2000 Tahoe misfire/backfire problem

Thats a vague description so heres a better one. Its a 2000 tahoe 5.3L with K&N cold air intake and Hypertech II programming thats both been done for about 4 years. The truck starting dying on cold startups about 2 months ago then progressed to dying hot or cold, meaning it wouldnt idle immediatly. You would have to hold the gas a little until it felt like idling on its own. My fuel consumption increased quite a bit and i kept having a rich fuel smell. I figured it was just time for a tune up so i put some new plugs and wires on with no success. Its still dying and today was much worse than its been being. It didnt want to idle today at startup for nothing in the world. If you gave it a little gas and held it, it would run all day.

Another new symptom actually falls back to the title. I think its a misfire but im told its a backfire. I think misfire due to the strong gas smell. Im told its a backfire and that chances are my fuel pump is going out.

Truth is i dont know what to call it which is why im here to begin with. I can tell you that it makes a faint "popping" in the exhaust when holding it anywhere from 1000rpm tp 2000 rpms

Another guy is trying to convince me the fuel pump is weak and im really struggling with that answer. Hopefully someone can come up with an alternate

Thats a vague description so heres a better one. Its a 2000 tahoe 5.3L with K&N cold air intake and Hypertech II programming thats both been done for about 4 years. The truck starting dying on cold startups about 2 months ago then progressed to dying hot or cold, meaning it wouldnt idle immediatly. You would have to hold the gas a little until it felt like idling on its own. My fuel consumption increased quite a bit and i kept having a rich fuel smell. I figured it was just time for a tune up so i put some new plugs and wires on with no success. Its still dying and today was much worse than its been being. It didnt want to idle today at startup for nothing in the world. If you gave it a little gas and held it, it would run all day.

Another new symptom actually falls back to the title. I think its a misfire but im told its a backfire. I think misfire due to the strong gas smell. Im told its a backfire and that chances are my fuel pump is going out.

Truth is i dont know what to call it which is why im here to begin with. I can tell you that it makes a faint "popping" in the exhaust when holding it anywhere from 1000rpm tp 2000 rpms

Another guy is trying to convince me the fuel pump is weak and im really struggling with that answer. Hopefully someone can come up with an alternate

Fuel pump can be checked with a good fuel pressure test.

Back firing and miss fire can be crossed plug wire or bad dist cap and rotor.

Is the engine missing on any cylinders?
Good hot blue spark to all plugs?

No distributor, 8 coils. 1 coil over each cylinder with a 6" plug wire.

Yes i think one of them are missing but dont know which one, not getting any error codes and i havent manually checked each one as of yet. At least now i have a starting point.

No distributor, 8 coils. 1 coil over each cylinder with a 6" plug wire.

Yes i think one of them are missing but dont know which one, not getting any error codes and i havent manually checked each one as of yet. At least now i have a starting point.

the plug wires should be 500-700ohms....

you may very well have a intake manifold leak..or the fuel regulator is defective ,,,,internal diaphram has a hole in it causing fuel to get sucked into the intake,,,remove the regulator vac, line and inspect for fuel...

I hav ea 2000 Tahoe 5.3 doing the same thing. It wasn't the coil packs. I replaced ALL of them and NOTHING changed. So I returned them. Getting ready to take it to the dealer.

Thats a vague description so heres a better one. Its a 2000 tahoe 5.3L with K&N cold air intake and Hypertech II programming thats both been done for about 4 years. The truck starting dying on cold startups about 2 months ago then progressed to dying hot or cold, meaning it wouldnt idle immediatly. You would have to hold the gas a little until it felt like idling on its own. My fuel consumption increased quite a bit and i kept having a rich fuel smell. I figured it was just time for a tune up so i put some new plugs and wires on with no success. Its still dying and today was much worse than its been being. It didnt want to idle today at startup for nothing in the world. If you gave it a little gas and held it, it would run all day.

Another new symptom actually falls back to the title. I think its a misfire but im told its a backfire. I think misfire due to the strong gas smell. Im told its a backfire and that chances are my fuel pump is going out.

Truth is i dont know what to call it which is why im here to begin with. I can tell you that it makes a faint "popping" in the exhaust when holding it anywhere from 1000rpm tp 2000 rpms

Another guy is trying to convince me the fuel pump is weak and im really struggling with that answer. Hopefully someone can come up with an alternate




Have you found out what is going on??? I'm having the same problem & I'm not that thrilled about going to the dealer over it.

Just a thought here, but have you checked your Mass Air Flow sensor. Since you have the Cold Air Intake oil can contaminate the sensor causing driveability concerns.

As stated just a thought.

Have you found out what is going on??? I'm having the same problem & I'm not that thrilled about going to the dealer over it.

so have you opened the hood and inspect/test anything ?

Just a thought here, but have you checked your Mass Air Flow sensor. Since you have the Cold Air Intake oil can contaminate the sensor causing driveability concerns.

As stated just a thought.


