Has anyone ran into a 5.7 Chevy vortec motor that shows a misfire On a cylinder when its not actually misfiring?

100

Asked by Aug 23, 2015 at 10:26 PM about the 2002 Chevrolet Express Cargo 3 Dr G3500 Cargo Van

Question type: Maintenance & Repair

12 Answers

7,085

No, I haven't. You probably do have a misfire, just that is very subtle. The engine computer determines a misfire by the crankshaft slowing down. This is determined by the crankshaft sensor signal. This model year 5.7L was notorious for fuel injector problems. So many problems, as a matter of fact, that GM redesigned the fuel injectors. The fuel injectors are available in a complete kit of 8 injectors, and center pod w/pressure regulator. A new mounting bracket is required for correct installation, and is sold separately. The old injectors had a poppet nozzles. These were eliminated, and a replaced by miniature electric injector, at the ends of the distribution tubes. You can try a bottle of injector cleaner in your tank, such as Techron by Chevron, from your local parts store. It's the same stuff that GM sells at their dealers, and puts a GM label on it. Also, make sure your plugs, wires, cap and rotor, are good. If you have a lot of miles on them, might be time for a tune-up?

1 out of 1 people think this is helpful.
100

Thanks goodwrench good pointers but this one is a little deeper than that, The engine is a rebuild 0 mile motor ,The motor does not misfire but Snap on scanner picks up a misfire on #2 cylinder , good cap and rotor, try different distribotors, wires plugs, crank sensor and connectors , wires From crank sensor to ecm are ok .03 ohms , Spider is new , have good pulse to All 8 injectors and Also good equal Patterns On scope On All The injector circuits and crank and cam signals are good on frequency test, valves are adjusted correctly, cranking compresiĆ³n ok,running compresiĆ³n ok , leak down ok !!. Only misfire counts under a slight load not heavy and not in gear.!

1 out of 1 people think this is helpful.
61,305

It does happen. Not that often though. It's usually a PCM problem. I'd suspect that this is the case since you have a fresh rebuild and all the new accessories to go with it. I'd have the PCM flashed (programmed) using the latest software. HTH. -Jim

100

thanks Jim ,i reflash computer no change , dont think is got a Balance issue either runs so smooth,

1 out of 1 people think this is helpful.
7,085

That's a new one on me. If it's not the PCM, then you must have an issue with #2 not firing evenly, while under slight load. If someone were to tell me that they get a misfire code, while under slight load, I'd be looking for an ignition problem. But you state all is new. Is your scanner capable of viewing live misfire data? I worked for GM, and with the Tech2 scanner, this could be viewed. You could watch exactly when the misfire counts happened/incremented, and the total number of misfires. Other ideas, shot in the dark?:....slight vacuum leak near #2? Um,...since the engine is a rebuild, crank not balanced correctly? You got got me stumped.

1 out of 1 people think this is helpful.
61,305

You're welcome. Glad to try and help. -Jim

100

Driving me nuts too! Ignition shows good on scope no interruptions at all so does fuel delivery, triple check for vaccum leaks and verify EGR wasent leaking sinse is Right in front by #2. Yes i have The latest gm scanner MDI also have tech2 but hardly use it anymore. I hate to trow Parts at cars with out accurate diag but looks like i might be trowing a ECM at this one and playing , Will post The results

100

Meant to say praying not playing lol sorry guy

7,085

Thanks, please post results. I'm interested in knowing what you find. Sorry I couldn't be of much help.

100

Thank you goodwrench any pointers at this time helps , i had 2 Pretty respected techs here in Houston tx look at it and left scraching their heads .i Will for sure post results thanks.!

7,085

Just one more idea, ..... check the the routing of the injector lines on the spider. Any chance you might have 2 of them mixed up? This would not show as a dead miss, since they spray fuel before the intake valve.

100

Done that,you can actually go into injector disable mode and kill individual injectors and watch your misfire live data at same time, i have kill each individual injector and check data at each cylinder make sure The misfire was at place were injector was killed.! Example: if 2 And 8 were swap then when i kill 2 8 would misfire on data.!

Your Answer

Add photo

Related Questions

  • Misfire code 3 answers

    What could keep a brand new spark plug from firing if wires are good spark plug is new and coil is new. 1999 Chevy silverado

    1999 Chevrolet Silverado 1500 3 Dr LS Extended Cab Stepside SB

    -

    Maintenance & Repair

  • Misfire 6 answers

    I have a problem. My 2004 Chevy Silverado will idle fine for about 30 seconds then all the sudden my 6th cylinder only will start to misfire. I have changed my Mass Air Flow sensor, switched out t...

    2004 Chevrolet Silverado 1500 Z71 Ext Cab Short Bed 4WD

    -

    Maintenance & Repair

  • 97 chevy 5.7 cam crank relearn 45 answers

    When replacing the distributor on the 5.7 Chevy Vortec enginen, the instruction that came with the Distributor said that a code P1345 would be set, and that a Cam Crank relearn must be performed. Us...

    1997 Chevrolet C/K 1500 Silverado Standard Cab LB

    -

    Maintenance & Repair

  • what is causing my cylinder one misfire? 12 answers

    I own a 2006 chevy cobalt it has around 130k and never had any issues, only routine oil changes. I had a ignition switch recall called on my car, a day after hearing of the recall, i was driving on th...

    2006 Chevrolet Cobalt

    -

    Maintenance & Repair

  • Misfire 2 answers

    I have a 1999 s10 4.3l vortec, it misses in cylinder 4, I have replaced the spark plug, and plug wire, but it continues to misfire, I am thinking I have a problem with the distributor cap or the w...

    1999 Chevrolet S-10 3 Dr LS Wide Stance 4WD Extended Cab SB

    -

    Maintenance & Repair

Express Cargo

Looking for a Used Express Cargo in your area?

CarGurus has 14,138 nationwide Express Cargo listings starting at $2,990.

ZIP:

Search Chevrolet Express Cargo Questions

Chevrolet Express Cargo Experts

#1 Tom Demyan
Tom Demyan
Reputation 150
#2 Rowefast
Rowefast
Reputation 130
#3 DONCHAUMPSR
DONCHAUMPSR
Reputation 120
View All

Related Models For Sale

Used Chevrolet Express
120 Great Deals out of 5,971 listings starting at $2,499
Used Ford E-Series Cargo
95 Great Deals out of 3,173 listings starting at $1,995
Used GMC Savana Cargo
20 Great Deals out of 4,728 listings starting at $2,795
Used Chevrolet Silverado 2500HD
326 Great Deals out of 25,711 listings starting at $2,500
Used Chevrolet Astro Cargo Van
146 listings starting at $2,995
Used Ford Transit Cargo
38 Great Deals out of 17,478 listings starting at $14,500
Used GMC Savana
13 Great Deals out of 1,501 listings starting at $2,995
Used Chevrolet Silverado 1500
2,284 Great Deals out of 155,168 listings starting at $1,395
Used Dodge Sprinter Cargo
269 listings starting at $6,000
Used Ford E-Series Wagon
47 Great Deals out of 1,782 listings starting at $1,500
Used Ford E-350
234 listings starting at $495

Used Cars For Sale

2017 Chevrolet Express Cargo For Sale
9,868 listings starting at $21,382
2016 Chevrolet Express Cargo For Sale
4 Great Deals out of 1,393 listings starting at $16,995
2015 Chevrolet Express Cargo For Sale
3 Great Deals out of 184 listings starting at $16,995
2014 Chevrolet Express Cargo For Sale
3 Great Deals out of 224 listings starting at $10,950
2013 Chevrolet Express Cargo For Sale
11 Great Deals out of 262 listings starting at $7,998