major problem...real headscratcher

[matts]

ok, here's the deal. wife's 99 SE with 2.4/auto. i dont know where to start....

well it's missing in cylinders 1 and 4 at the same time.

fuel pump is working right.

fuel filter is new.

checked the coils with another 2.4 motor and no matter what we replaced from one to the other as far as coil or module thing it always missed on 1 & 4. so i'm going to say we can eliminate the ignition under the silver part with "2.4" under it.

:lol: sorry for the non-technical words right now. i've been up since yesterday afternoon.

scanner shows the injectors are working right.

spark plugs only have about 25,xxx miles on them. so they're used, but when they're supposed to last 100,000 miles they dont have many miles on them. not to mention, what are the odds of 2 plugs going bad at the same time?

the only code showing up is "301" i believe. it was mutliple misfire detected' or something.

---------------

now for what happened:

about a month ago the car started running like it had water in the fuel. just every now and then it'd sputter, but go on. it's gotten worse as of lately. i ran 2 tanks of gas through it with Heet and fuel injector cleaner through it...hoping that might clear it up a little bit, but with no luck.

it seemed to "miss" when you had a load on the motor. like going uphill, or just mashing the gas moderately. let off the gas and it would act fine, or give it a little bit of gas and it'd work great. only when under a load would it act funny.

the other night i was headed to work...about a 20 mile trip. made it to roughly mile 16, made a right hand turn onto another road, gave it some gas to speed up (not a bunch like i was in a race, but enough to make the car kick down a gear) and it just fell flat on it's face. starting missing REAL bad. i limped it to work and thought maybe it would run it's course and be better in the morning.

went out the next morning, started it up and it was running worse. almost to the point of not running. i sat there for a minute comtemplating what i was gonna do. i decided not to get a tow bill if i didn't absolutely have to, so i drove it to my mechanic. put it in reverse and it almost died. got it limped out of the parking lot and it seemed that when the car hit ~2000 rpm the car would straighten up and run fine, but slow down and it done the same thing as before. on the way to the shop the car warmed up (naturally) and seemed like once it got to operating temp it ran a little better.

we're scratching our head wondering what it might be. only other thing we can think of is the computer. that's where i'm hoping some of you brilliant minds come in and help me out.

[rixGAphx]

Sounds exactly like a bad Fuel Pressure Regulator.
It has one pressure setting for idle and low pm, another for higher rpm (2500+, IIRC).
At idle and low throttle, the high vacuum (in the intake manifold) sucks against the FPR's internal diaphragm, and holds the pressure at about 34 psi.
When the throttle opens more, indicating you want more air AND fuel, then the vacuum drops and the FPR raises the pressure to about 45 psi.

Too much fuel (high pressure at low throttle) or too little fuel (low pressure at higher throttle) will cause the misture to be rich or lean, respectively.
This results in a 'misfire', just the same as lack of spark.

P0300 = Multiple/random misfire.
P0301 = Misfire detected, cylinder #1.
P030x = Misfire detected in cylinder 'x'.

If I were you, I would check the fuel pressure, and the operation of the FPR.

Hope this helps,
-Rick

[matts]

i'll check that, but isn't it odd that it only gets a misfire in 1 & 4? 2 & 3 are working flawlessly.

i dont remember the code number, i thought he said it was mulitple misfire.

is it possible it's in the computer? or if it's not the FPR what would you check next?

[Matt95GT]

I wouldn't do anything else until you change the plugs.

[matts]

i'll pull them off, but do you really think it's possible for 2 plugs to go at once like that? i guess if they did i have more serious problems than i want to deal with

[rixGAphx]

is it possible it's in the computer?
or if it's not the FPR what would you check next?Well, if you haven't pulled the plugs, definitely check them and the boots that serve as their wires.

Not likely it's the computer.
GM got things right with their little black boxes.
These things are durable-as-hell, and I wold try EVERYTHING else before even thinking of the PCM.