I did, sensor appeared clean and dry. Unplugged it with truck running and received error code as i should have. Plugged it back in and cleared it. Still running a little rough. Its just enough that if someone borrowed my truck they would never notice it but i been driving it 4 years, i know its off. The cranking is obvious but if reference to the miss. I havent had the chance to get anything else checked on it yet, personal issues jumped in the way as usual. You try to get one thing done and 100 other things fall apart, gotta love it.

ps, i can check plug wire ohms and vac line tomorrow myself. Will post results.

While your checking stuff give your alternator and battery a check. I know from past experiance that a weak alternator will cause a problem similar to yours. It cant hurt to put a mutimeter on your battery with the engine off and with the engine at idle. Bat should be around 12.5 mabe a little higher and while checking the alt with engine idleing it should be around 14.5 could also be a little higher or just a little bit lower but not much lower.

12.5 dead and 14.1 at idle. Wires showed to be 900 ohm average except for #1 which was over 1K for some reason. Odder than that i could unplug it and not notice a diff yet i could unplug any cyl and not see a diff. Miss was consistent all across.

Found no fuel in vac line

certainly 1k is too much resistance but is 900?

Sounds like i might have an exhaust leak right at collector flange too, tap coming from that area i think. I guess i have to crawl under there and find out :grinyes:

Havent had fuel pressure checked or had chance to change filter yet


i appreciate the responses, must explain that im slow at getting this done due to a ton of other things one including dental work :crying:. So, thanks for the help and sorry for the delays.

oh, havent pulled plugs and checked spark either but its on the list too

changed pressure regulator valve today on a whim, wasted $51 bucks.

Oh well, live and learn.

I was told to wait until nightfall and check to see if i have any spark jumping taking place. I guess thats next.

12.5 dead and 14.1 at idle. Wires showed to be 900 ohm average except for #1 which was over 1K for some reason. Odder than that i could unplug it and not notice a diff yet i could unplug any cyl and not see a diff. Miss was consistent all across.

Found no fuel in vac line

certainly 1k is too much resistance but is 900?

Sounds like i might have an exhaust leak right at collector flange too, tap coming from that area i think. I guess i have to crawl under there and find out :grinyes:

Havent had fuel pressure checked or had chance to change filter yet


i appreciate the responses, must explain that im slow at getting this done due to a ton of other things one including dental work :crying:. So, thanks for the help and sorry for the delays.

the plug wire resistance should be 500-650 ohms,,,900 plus is too high...
plugs should be replaced if 50,ooomi or at least checked for gap tip damage...

the fuel pressure must be above 53 psi ....60 psi is perfect and it holds pressure on shut down..

the exhaust manifold leak is common the bolts break..use a ratchet and tighten to 10 ft lbs to see if the head falls off...

all these items could cause your problem cost to check zero...

the plug wire resistance should be 500-650 ohms,,,900 plus is too high...
plugs should be replaced if 50,ooomi or at least checked for gap tip damage...

the fuel pressure must be above 53 psi ....60 psi is perfect and it holds pressure on shut down..

the exhaust manifold leak is common the bolts break..use a ratchet and tighten to 10 ft lbs to see if the head falls off...

all these items could cause your problem cost to check zero...

plugs and wires are brand new and plugs are platinum 4's, no gap setting. Note that mentioned exhaust leak is not where the manifold meets the head.

I used anti seize on the plug threads and i used plug wire boot grease on the wires.

plugs and wires are brand new and plugs are platinum 4's, no gap setting. Note that mentioned exhaust leak is not where the manifold meets the head.

I used anti seize on the plug threads and i used plug wire boot grease on the wires.

P-4 plugs made by bosch many have had problems with miss fire.
most all here recommend a/c delco...

new wires must be the same resistance as the spec. resistance the oem wire measures 500-650 ohms your wires are not the correct spec...who made them ?

any exhaust leak will cause problems with the PCM/computer if it is near the engine this will throw the KS out of range..

These are the wires, oreilly's local store had 2 sets and the person that was trying to sell them to me had no idea what the difference was between the two other than roughly $30. I made him get me both sets and neither set had any markings with details as to ohms, size or anything. The information was nothing more than what you will see in this link. The wires themselves dont even have the info stamped on them. I shouldnt have bought them but at the time i just didnt feel like going anywhere else. So theres my BS excuse to why i bought the crap below :iceslolan

http://www.oreillyauto.com/EW3/ProductDetail.do?id=59979883&line=OMS&itemNumber=9646&manualReplCategoryIndex=49&vehicle=2000CHEVROLETTAHOEV8-325%20%205.3L&bid=1237586439582&cycleCount=1916&currentPage=4


Now the plugs are another story all together. Needless to say they were a little more costly.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-Bosch_11430011-P_960_R|GRPTUNEAMS_489626729___ (http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-Bosch_11430011-P_960_R%7CGRPTUNEAMS_489626729___)

They were bought at a seperate time at obviously a seperate place. I was leary when i bought them and indeed asked will they work right my my tahoe with there being so much computer controled crap on it and i was told yea, they will work great.

