the 60 psi is a bit high 50 would be better and then retune from there.

 

[driley]

if the distributor is 'off a tooth' all you need to do is twist the body of the distributor and you are fine..

Also he will not have a code for cylinder misfire.. I am guessing he id OBD 1


Now here are some questions for the OP:

1) 60 PSI ?!?!? why so high

2) what RPM is the motor built to spin to? I don't honestly think you NEED dual pumps, I spin my motor to 6200rpm, with 30# injectors and ONe 255lph pump.

3) I doubt you are starving fuel, my guess is flooding it.

4) you said the car is converted to Speed Density, what ECM is it using now, how was it tuned?

5) which brand injector are you using, a 30# SVO (ford) is 30# at like 42psi..

I think you definitely have a fueling problem, I think you have too much fuel.

My combo: ZZ9 Cam, CNC Heads, Miniram and 350 CI I run 30# injectors but they are OVERKILL, but I tuned them to run nicely, but I also run 48psi at WOT.

If it were me I would get my hands on a datalogger to SEE what it does, then start changing things. but I still think the 60 psi is a bit high 50 would be better and then retune from there.

On the OBD I, it will set a code 42 if it is off as far as a tooth but won't turn on the light. I just fixed this problem on my friends 1985. A supposed reputable shop intalled a 383 GM crate motor in his car, and it would barely idle. Would run decent midrange and fell on its face if you tromped on it. The distributor was advanced too far. I know that you can compensate by turning the distributor, I was just suggesting he check it. I do agree he has way too much fuel pressure at the rail, but unless it is causing the injectors to leak, the computer is still controlling the pulse of the injectors. I run 30# injectors in mine, with about 42 psi at the rail. I have a custom chip from Motorvation that has been tuned for the injectors. I have no drivability problems, and my car runs great. I drive it 800 miles round trip every year for a car show in West Virginia and last year got 30 miles to the gallon on the highway. I've never had my car on dyno but I Know it definately runs better than it did from the factory, and it will smoke the tires all the way down the block.By the way, the timing on a GM 383 is 10 degrees BTC at 900 RPMS with the advance unplugged.

 

[-=Jeff=-]

I do agree he has way too much fuel pressure at the rail, but unless it is causing the injectors to leak, the computer is still controlling the pulse of the injectors. I run 30# injectors in mine, with about 42 psi at the rail. I have a custom chip from Motorvation that has been tuned for the injectors.

This is the key, and I have a feeling this is where some if not most of the problem is

 

[MetallicAvet]

thanks guys for your help, we are starting with the basics and I will keep you guys posted THANK YOU!!