Especially since it's the little black box that is accurately TELLING you that you have a misfire.

Good luck,
-Rick

[rixGAphx]

i'll pull them off, but do you really think it's possible for 2 plugs to go at once like that? i guess if they did i have more serious problems than i want to deal withYou're misunderstanding the GA's style of ignition.
The coil delivers a 'waste spark' to the 'other' cylinder at the same time that it's sparking the powerstroke.

Everytime a plug fires, an identical (but opposite) 'spark' is going to its paired companion plug, whose piston is at the top of its exhaust stroke.
When one plug 'mis-fires', regardless of the cause, then its companion plug *may* also misfire on the ITS next stroke, becasue most of the spark engergy is going thru the fouled (not broken) companion plug.
Or the engine's sensors (which are actually primitive and stupid) may *think* there's been a misfire and report it as such, even though there were 300 misfires in #1 and only 3 misfires in #4 (per 1500 revolutions, or whatever).

This isn't serious, it's a simple misfire or two.
Every friggin' car has been misfiring since before Henry's first Model T.
Analyze and fix.

[Matt95GT]

i'll pull them off, but do you really think it's possible for 2 plugs to go at once like that? i guess if they did i have more serious problems than i want to deal with

Not likely, but the 2.4 (and 2.3) ignition systems uses a 2-coil "waste spark" configuration. Cyl 1 and 4 are on the same coil... the IDI module / PCM has no way on know if cyl 1 or 4 or both are at fault.

Edit: Rick is always about 1 minute ahead of me :lol:

[Montrealgrandam]

try to swap the plugs if your there! #2 in #1 and #3 in #4

[matts]

hmm, i'll check the plugs in the morning then.

[Igor Gavric]

Couldn't the coilpack for cylinders 1 & 4 be at fault for this?
Check spark see if its bright blue/white or orange?
Orange = Weak coil
Bright blue/white = I hope you weren't holding on to it...

[Matt95GT]

Couldn't the coilpack for cylinders 1 & 4 be at fault for this?
Check spark see if its bright blue/white or orange?
Orange = Weak coil
Bright blue/white = I hope you weren't holding on to it...

Could be. Or anything else in the somewhat-touchy IDI system.

Can't really do that on a 2.3/2.4... no plug wires, system won't operate with cover off.

[kyboman]

A scanner can't tell if the injector is sticking. It only reads the resistance.
Try tapping on the injector. If the misfire stops, change the injector.

[matts]

THINK i got the problem narrowed down. i say think because i haven't got the new parts on yet to see.

but i swapped the plugs and boots on 1 & 2 and the misfire changed with it. on the 3 & 4 i think i changed them twice on accident. so in other words i think they ended back up with in the same spot they came out of :lol: i was trying to do a couple of other things at once and got called away right after i got them taken out. but the misfire stayed in 4.

so i ordered new boots and plugs from pontiac (actually just the boots, they had plugs in stock), but one of the boots didn't come in. supposed to be here monday morning, so after i get off i'm gonna change everything out and see if that fixes it.

i don't get it though. the plugs aren't that old, and they looked pretty good.

[matts]

update:

went and changed plugs from 1 to 2 and 3 to 4. problem stayed on 4, but moved to 2 instead of 1. thought ok...maybe it's in the plugs and boots, because i wasn't 100% sure i changed 3 to 4. thought i might have accidentally put them back in the same hole.

went and bought new plugs and boots $50. put them in, fired it up and it purred like a kitten..........until i gave it gas. spit and sputtered like it was doing. rev it up to around 3,000rpm and it smooths out.

now we're going to try injector in #4 and see where we're at when the smoke clears. then we'll move through the injectors 1 at a time. we'll get to the problem eventually. hopefully i wont be TOO far in the hole when we find it thought :lol:

[Brad97GS]

I noticed that you replaced the boots. What about the coil housing?

[Pontiac]

Bright blue/white = I hope you weren't holding on to it...

