lectrcsprx

Ok... I upgraded my 85 vette by ripping out all the old stuff. Putting in a new 383 stroker with a TPI mini ram. Had CPU upgraded for motor. I removed all catalytic converters and put in a 4" exhaust with Borla exhaust system. Problem I'm having is cold start she doesn't pop over right away(tested fuel pump and its at 44lbs psi). When warm and going down the road, if I get on the gas, sometimes she bucks and kicks before going like gas is not moving thru correctly. I'm lost guys, I am open to any suggestions on making performance better.

aklim

Who upgraded the CPU? Was it an off shelf program or someone did a "guess a tune" or was it a dyno tune?

What injectors were used? Assuming the motor is sound, have you done a fuel pressure check? I would take the hose off the FPR, cap off the nipple and do a WOT run and see if the pump will keep up.

lectrcsprx

It was done by TPIS up in Minnesota. TPIS sold us mini ram and did the chip. I had a mechanic do a fuel pressure check. We couldnt figure it out. I am considering taking her in to be dyno tuned. I just wanted to make sure I havent missed something. Shes just a tune away I think from ripping it up.

aklim

What is your location? Should put that in the profile so we can see it and tell you where to go. In my case, they will tell me to go to hell.

This is where I got my work done.

383vett

Hope you figure it out. Do you really have a 4" exhaust system or 4" tips?

blackozvet

the elephant in the room is . . . the fuel pump !
what pump do you have in it ?

fuel pressure and volume flow are not the same thing.

aklim

Agreed which is why I suggested a simulated WOT by removing the hose and doing a WOT run measuring the pressure.

bjankuski

It is probably a tune issue (Check the basics like fuel pressure), it sounds to me like you need more cranking fuel for the cold start issue. For the acceleration bucking issue it probably needs more acceleration fuel. Mini rams need a lot more acceleration fuel when compared to the TPI and most tunes do not provide enough acceleration fuel. (This is similar to the accelerator pump on a carb)

lectrcsprx

I live outside Chicago near Elgin, IL.

aklim

I'd put it in the profile so nobody has to ask in future. I don't know but I lived in Madison and trailered it to Hitech. I have also driven there to trade in a Yukon XL for a 7.3 Powerstroke Excursion

lectrcsprx

I can only assume its the stock fuel pump sold by Ecklers.

aklim

Did YOU replace personally? IF not, we don't know what they did. Was the pulsator removed? It can cause issues. Kinda why I think you need to do a WOT run

lectrcsprx

I myself am not a mechanic but helped my friend who is a mechanic do the engine upgrade.. I tinker here n there. My mechanic is a friend and ill relay your questions to him. So run a WOT test. Anything else(I'm praying your not going to say I need to drop the tank)?? I do have a Dyno test place not far from me. Would that help at this point?

aklim

IF we see the fuel pressure keeps up, we can look elsewhere but if you shut off the engine and the fuel pressure rapidly falls or the pump has too many "fall on it's face" moments during WOT, we look at fuel.

You can drop the tank if you so desire but it isn't necessary to do that to get to the pump. Your call.

I wouldn't until we know for sure what the problem is and is fixed. It might be expensive to do there.

vader86

Fuel pump/pressure issue check first, as mentioned. Check at idle, bring the engine speed up and note behavior of the pressure. Kill the motor, see what it does then. Does it hold steady, how long, if not, how fast does it drop? This will point to pump, regulator, injectors depending.

2nd thing is the ECM/chip that was done. It needs to be tuned on a dynojet with a Wideband sensor, that will show the issue with the tune.

Either way it sounds like a not-enough fueling problem.

aklim

Spring is around the corner. Winter specials are over. The facilities might be more busy and charge him for the diagnostic and time to take it off and on the dyno. Kinda why I am thinking he should fix it before asking for their help since they may be more expensive. Your thoughts?

blackozvet

as aklim and vader have said, you need to know things and check things before people on here can diagnose things.
what size are the injectors ? what is the fuel pump ? what size throttle body ? What is the actual fuel pressure ?

taking a wild punt I would say that a stock flow fuel pump on a 383 with a miniram just aint gonna cut it when you get on the gas !

aklim

Hard to say. It might be on the ragged edge, it might not be. Wish he would do a WOT run so we can see for sure.

slhawkins

I feel it's worth reiterating this since it might be tempting to wait to check the pump as a last resort without knowing it.

The fuel pump in our cars comes out in about 15 minutes. Open the gas door and remove the 4 torx screws, the door will then pull away with ease. If it's not clean, clean up the rubber area around the neck and remove the cap. Then carefully pry out the rubber. Remove the hoses and the 9 or so bolts, then the pump will lift right up. It'll take you 15 minutes to pull it out, maybe 30 if the hoses don't come off easy. So whatever you do, don't wait until the very end to check on the pump. :-D That said, I don't see why even a stock pump would have an issue supplying fuel to start the car. Though it could cause the other issues...

It might be worth finding out what base .bin they used for your chip. I had cold start issues once I removed the cold start injector on my 87. In theory TPIS knows about that and would have corrected for it though. Do you have any notes or receipts on what they did for the ECM?

*+1 on the WOT run

lectrcsprx

4" from headers back.