5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well the TPS did not fix it. My MAP sensor, TPS and injectors were all purchased at local auto parts store and were cross referenced to fit VP but I believe they are all just aftermarket GM replacement parts. Would this matter or make a difference? I will check the injector pulse as soon as I get a chance. If the injectors are failing when the MAP vacuum is hooked up what will that tell me? I will probably be putting it in the shop next week.

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

He has an MEFI3!

If he's fine at WOT, then the injectors are fine!
It's during throttle up that he has an issue, something is telling the ECU the wrong information at that time, causing the ECU to either deliver the wrong timing advance, or fuel delivery.

 

[gbeltran]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

When you say you converted it to a 5.7 did you use an ECU from the 5.7 or just replace the long block? I think they are different from the 5.0 to the 5.7 as far as fuel mapping and such. May be part of what's causing your issue, maybe it's too lean in the midrange.

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well the TPS did not fix it. My MAP sensor, TPS and injectors were all purchased at local auto parts store and were cross referenced to fit VP but I believe they are all just aftermarket GM replacement parts. Would this matter or make a difference? I will check the injector pulse as soon as I get a chance. If the injectors are failing when the MAP vacuum is hooked up what will that tell me? I will probably be putting it in the shop next week.

Hmm did they The parts store oder your injectors by part number or by a 5.7 injector guide. A PEFS has 454 injectors..There should be two orange bands on top of the injector input pins

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

He has an MEFI3!

If he's fine at WOT, then the injectors are fine!
It's during throttle up that he has an issue, something is telling the ECU the wrong information at that time, causing the ECU to either deliver the wrong timing advance, or fuel delivery.

Same thing just a few more tables and OS capability..On the 4b that is.

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

When you say you converted it to a 5.7 did you use an ECU from the 5.7 or just replace the long block? I think they are different from the 5.0 to the 5.7 as far as fuel mapping and such. May be part of what's causing your issue, maybe it's too lean in the midrange.

Very real possibility there..you would need the ecu remapped going from a 5.0 to 5.7

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

When you say you converted it to a 5.7 did you use an ECU from the 5.7 or just replace the long block? I think they are different from the 5.0 to the 5.7 as far as fuel mapping and such. May be part of what's causing your issue, maybe it's too lean in the midrange.

I am not sure if the ECU was replaced or remapped (not to my knowledge). I do know that it ran great when I got it out of the shop last year, as well as the first few outings this year. The repair shop that originally did the work is no longer around. As far as the injectors, the parts store cross referenced the part number so I would assume they would be the 454 injectors. I will check though to be sure. Thanks again everyone for all the tips and great info!

 

[BreakOutAnotherThousand]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Hmm did they The parts store oder your injectors by part number or by a 5.7 injector guide. A PEFS has 454 injectors..There should be two orange bands on top of the injector input pins

I'm now leaning on your side. I didnt know the OP bought injectors at the parts house!!

 

[jkel1124]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

I'm now leaning on your side. I didnt know the OP bought injectors at the parts house!!

Yes I buy parts from the parts house. Just give them the VP part numbers and they can usually just cross reference (they're the same parts). Anyhow I finally traced down the problem and fixed it. This is going to sound dumb but one of the spark plugs was cracked. Not sure how it happened but I #3 was cracked and apparently not firing. Changed out all the plugs and it runs as good as ever. Thanks again to everyone who responded and helped out!

 

[Tail_Gunner]

Re: 5.0 / 5.7 GI PEFS cutting out and popping at mid-range rpm

Well its spark or fuel..One of the great things about tbi..you can watch your injectors deliver fuel...(fun stuff)..

Just put the muff's on run it up to 3000 and watch your injectors if your getting uneven fuel they will show the same pattern your engine is missing at...Thats a old motor have you changed your cap it may be porous or cracked..wires..And again you may need to take contact cleaner and clean all of your FI contacts.

And of course you can take a plug wire put your finger in the plug hole turn it over and see if it hurts...:facepalm:..

Good thing you didnt have to stick your finger in the plug wire....

Glad it was so easy a fix