I couldn't help but laugh... I'd be the moron that does this... twice.. intentionally. {chuckle}

[matts]

I noticed that you replaced the boots. What about the coil housing?

changed all the stuff under the "2.4" piece of metal with one he had in his shop. problem stayed the same

[Matt95GT]

changed all the stuff under the "2.4" piece of metal with one he had in his shop. problem stayed the same

Hmm. A couple thoughts...
1. Make certain that connector to the IDI module is completely secure, maybe remove that rubber gasket in the plug, wiggle around, etc. That plug gave me trouble already, and was just an intermittent loose connection. Zip tie + new plug gasket solved it.

2. I would use a multimeter and check the ground and reference voltages at the MAP and TPS. Also check the output of the TPS for jumps or dead spots.

[matts]

Hmm. A couple thoughts...
1. Make certain that connector to the IDI module is completely secure, maybe remove that rubber gasket in the plug, wiggle around, etc. That plug gave me trouble already, and was just an intermittent loose connection. Zip tie + new plug gasket solved it.

2. I would use a multimeter and check the ground and reference voltages at the MAP and TPS. Also check the output of the TPS for jumps or dead spots.


i'll check that.


but update: replaced the #4 injector and *drum roll please*..........didn't fix it. STILL missing #2 and #4.

now it's throwing P01621....suspect faulty PCM :(

called the pontiac dealer and priced a new PCM.......$530 plus they need to flash it to the car. so i figure $750 after everything is said and done. i'm trying my hardest not to sink this much into the car. i'm already $200 in the hole on parts that didn't work


i'm gonna give pontiac dealer a call monday and see if there's a way they can test the computer if i take it out

[rixGAphx]

P1621 = Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match
Might be the PCM itself, or it might need a re-flashing; I dunno diddly about that.
I think a sophisticated scanner, as used at the dealership, can 'see' inside the PCM real-time as it's operating, and possibly determine wha portion might be inoperable. But this is a very limited understanding on my part, based solely on reading previous posts on this board.

'Guaranteed Used' PCM's are available from various ebay dealers at much more reasonable cost than new; really, they're qite dependable as long as they came from a car of the exact same year/model/engine.
Mebbe one of those vendors can tell you how to analyze your PCM?

Good luck,
-Rick

[matts]

P1621 = Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match
Might be the PCM itself, or it might need a re-flashing; I dunno diddly about that.
I think a sophisticated scanner, as used at the dealership, can 'see' inside the PCM real-time as it's operating, and possibly determine wha portion might be inoperable. But this is a very limited understanding on my part, based solely on reading previous posts on this board.

'Guaranteed Used' PCM's are available from various ebay dealers at much more reasonable cost than new; really, they're qite dependable as long as they came from a car of the exact same year/model/engine.
Mebbe one of those vendors can tell you how to analyze your PCM?

Good luck,
-Rick

yeah, i called the dealer and asked them about checking the PCM to make sure it was all good. the guy on the other end didnt' know what i talking about (maybe a temp) but said i could bring it in friday and they could check the codes. i thought dang, i dont want to give you $100 to tell me the codes i already know about.

i'm gonna have to stop by there and talk to someone face to face i guess.


oh i've already thought about finding a computer from a junk yard. my butthole drew up when they told me what they wanted for a new computer

[Matt95GT]

The dealer sounds incompetent... I wouldn't go there. $750 later you may have the same problem. I'd grab a used PCM from a junk yard or parts locater service. Keep in mind it will have to be a 99 LD9 PCM... other years will not work as they switched to high impedance injectors in 2000.

[matts]

The dealer sounds incompetent... I wouldn't go there. $750 you may have the same problem. I'd grab a used PCM from a junk yard or parts locater service. Keep in mind it will have to be a 99 LD9 PCM... other years will not work as they switched to high impedance injectors in 2000.

the dealer is usually pretty good, i was on a cell phone too, might have had something to do with it.


what about having it flashed to my VIN? a necessity?

