MPFI Upgrade

[Gary Cookc]

My 98 350 vortec with 125k miles has been stinking really rich lately when cold. It gets some better when warmed up. Just want to ast if the mpfi upgrade is the way to go. If so which unit is the best? ACDelco or Sorensen or something else? Will I see a real difference from the old scfi system?
Thanks

 

[delta_p]

If it isn't misfiring then it probably isn't the spider. Usually the poppet either sticks closed or injector remains open both of which should cause the running like crap and a misfire cylinder code. Do a fuel pressure test and monitor the fuel pressure when you shut off engine. If it leaks down quickly, there is a problem with the regulator, injector leaking, leaking spider hose, ect. which cause you to go into the upper intake. If you do that, then get the MPFI.

 

[GoToGuy]

I did the OE Delphi on. 98Tahoe, she said " what did you do?" Made a big diff. My cousin did ACDelco on shop truck, 96 gmc , he called and said " why did i not do it sooner? Basically i think the poopet thing wasn't very well thought out. Doing the upgrade is really installing better, more current technology. You will allways find somebody who hates anything if you look around. I did it, i recommend it. Good luck.

 

[Gary Cookc]

I did the OE Delphi on. 98Tahoe, she said " what did you do?" Made a big diff. My cousin did ACDelco on shop truck, 96 gmc , he called and said " why did i not do it sooner? Basically i think the poopet thing wasn't very well thought out. Doing the upgrade is really installing better, more current technology. You will allways find somebody who hates anything if you look around. I did it, i recommend it. Good luck.

Truck runs good with no codes. Pressure test was good but it smells rich at idle. Thinking about the upgrade but still undecided. Is mpfi brand important?

 

[delta_p]

I put the ACDelco 217-3029 in my '96 350 about 5yrs ago. Based on the price they show for that now ~$500, forget it. I'd put the FJ504 in it.

 

[1997]

I used FJ product for the 97. No complaints, no extra power, but starts and run nicer than the orig.

 

[Schurkey]

My 98 350 vortec with 125k miles has been stinking really rich lately when cold. It gets some better when warmed up. Just want to ast if the mpfi upgrade is the way to go. If so which unit is the best? ACDelco or Sorensen or something else? Will I see a real difference from the old scfi system?
Thanks

You won't gain much with the updated injectors, if the injectors aren't the problem.

When was the last time the O2 sensors were changed? How old are the spark plugs, plug wires, cap and rotor? How old are the air and fuel filters? Is the charcoal canister saturated? Does the PCV system work right? What is your fuel pressure under load? Does the fuel pressure hold when you shut the truck off?

"Stinking" can mean that your catalyst has been poisoned. Maybe it recovers when you fix what's wrong...maybe you replace the catalyst(s).

Connect a scan tool, look at the sensor data, and then look at the output data. Look at the cylinder-by-cylinder misfire counts, and misfire history.

"Codes" can be helpful. The data stream is ESSENTIAL.

 

[Gary Cookc]

You won't gain much with the updated injectors, if the injectors aren't the problem.

When was the last time the O2 sensors were changed? How old are the spark plugs, plug wires, cap and rotor? How old are the air and fuel filters? Is the charcoal canister saturated? Does the PCV system work right? What is your fuel pressure under load? Does the fuel pressure hold when you shut the truck off?

"Stinking" can mean that your catalyst has been poisoned. Maybe it recovers when you fix what's wrong...maybe you replace the catalyst(s).

Connect a scan tool, look at the sensor data, and then look at the output data. Look at the cylinder-by-cylinder misfire counts, and misfire history.

"Codes" can be helpful. The data stream is ESSENTIAL.

New tuneup, O2 sensors, pcv, and catalytic converters are fairlr new. Have not looked at the charcoal cannister. Maybe I will wait a while and do a little more checking. Thanks for the info. Wasn't sure about the cheaper mpfi units. Thanks again for the help.

 

[TXStepside]

i went with the upgraded ac delco unit when i replaced the intake gasket on a 97 350 vortec. throttle was much more responsive with the upgrade