injection issues? cutout

[Dillon79scotts]

So i have a 2000 chevy 5.3l, swapped into my 79 chevy 4x4.

runs about 50-60 psi depending on the vacuum of the engine.

I just recently started having a missfire, not bad enough to throw the check engine light on.

I was thinking it may be because i have a exhaust leak before the o2 sensor for some time now and it may have fouled a plug.
NOT THE CASE. i pulled both sides out and they all looked new still ( only month old AC delco's)
ONE DTC CODE I AM GETTING IS IDLE AIR CIRCUIT HIGHER THAN SET VALUE (or something along those lines)

I swapped coils with known good set.
i also just did injectors from another intake (same part number of injector)
and still no change.
tested them all with a noid light. every injector plug-in lights it up.

but are they firing on time?
could this even be a injector ground wire issue?

cam position sensor?
crank position sensor?
knock sensor? ( these are just my assumptions..)

if i can get some help with this and get my LS back on the road i would be very happy.

appreciate any help.
thanks

[Shon]

noid lites are good to tell you they are being told to fire but you do not know if anything is being squirted from those injectors. Take the rails, with injectors still attached, get a large bucket and crank over truck, have someone crank while another watches all 8 injectors fire, they will squirt, if they are not then it will need to be replaced. I had 4 that were not squirting, truck would run but it just was not right, did this, found them, replaced and been going strong since.
You should also clear the IAC code and see if it comes back, if it comes back I would clean and/or replace the IAC.
Its always good to double check all the grounds.
If the other sensors are bad you should be getting those codes.

[Dillon79scotts]

Originally Posted by Shon

noid lites are good to tell you they are being told to fire but you do not know if anything is being squirted from those injectors. Take the rails, with injectors still attached, get a large bucket and crank over truck, have someone crank while another watches all 8 injectors fire, they will squirt, if they are not then it will need to be replaced. I had 4 that were not squirting, truck would run but it just was not right, did this, found them, replaced and been going strong since.
You should also clear the IAC code and see if it comes back, if it comes back I would clean and/or replace the IAC.
Its always good to double check all the grounds.
If the other sensors are bad you should be getting those codes.

thanks shon,

yeah thats what i was also thinking. i had my set that was originally in the intake, and it was doing this. so i got a wrecking yard set (they were clean) and exact same part number. my problem is still the same..

all the injectors have o rings, and from day before i tested fuel pressure, was about 55 to 60.

[Shon]

What does "they were clean" mean? ie they cleaned them with some soap and water or they ran cleaner thru them and they worked??
I would put in rail and make sure they are firing....I got a whole set of 'clean' injectors...but they dont fire....
And if you were missing an O-ring, you would know it, fuel would spray out in a hurry!!!!

[Dillon79scotts]

There we're from a intake on a engine. Were cleaner all together than mine. But I understand what your saying
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[Dillon79scotts]

Still haven't found a set issue with it. Was thinking it was my harness but I inspected it everywhere. My computer isn't picking up any misfire but its obvious that there is a miss.

Ido what else to try besides a ecmor maybe a.burnt valve
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[OKGMC4]

These are notorious for a bad fuel regulator causing a miss. If yours is on the rail (should be in 2000) on the drivers side... start the engine and pull the vacuum hose off the regulator. If the fuel regulator spits fuel out the vacuum port, it is bad. About $50 part if I remember right.

[Dillon79scotts]

Originally Posted by OKGMC4

These are notorious for a bad fuel regulator causing a miss. If yours is on the rail (should be in 2000) on the drivers side... start the engine and pull the vacuum hose off the regulator. If the fuel regulator spits fuel out the vacuum port, it is bad. About $50 part if I remember right.

thanks, but yeah i know that trick. not a bad regulator.

SO today i hooked up efi live, and found that cylinder 5 was missing the most..
check volts to the coil, and volts to the injector.. both had 14.. swapped plug wires and plugs.. and no difference...


any ideas? could this be a crank or cam sensor?

[BR3W CITY]

you can try the sensor re-learn and see if it makes a difference

[OKGMC4]

But there is a code for the sensor relearn (CASE learn) and I've read on three different sites that that code won't affect how the truck runs, all it does is monitor misfires. Mine is throwing it right now and runs fine, until I can get it to a better scan tool. Sounds like maybe a compression check is in order to see if there might be a mechanical problem with #5?

[BR3W CITY]

^you may be right, I've never needed it, I thought it was so you could prove-out the sensor against a "real" failure

Dillon
you also say "missing the most", how many other cylinder missfires does it report? Single instance misfire would throw a code and store it, multiple instance/multiple misfire should flash the dtc light iirc.

Compression check might not be a bad idea.


Is it possible for the IAT thats built into the truck MAF to fail seperately? That would be a unique one.

[Dillon79scotts]

Originally Posted by BR3W CITY

^you may be right, I've never needed it, I thought it was so you could prove-out the sensor against a "real" failure

Dillon
you also say "missing the most", how many other cylinder missfires does it report? Single instance misfire would throw a code and store it, multiple instance/multiple misfire should flash the dtc light iirc.

Compression check might not be a bad idea.


