Question about 1999 Chevrolet Silverado 1500

1 Answer

Has a 6.0 L with bad misfire under a load and is

99 chevy silverado 2500 4x4
Has a 6.0 L with bad misfire under a load and is not setting a code.
San tool is showing up to 175 misfires per cycle. sometimes it would show number 1 misfire in the data part of the scan tool, still not setting a code even after more than 2 different cold to warm trips. I swapped the #1 coil, plug and wire with the #3 coil, plug and wire. It still showed #1 as misfiring
sometimes but mostly would show the total misfires. I cleaned the mas air flow sensor, and no change. I did a injector balance test and all injectors tested the same. I checked for a vacuum leak with smoke checker machine, no leaks. I don't understand why it won't set a misfire code. Help thanks, Brad

Posted by on


1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.


    An expert whose answer got voted for 500 times.

  • Master
  • 1,985 Answers

Hi Brad,
I ran into the same problem your going thru,
swapped cylinder plug and wire ,and the scan kep telling me it was still seeing the problem on the same cylinder,
smoked it too,nothing made sense!
Until i took the whole fuel rail off carefully not to let the fuel run out all over the engine,Had a white rag folded up and handy,tilted the rail assembly and left the fuel run on the cloth,OMG! the rust that came out of there,
I pulled every injector out of the rail,cleaned the inside of the rail with air pressure and carb cleaner.
Its when I was checking the injectors that I found the culprit,the rust pieces had made it thru the injector but were trapped in the screen of the injector!
I hope this cures your.

Posted on Dec 11, 2009


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

01 chevy Silverado 2500 misfires multiple cylinders replace 02 sensor map sensor fuel injector cleaned maf sensor it is throwing a code for knock senor 2 circuit my question is can a knock senor be bad...

No a knock sensor can not make a misfire. Check the coils, plugs and fuel pressure .The random misfires are cause the knock sensor to throw the code.

Jul 02, 2014 | Cars & Trucks

1 Answer

Innova scan tool 3160 manual

Don't need codes to have any number of problems

No misfire will ever be the same on your ford

Some coils set PO300 Codes,some show up on
a scan tool in Mode $06 under cyl misfires & some
coils you just have to walk a new one.

On a 2006 ALL the coils are bad by now, as well as the
front O2 Sensors

Change the Plugs every 3 years or every 2 on a 3 valve 5.4
or they will get stuck in there

Use the champion ones #7989

Feb 28, 2014 | Cars & Trucks

1 Answer

I have a 1999 Chevy Silverado Z71 it has over 100,000 miles. It runs great except sometimes when it gets between 50-60 MPH it will hiccup on an incline. I had the transmission flushed by the mechanic....

This sounds more like a misfire under load than a transmission issue. This is one of the most misdiagnosed problems we see on a regular basis. The fact that it is only noticeable while going up an incline leads me to believe you likely have worn out spark plugs, and/or a weak ignition coil.
While you do not have a check engine light on, this can happen when you have only a minor or very intermittent misfire. Once the misfire becomes worse or happens more often, the computer will turn on the light- or cause the light to flash indicating a serious misfire which could cause catalytic converter damage.
Try having your garage monitor their scan tool data for real time misfires while driving it under a load such as the incline you mentioned, or even while brake-torquing the engine (pushing the throttle slightly while the transmission is in gear and the wheels are chocked and brakes applies) This can help duplicate the conditions where you noticed the issue. Monitoring the misfire data can help them pinpoint which cylinder(s) is misfiring and swapping spark plugs or ignition coils between cylinders can determine which component is causing the issue.

Oct 12, 2017 | 1999 Chevrolet Silverado 1500

1 Answer

02 chevy 2500hd 6.0 ses light flashing at40mph an gose out at 75mph

The SES light flashing means the engine management software has detected a misfire condition resulting in exceeding 3 times the federal limit of emissions. Under heavy load such as acceleration one or more cylinders are misfiring and once cruising speed is reached the engine is under a lighter load (10 to 20 percent ) that is why it stops flashing several causes of misfires are worn spark plugs ,spark plug wires, faulty ignition coil or coils fuel injector or fuel pressure problems a quick check of the computer to retrieve trouble codes should identify the problem cylinder or cylinders and will direct you in the right direction to find the faulty component but will not tell you exactly what is wrong certain test must be performed to isolate the cause.

Dec 05, 2012 | 2004 Chevrolet Silverado 1500 Crew Cab

1 Answer

After putting gas in my car, why did it start shaking really bad and idling real high?

After a fill up, the fumes in the gas tank are very concentrated. If problem with evap system, it could cause problems after a fill-up. Just a thought.

Mar 10, 2017 | Cars & Trucks

1 Answer

I have a mystery truck! Bank one misfires under a load. Removed cats, new plugs and wires, fuel pressure at rail is great. Whats the f@%#$n problem? I got no trouble codes! its a mystery! 2005 chevy...

you could have a bad injector at that cylinder or a bad coil that runs that cylinder. If I remember there is 1 coil for each cylinder. How do you know which bank is miss firing without a code set?

May 31, 2010 | Chevrolet 1500 Cars & Trucks

1 Answer

99 chevy silverado 4x4 getting code p0304 coad changed plugs wires and coil still getting code, runs rough and cranks for a long time before it starts

You could have a faulty Fuel injector problem with your poppet valve. There common to go bad and start to leak causing misfires and ruff idle. There is an upgrade to the CSFI to covert to MFI system.

Here is a link that should help you with your P0304:

Good luck and thank you for using fixya

Mar 08, 2010 | 1999 Chevrolet Silverado 1500

1 Answer

99 vitara misfire?

check for codes, p0300 is multiple cylinder misfire, p0301-p0304 is for cylinder 1 through 4, could be bad plug or coil, try switching and see if problem moves to different cylinder

Nov 16, 2008 | 1999 Suzuki Vitara

1 Answer

99 chevy silverado service engine soon light is flashing when driving

you have to read out the codes. po300 is misfire detected. maybe a coil or injector. could also be intake leak

Nov 06, 2008 | 2002 Chevrolet Silverado 1500

Not finding what you are looking for?
1999 Chevrolet Silverado 1500 Logo

849 people viewed this question

Ask a Question

Usually answered in minutes!

Top Chevrolet Experts


Level 3 Expert

83096 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22382 Answers

Ronny Bennett Sr.
Ronny Bennett Sr.

Level 3 Expert

6927 Answers

Are you a Chevrolet Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides