Need help trying to get truck back on the road please lmk if you have had an issue similar and how you fixed it!

[Road Trip]

One other thought - though I don't think it is your problem - Passlock. I've forgotten if it cuts fuel, spark, or both but a typical symptom is the engine fires up then immediately dies.

Greetings from the other side of the pond. According to the FSM the Passlock security feature exerts
it's no start control via telling the VCM whether or not to drive or disable the actual fuel injectors. (See attached.)

I think this is the only area disabled, for I can't find any mention of the Ignition in this section of the book.

And the theory that the Fuel Pump Relay is deactivated by the Passlock would not result in positively killing the engine
if the keys don't match. Because if the thief cranks the engine long enough, the oil pressure will get above the 4 psi
threshold of the backup switch, the fuel pump would now receive power from this redundant power path, & then the
truck would still start. (!)

We got a bunch of codes to go away but I’m having like a hard start and bad idle and if you give it any throttle it just sounds like it’s struggling so bad to rev up and then sometimes it will just die out and backfire.

You wouldn't happen to have written down a list of all the codes you cleared? This could give us important clues
as to where we should look next in order to fix whatever is left. (On big multi-faceted problems like this, you can
never have too much failure context.)

****

Let's give some thought to what has & hasn't been tried to date, and see if anything comes to mind.

Forgetting computers for a moment, back in the carburetor days I could have a bowl full of fuel, the accelerator
pump nozzles are shooting like they are supposed to, the gasoline is known good, the choke isn't stuck closed, etc.
And the dizzy is throwing good sparks towards each of the plugs in the correct sequence. Plenty of parts have
been substituted with no change in behavior.

But if unbeknownst to me some prankster had stuffed a potato up the tailpipe, you can get that barely starts,
runs for a second or two, struggling to run, and dies -- even though all the normal no-start stuff has been
checked & rechecked. (TBI analog: Engine doesn't track VE tables due to inability to breathe because of brick wall EGR.)

****

Coming full circle, if you had a bunch of 'O2 too rich' or P0300 / P030x DTCs in the history list, and the root cause(s)
of these issues have since been since cleared, then we could infer that there's a good chance that you have a
damaged/melted/plugged up cat(s) behind your engine? Q: Do you ever remember seeing a flashing SES light
while driving? This would further support the melted cat/plugged up exhaust theory.

****

But if we don't have that list of DTCs, I'm reduced to conjecture in public. Not my strong suit.

But if you and your local support team are convinced that you have good Spark + Fuel + Compression, but it
still won't run right, AND you haven't already dropped the exhaust, then that's where I'd go next. Don't know
if I'd bet a steak dinner on it, but with a partially/mostly plugged exhaust it *is* possible to experience symptoms
like you describe.

I know just how frustrating this can become. But if we approach this with an incremental Building Block approach
(ie: assume everything is BAD, and step by step prove each subsystem is good) ...eventually it will run again.

For once you have the internal combustion triad correct, it *has* to run:

xc_hide_links_from_guests_guests_error_hide_media

:0)

Especially if you still have cats, drop the exhaust & see what happens. Fingers crossed
you find the answer asap.

Best of luck. And let us know what you discover --

 

[HotWheelsBurban]

Greetings from the other side of the pond. According to the FSM the Passlock security feature exerts
it's no start control via telling the VCM whether or not to drive or disable the actual fuel injectors. (See attached.)

I think this is the only area disabled, for I can't find any mention of the Ignition in this section of the book.

And the theory that the Fuel Pump Relay is deactivated by the Passlock would not result in positively killing the engine
if the keys don't match. Because if the thief cranks the engine long enough, the oil pressure will get above the 4 psi
threshold, and the fuel pump would receive power from this redundant power path, & then the truck would still start. (!)




You wouldn't happen to have written down a list of all the codes you cleared? This could give us important clues
as to where we should look next in order to fix whatever is left. (On big multi-faceted problems like this, you can
never have too much failure context.)

****

Let's give some thought to what has & hasn't been tried to date, and see if anything comes to mind.

Forgetting computers for a moment, back in the carburetor days I could have a bowl full of fuel, the accelerator
pumps are shooting like they are supposed to, the gasoline is known good, the choke isn't stuck closed, etc.
And the dizzy is throwing good sparks towards each of the plugs in the correct sequence. Plenty of parts have
been substituted with no change in behavior.