Is it possible for the IAT thats built into the truck MAF to fail seperately? That would be a unique one.

its showing cylinder 5 missfire, and it does flash the dtc most of the time

[Dillon79scotts]

ill be doing a compression check this monday i hope. i dont think thats the issue tho

[Dillon79scotts]

Originally Posted by Dillon79scotts

ill be doing a compression check this monday i hope. i dont think thats the issue tho

i did a compression check... and sure enough that wasnt the problem. i was almost certain it wasnt, but ya never know.

150psi is what i got.

[OldCreek]

How does that plug look on #5?

How are your fuel trims? (HPtuners or efi live, etc)

Do yourself a favor and pull #5 injector and clean it again! Don't just soak it in gas/cleaner. Attach a small hose to the intake side and fill it with cleaner and then run the injector with a 9 volt battery... Does it spray? How is the spray pattern. You can have a stuck/dirty injector even with it being in normal resistance range. Does the injector make a clicking sound when you attach the battery? That is the injector opening and closing. You could put a stethoscope on it before you pull it.

Then, clean all the others.

Any other codes? List them all.

I would assume the idle air valve could fail but wouldn't that cause the engine to misfire on more than one cylinder? Fuel trims would be helpful....

[Dillon79scotts]

Originally Posted by OldCreek

How does that plug look on #5?

How are your fuel trims? (HPtuners or efi live, etc)

Do yourself a favor and pull #5 injector and clean it again! Don't just soak it in gas/cleaner. Attach a small hose to the intake side and fill it with cleaner and then run the injector with a 9 volt battery... Does it spray? How is the spray pattern. You can have a stuck/dirty injector even with it being in normal resistance range. Does the injector make a clicking sound when you attach the battery? That is the injector opening and closing. You could put a stethoscope on it before you pull it.

Then, clean all the others.

Any other codes? List them all.

I would assume the idle air valve could fail but wouldn't that cause the engine to misfire on more than one cylinder? Fuel trims would be helpful....

I'll check fuel trims, and let you know. It's got a different injector that was good, well I'll swap a injector from another bank.

I know that one bank was at like 13% and one
as staying around 1%. The 02 short trims
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[Dillon79scotts]

Plug looks just like any other. it acts as tho there is no spray.
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[Dillon79scotts]

Originally Posted by Dillon79scotts

Plug looks just like any other. it acts as tho there is no spray.
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hopefully this helps at all?

[OldCreek]

High long term fuel trim (bank 1) and on the same side as your misfire (#5)....

I had the same thing and it was a bad injector. I did plenty of online research and, basically, came up with this list (from another thread):

-Pull your plugs and see if any are wet or anything else.

-Stick a stethoscope on ALL of your injectors and listen if they all make a similar ticking sound of similar decibel. A stuck injector will cause you to run rich. You will see high fuel trims if so.

-Take your ohmmeter and check that all injectors are within specs (a stuck injector can still have normal resistance...ask me how I know.)

-Also, you can get a "noid light" kit from autozone on loan and plug it into each injector wiring harness plug to see if each is firing correctly.

-Checking vacuum was a good idea...you could also spray some starter fluid or carb cleaner around the intake and see if your idle jumps.


I assume you, at the minimum, have an OBDII scanner... I had hptuners to help me diagnose my problem (i.e. reading fuel trim)

More obscure problems can be caused by a bad fuel pressure regulator and even holes in your vacuum lines.

If your engine has been sitting awhile I would guess issues with a stuck injector. I pulled all of mine and flushed them all...I couldn't unstick one and ended up buying a new one. It fixed all my rich/fuel trim problems.
__________________

But the basic theory is the computer is adding more fuel to that side to make up for a lean condition. What is giving you a lean condition? Vacuum leak, bad injector, no detonation from a bad plug/coil/wire, etc...

I'd focus on cylinder #5 as it is the one misfiring, albeit intermittently.


Full disclosure: I am NO mechanic. I'm just a weekend warrior trying to learn all this myself and not wanting to pay someone to fix something I might be able to...

[Shon]

so much easier to just pull the injectors out of intake and watch to make sure they are all squirting....

[Dillon79scotts]

Originally Posted by Shon

so much easier to just pull the injectors out of intake and watch to make sure they are all squirting....

come to find out injector 5 was bad after all again... even tho i swapped with another set... weird. but thanks for the help everyone.

i checked the injector to see if i heard the click. nothing

[rcrahn]

Good thread and glad to hear that you isolated it.
Injectors on my LQ9 have not been used for years during the project build. Before I fire off this engine I'm definitively having them cleaned and checked.
Worth every penny in my book
http://doctorinjector.net/index.htm

[Dillon79scotts]

Originally Posted by rcrahn

Good thread and glad to hear that you isolated it.
Injectors on my LQ9 have not been used for years during the project build. Before I fire off this engine I'm definitively having them cleaned and checked.
Worth every penny in my book
http://doctorinjector.net/index.htm

yeah, good info here.

im happy to be driving it again. although ill be selling it getting something smaller (s10) and solid axle it

[BR3W CITY]

lame, sell a classic truck with a new engine for a newer truck with solid axle? backwards homie

[Dillon79scotts]

Originally Posted by BR3W CITY

lame, sell a classic truck with a new engine for a newer truck with solid axle? backwards homie

its to wide for the trails i want, and to long.

i cant fit in alot of places.