This kinda stuff makes me with i had a 69 c-10 stepside with the old trusty 4 bolt main 350, turbo 350 tranny and a good ole holly sitting on top. Didnt matter what brand plugs were in it, what wires, nothing. Set the gap, screw them in and drive the damn thing until the wheels fall off.

These are the wires, oreilly's local store had 2 sets and the person that was trying to sell them to me had no idea what the difference was between the two other than roughly $30. I made him get me both sets and neither set had any markings with details as to ohms, size or anything. The information was nothing more than what you will see in this link. The wires themselves dont even have the info stamped on them. I shouldnt have bought them but at the time i just didnt feel like going anywhere else. So theres my BS excuse to why i bought the crap below :iceslolan

http://www.oreillyauto.com/EW3/ProductDetail.do?id=59979883&line=OMS&itemNumber=9646&manualReplCategoryIndex=49&vehicle=2000CHEVROLETTAHOEV8-325%20%205.3L&bid=1237586439582&cycleCount=1916&currentPage=4


Now the plugs are another story all together. Needless to say they were a little more costly.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-Bosch_11430011-P_960_R|GRPTUNEAMS_489626729___ (http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-Bosch_11430011-P_960_R%7CGRPTUNEAMS_489626729___)

They were bought at a seperate time at obviously a seperate place. I was leary when i bought them and indeed asked will they work right my my tahoe with there being so much computer controled crap on it and i was told yea, they will work great.

This kinda stuff makes me with i had a 69 c-10 stepside with the old trusty 4 bolt main 350, turbo 350 tranny and a good ole holly sitting on top. Didnt matter what brand plugs were in it, what wires, nothing. Set the gap, screw them in and drive the damn thing until the wheels fall off.

Pitch the Bosch plugs in the trash can and get the Ac delco plugs the good book calls for.:rofl:

I took my 00 Tahoe 5.3 to the dealer to find that Part#3330PCT regulator needed replaced. All I know is it was something w/ the fuel dumping when it wasn't needed. It only costed me $300 !!!!! At the dealer soooo. It WAS worth it.

I took my 00 Tahoe 5.3 to the dealer to find that Part#3330PCT regulator needed replaced. All I know is it was something w/ the fuel dumping when it wasn't needed. It only costed me $300 !!!!! At the dealer soooo. It WAS worth it.

It is good that you got it fixed but your dealer pulled a Jessie James hold up on you.

300$ for a 50$ part and 15 minutes labor.

Within a year or two it will probably do it again.
My brother in law has went threw 4-5 of them.
If so pull vacuum hose off of reg and gook for gas in the hose.
If so just buy a fuel pressure reg and put it on yourself in 15 minutes.
An save the other 250$ for mad money.:rofl:

It is good that you got it fixed but your dealer pulled a Jessie James hold up on you.

300$ for a 50$ part and 15 minutes labor.

Within a year or two it will probably do it again.
My brother in law has went threw 4-5 of them.
If so pull vacuum hose off of reg and gook for gas in the hose.
If so just buy a fuel pressure reg and put it on yourself in 15 minutes.
An save the other 250$ for mad money.:rofl:


Thanks for the input. Get me once shame on you- get me twice shame on me!!
Thanks again, I'll deffenitly do it myself in the future. To be honest I was happy it wasn't anything worse.

:banghead: Chris

Fuel pressure idles at 50lbs, rev engine and it jumps to 55ish. Unplug regulator and its 60lbs. Mechanic that tested seems to think thats within spec and possibly the catalytic converter is stopped up.

Fuel pressure idles at 50lbs, rev engine and it jumps to 55ish. Unplug regulator and its 60lbs. Mechanic that tested seems to think thats within spec and possibly the catalytic converter is stopped up.


Fuel pressure is not up to specs.
Proper testing before seems to think thats it is bad.
A vacuum gauge will test for pluged cat.
What is vacuum reading at idle and speed up?

On the fuel pressure.
You fuel pressure is to low.
Specs on it is 55/62 lbs of pressure
Here is some guide lines of fuel pressure checking.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 55-66 fuel pressure.
Cold start should be 55/62 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/62 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT

Might need intake gaskets,blow out and sucking in air causing a miss.4.8s,5.3s and 6.0s are known for intake gaskets blowing out which is a very common problem.It is a plastic gasket which is a joke.Spray a can of carb cleaner near the intake gasket areas and if it changes,intake gaskets are bad.

Fuel pressure idles at 50lbs, rev engine and it jumps to 55ish. Unplug regulator and its 60lbs. Mechanic that tested seems to think thats within spec and possibly the catalytic converter is stopped up.


this pressure of 50psi is not high enough ...you have fuel pump problems,,,,this is consistant with your issues..this is where to start...

53 psi is the lowest acceptible amount,,,,meaning that the fuel pump will soon fail....and the the fuel pump is not working properly..

the instuctions MT 2500 gave should be followed...