But if unbeknownst to me some prankster had stuffed a potato up the tailpipe, you can get that barely starts,
runs for a second or two, struggling to run, and dies -- even though all the normal no-start stuff has been
checked & rechecked. (!)

****

Coming full circle, if you had a bunch of 'O2 too rich' or P0300 / P030x DTCs in the history list, and the root cause(s)
of these issues have since been since cleared, then we could infer that there's a good chance that you have a
damaged/melted/plugged up cat(s) behind your engine? Q: Do you ever remember seeing a flashing SES light
while driving? This would further support the melted cat/plugged up exhaust theory.

****

But if we don't have that list of DTCs, I'm reduced to conjecture.

But if you and your local support team are convinced that you have good Spark + Fuel + Compression, but it
won't run right, AND you haven't already dropped the exhaust, then that's were I'd go next. Don't know if I'd
bet a steak dinner on it, but with a plugged exhaust it *is* possible to experience symptoms like you describe.

I know just how frustrating this can become. But if we approach this with an incremental Building Block approach
(ie: assume everything is BAD, and step by step prove each subsystem is good) ...eventually it will run again.

For once you have the internal combustion triad combined, it *has* to run:

xc_hide_links_from_guests_guests_error_hide_media

:0)

Especially if you still have cats, drop the exhaust & see what happens. Fingers crossed
you find the answer asap.

Best of luck. And let us know what you discover --

Some of your symptoms sound to me, like a failing IACV and/or fuel pump relay. The fuel pump relay can be checked one of two ways: is it overly warm, moreso than the other relays...or swap another 5 pin relay from a known good system into the fuel pump relay socket. Fuel pump relay is around $10 at most parts stores. Bad idle air control valve will create all kinds of havoc, BTDT with my truck recently.
And double check for restrictions in the cats, rest of exhaust, and fuel system. Does not take long for bad gas to clog a fuel filter.....

 

[kgault]

any luck? was it fuel pump? sounds like you're having a similar issue to me

 

[SuperSpore]

Greetings from the other side of the pond. According to the FSM the Passlock security feature exerts
it's no start control via telling the VCM whether or not to drive or disable the actual fuel injectors. (See attached.)

I think this is the only area disabled, for I can't find any mention of the Ignition in this section of the book.

And the theory that the Fuel Pump Relay is deactivated by the Passlock would not result in positively killing the engine
if the keys don't match. Because if the thief cranks the engine long enough, the oil pressure will get above the 4 psi
threshold, and the fuel pump would receive power from this redundant power path, & then the truck would still start. (!)




You wouldn't happen to have written down a list of all the codes you cleared? This could give us important clues
as to where we should look next in order to fix whatever is left. (On big multi-faceted problems like this, you can
never have too much failure context.)

****

Let's give some thought to what has & hasn't been tried to date, and see if anything comes to mind.

Forgetting computers for a moment, back in the carburetor days I could have a bowl full of fuel, the accelerator
pumps are shooting like they are supposed to, the gasoline is known good, the choke isn't stuck closed, etc.
And the dizzy is throwing good sparks towards each of the plugs in the correct sequence. Plenty of parts have
been substituted with no change in behavior.

But if unbeknownst to me some prankster had stuffed a potato up the tailpipe, you can get that barely starts,
runs for a second or two, struggling to run, and dies -- even though all the normal no-start stuff has been
checked & rechecked. (TBI analog: Engine doesn't track VE tables due to inability to breathe because of brick wall EGR.)

****

Coming full circle, if you had a bunch of 'O2 too rich' or P0300 / P030x DTCs in the history list, and the root cause(s)
of these issues have since been since cleared, then we could infer that there's a good chance that you have a
damaged/melted/plugged up cat(s) behind your engine? Q: Do you ever remember seeing a flashing SES light
while driving? This would further support the melted cat/plugged up exhaust theory.

****

But if we don't have that list of DTCs, I'm reduced to conjecture in public. Not my strong suit.

But if you and your local support team are convinced that you have good Spark + Fuel + Compression, but it
won't run right, AND you haven't already dropped the exhaust, then that's were I'd go next. Don't know if I'd
bet a steak dinner on it, but with a plugged exhaust it *is* possible to experience symptoms like you describe.

