C E L Flashing

Discussion in 'GM Powertrain' started by jssneptune, Jan 7, 2009.

  1. jssneptune

    jssneptune New Member

    1996 5.7L TBI c3500
    CEL would flash a lean condition on bank one once a week but otherwise ran great. then 2 min from home when cold out cel started flashing so I stopped and checked some things and drove it home with engine running rough. while working on it it ran again with no codes on short trips 5 miles then showing cyn 1 misfire codes. most parts have only 10,000 or less miles checked filter. fine , changed cap rotor wires checked on ohm meter spark plugs looked pretty good fuel pump sounds good truck still running rough.
    ive been tryin everything and its been broken for weeks
    any ideas
  2. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    Just to make sure we're understanding -- you're getting a P0301 code, correct? If you clear the code, do you consistently get the same code, or different codes?

    Diagnosing a misfire code basically means checking all the things that could cause a misfire. It appears that you've been through some of the ignition system, that's good. Have you checked for spark leak (lift the hood in the dark and look for sparks jumping. It often helps to use a squirt bottle to mist under the hood).

    Have you actually verified spark to cyl #1 (I like to use an inductive timing light as an initial check).

    You say the fuel pump sounds good, but that by itself doesn't diagnose the fuel system. What is your fuel pressure? In addition, this vintage CSFI system has had issues with the injectors/poppet valves -- there's a good chance that could be the problem.
  3. jssneptune

    jssneptune New Member

    yes im getting that code(301) and as soon as I clear it.It comes back within 2 minutes same code. I checked for spark on number 1 by sticking an old plug in number one wire and grounding it. I will check for spark leak tonight and am looking for a fuel pressure gauge ive only heard good things about the injectors can you elaborate Im thinking injectors but shoudn,t I have differant codes poppin. I also have bosch O2 sensors and it seems they have bad reputation.
    wish me luck its hard workin in this cold at night
  4. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    I haven't met many people on line who have "nothing but good things" to say about the poppet valves on these. GM even redesigned the CSFI to use Multec II injectors for the replacement fuel meter body, they were having so much trouble with the original poppet valves.

    I don't know that I would expect a different set of codes. My OBD2 code list indicates there are P020x codes that would point to injector wiring problems, but I'm not certain the problem with the poppet valves is that kind of electrical fault, if GM even programmed the PCM on these to trigger those codes. I know that a lot of people when they've reported problems with the injectors, it has often been accompanied by one of the misfire codes. I wish I had specific diagnostic information for determining when the injectors are at fault, but I don't. If you can't find any other explanation for a misfire on cylinder #1, I'd look carefully at those injectors.

    Have you tried a compression test to make sure it isn't mechanical fault in the engine?
  5. JMoney02

    JMoney02 Epic Member 5+ Years 500 Posts

    MRShorty's right, the poppets are crap, thats the reason for the design change so they would not have to do a recall. Also, did you change the O2 sensor? To the Bosch? If so, was it a plug/play sensor? Or did you have to cut/splice the wires? If so did you follow the directions for splicing, these universal O2 sensors are teadious creatures and wiring them incorrectly also can cause this on Bank 1 and 2...

  6. jtarms45

    jtarms45 New Member

    I had a '96 GMC 454, with the same dreaded CEL flashing and 0301 code. What mods do you have on that engine? I had an aftermarket MASS sensor, swithched back to stock. A buddy of mine had a simialr problem, stock mass sensor, we ran a compression check, he had burt intake valves from running too lean...
  7. jssneptune

    jssneptune New Member

    still workin on codes

    thanks for the replys,
    the lean condition is whats buggin me. if im having misfires from injectors shouldnt I be running rich.
    the injector harness is 450 dollars for the whole thing or 70 per injector bye some company ive never heard of whats the usual fix if its the injector on number one. the book says there calibrated so label them when taking out. what injectors are the best clymers doesnt even really say what to do in case of injector failure. Im going to find away to run some pure injector cleaner thur the lines and see if it even clears up for a moment .

    my truck is stock except for chip k & n flow masters
    compression is good and idels good at times then rough.

    who at chevy thought of puttin injectors under the intake manafold.

    O2 sensors were direct plug in but Ive heard i should have used org equipment

    any more ideas would be appreciated
  8. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    Depends on how you are measuring it. Remember that an O2 sensor detects the unburnt O2 in the exhaust. In the case of a misfire, all the O2 that went into that cylinder is coming out, so the O2 sensor could see excess O2 and report a lean condition. O2 sensor can't see unburnt fuel.

    The "preferred" fix that I've seen mentioned is to replace the entire fuel meter body with the updated design that uses Multec 2 injectors rather than poppet valves. Individual poppet valves can still be purchased, if money is more important than reliability (such as you are planning to sell the truck once you get it fixed).
  9. jssneptune

    jssneptune New Member

    what too get

    If I upgrade, what do I need too changetoo the multex two injectors. and what is the proceedures for this upgrade and maybe an idea as cost thanks
  10. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    The upgrade replaces the fuel meter body, fuel pressure regulator, and the poppet valves. My understanding has been that it comes as a complete kit with all of the above parts, and is a plug and play replacement.

    Procedure can be had in most manuals - even the DIY manuals (Chiltons/Haynes). If you don't have/like print versions, autozone.com has free electronic versions of Chiltons you can access. Look in the fuel systems sections - CSFI - fuel meter body. Basic procedure is to remove the upper intake manifold, remove the fuel meter body, then install the new one.

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