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Based upon my research, the CSFI systems used in GM's Vortec engines during the mid to later 90's are problematic. As such, it does not appear uncommon to convert these to MPFI system.

I have a 96 Chevy Express/G10 van with a 5.0 CSFI. Currently, the van idles rough, sometimes has a strong exhaust odor, makes a "pinging" noise occasionally (mostly around 30 - 40mph, light acceleration or deceleration), surges/misses primarily during deceleration when cold, and occasionally hesitates under heavy load. My initial impression was a vacuum leak (seems like it is running lean). I have spent significant time and money in attempting to diagnose this issue. The "Check Engine" light is not on. I have cleaned the throttle body, EGR valve, replaced plugs, wires, distributor cap and rotor, and changed the fuel and air filters. I have recently had an leak at the right exhaust flange, and no one seems to be able to find a vacuum leak. The readings on my vacuum gauge looked good. While I have not tested it personally, a shop tested the fuel pressure levels and said they were acceptable.

As such, I am starting to wonder if the injection system could be the culprit. To clarify, I am curious is the symptoms outlined above could be caused by problems with the poppets and, is it possible that such a problem would not throw a misfire (or other) code? Is there any accurate way to determine whether or not the CSFI system is in need of replacement? It is quite an expensive endeavor, not something I want to try on a whim.

Thanks.

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    If you're hearing the same noise from acceleration or deceleration, what you're hearing is not pinging. Pinging should not be happening upon deceleration. Pinging only happens under load, which can only occur during acceleration. If the shop tested the fuel pressure, did they check it while the van is in use? Also, what was the "acceptable" amount of fuel pressure they suggested? I'm leaning towards a fueling issue.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 25 '18 at 14:39
  • Thanks @Pᴀᴜʟsᴛᴇʀ2. What I described a s"pinging" also occurs at idle occasionally, so I suspect it may not be the right description in the technical sense (not sure how else to describe it though). It is a brief, "tinny" sound. To my understanding they checked the fuel pressure at various operating temps, but, as I was not the one who actually spoke to them, I cannot be certain. Sounds like I might be best off checking it myself before doing anything drastic.
    – KellyM
    Mar 25 '18 at 14:54
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    If you check the fuel pressure, you need to check it under different engine speeds and loads, not necessarily different operating temperatures. It could be getting fuel starved under load. Realistically it's just one thing which needs to be eliminated as an issue.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 25 '18 at 15:17
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    I have read that even Chevy mechanics recommend getting rid of those poppets. Save up the $400 and put in an aftermarket kit, even if that doesn't turn out to be your issue.
    – Jimmy Fix-it
    Mar 25 '18 at 16:37
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    Just checked, as cheap as $213 for conversion kit from popular on-line supplier.
    – Jimmy Fix-it
    Mar 25 '18 at 16:45

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