I know just how frustrating this can become. But if we approach this with an incremental Building Block approach
(ie: assume everything is BAD, and step by step prove each subsystem is good) ...eventually it will run again.

For once you have the internal combustion triad correct, it *has* to run:

xc_hide_links_from_guests_guests_error_hide_media

:0)

Especially if you still have cats, drop the exhaust & see what happens. Fingers crossed
you find the answer asap.

Best of luck. And let us know what you discover --

Greetings from the other side of the pond. According to the FSM the Passlock security feature exerts
it's no start control via telling the VCM whether or not to drive or disable the actual fuel injectors. (See attached.)

I think this is the only area disabled, for I can't find any mention of the Ignition in this section of the book.

And the theory that the Fuel Pump Relay is deactivated by the Passlock would not result in positively killing the engine
if the keys don't match. Because if the thief cranks the engine long enough, the oil pressure will get above the 4 psi
threshold, and the fuel pump would receive power from this redundant power path, & then the truck would still start. (!)




You wouldn't happen to have written down a list of all the codes you cleared? This could give us important clues
as to where we should look next in order to fix whatever is left. (On big multi-faceted problems like this, you can
never have too much failure context.)

****

Let's give some thought to what has & hasn't been tried to date, and see if anything comes to mind.

Forgetting computers for a moment, back in the carburetor days I could have a bowl full of fuel, the accelerator
pumps are shooting like they are supposed to, the gasoline is known good, the choke isn't stuck closed, etc.
And the dizzy is throwing good sparks towards each of the plugs in the correct sequence. Plenty of parts have
been substituted with no change in behavior.

But if unbeknownst to me some prankster had stuffed a potato up the tailpipe, you can get that barely starts,
runs for a second or two, struggling to run, and dies -- even though all the normal no-start stuff has been
checked & rechecked. (TBI analog: Engine doesn't track VE tables due to inability to breathe because of brick wall EGR.)

****

Coming full circle, if you had a bunch of 'O2 too rich' or P0300 / P030x DTCs in the history list, and the root cause(s)
of these issues have since been since cleared, then we could infer that there's a good chance that you have a
damaged/melted/plugged up cat(s) behind your engine? Q: Do you ever remember seeing a flashing SES light
while driving? This would further support the melted cat/plugged up exhaust theory.

****

But if we don't have that list of DTCs, I'm reduced to conjecture in public. Not my strong suit.

But if you and your local support team are convinced that you have good Spark + Fuel + Compression, but it
won't run right, AND you haven't already dropped the exhaust, then that's were I'd go next. Don't know if I'd
bet a steak dinner on it, but with a plugged exhaust it *is* possible to experience symptoms like you describe.

I know just how frustrating this can become. But if we approach this with an incremental Building Block approach
(ie: assume everything is BAD, and step by step prove each subsystem is good) ...eventually it will run again.

For once you have the internal combustion triad correct, it *has* to run:

xc_hide_links_from_guests_guests_error_hide_media

:0)

Especially if you still have cats, drop the exhaust & see what happens. Fingers crossed
you find the answer asap.

Best of luck. And let us know what you discover --

20 years ago I was a lot younger, splitting my free time between lashing my new gsxr 1000, and researching design defects & upgrades on that one crazy Suzuki forum that became infamous for attracting unsavory characters.
In that place there were as many knowledgeable contributors, (some of which were aerospace engineers who I learned a lot from) as there were aggressive condescending know it all's that were less than helpful - (admittedly maybe some squids deserved that type of response).

My point is, this is one of those responses that are few and far between both in clarity of logic and patience, which we will all need at some point.
Especially when we're in over our heads and frustration starts to take hold. Like Socrates said: "The more I know, the more I realize I know nothing."
I hope OP appreciates your response as much as I do.

 

[Pinger]

Like Socrates said: "The more I know, the more I realize I know nothing."

Some years later... Freud said: ''Stare at the facts and the truth will emerge''. It's as if Freud knew we'd have GMT400s long before they existed.

 

[Wademo]

I have read this from the beginning, so I apologize if I missed it, but did he try running it with the MAF sensor unplugged?