[Matt95GT]

Some of the 99+ experts may have to chime in, but as I recall most people who buy those reprogrammed performance ECU's all have the wrong VIN. Unless you're in an area with emissions testing that requires ECU VIN matches, I wouldn't care much about that. And even if you do, temporarily using another ECU would be helpful for troubleshooting.

[rixGAphx]

Some of the 99+ experts may have to chime in, but as I recall most people who buy those reprogrammed performance ECU's all have the wrong VIN. Unless you're in an area with emissions testing that requires ECU VIN matches, I wouldn't care much about that. And even if you do, temporarily using another ECU would be helpful for troubleshooting.I think he means, "If I buy another PCM, either brand-new or j/y, and install it in my car, must I then tow the car to a GM dealer, empty my wallet, and have them do some sort of 'computer-flash' black magic for the replacement PCM to communicate and operate properly?"

I don't know the answer.
When it comes to computers, if turning a balky one off-on doesn't fix the ailment, then I'm up a creek.

-Rick

[matts]

went by and talked to the dealer today. they said they highly doubted the computer was totally shot, said it just hardly happens.

i asked them about their $70 diagnosis. told them i didn't want to pay $70 and them just give me a list of codes i already have. they said with that $70 they did more than just scan it, and they were pretty sure they could track the problem down. and then if it was something i let them fix that $70 would go toward the price of fixing it.

[b0ogeyman]

went by and talked to the dealer today. they said they highly doubted the computer was totally shot, said it just hardly happens.

i asked them about their $70 diagnosis. told them i didn't want to pay $70 and them just give me a list of codes i already have. they said with that $70 they did more than just scan it, and they were pretty sure they could track the problem down. and then if it was something i let them fix that $70 would go toward the price of fixing it.

ummm yeah thats exactly what they told me too , gave me a ride back home called me two hours later to tell me oh yeah you got 107 and 341 !!!!! which i already have had mentioned before to them !!!!!

they did not lie either about adding my diagnostic charge towards the repair but again they wanted $650 for changing two sensors that were $150 at Autozone i changed them my self 2 bolts and couple of clamps took m e 15 min total !

turned out that wasnot my problem but that what the dealer said too we want the $650 before we even touch anything else and we dont guarantee its gonna fix the problem but it would get us closer !

end of the story i paid them for the test they did after a 50% discount from the manager i guess after i complained for him about what happened came to $40 or so for nothing.

[matts]

ummm yeah thats exactly what they told me too , gave me a ride back home called me two hours later to tell me oh yeah you got 107 and 341 !!!!! which i already have had mentioned before to them !!!!!

they did not lie either about adding my diagnostic charge towards the repair but again they wanted $650 for changing two sensors that were $150 at Autozone i changed them my self 2 bolts and couple of clamps took m e 15 min total !

turned out that wasnot my problem but that what the dealer said too we want the $650 before we even touch anything else and we dont guarantee its gonna fix the problem but it would get us closer !

end of the story i paid them for the test they did after a 50% discount from the manager i guess after i complained for him about what happened came to $40 or so for nothing.

trust me, it's not money i'm eager to spend, but i'm at a dead end. i can either a.) start sinking money into that more than likely isn't going to help or b.) give them some money and hopefully open up a new road or 2.

[csthews]

Sounds exactly like a bad Fuel Pressure Regulator.
It has one pressure setting for idle and low pm, another for higher rpm (2500+, IIRC).
At idle and low throttle, the high vacuum (in the intake manifold) sucks against the FPR's internal diaphragm, and holds the pressure at about 34 psi.
When the throttle opens more, indicating you want more air AND fuel, then the vacuum drops and the FPR raises the pressure to about 45 psi.

Too much fuel (high pressure at low throttle) or too little fuel (low pressure at higher throttle) will cause the misture to be rich or lean, respectively.
This results in a 'misfire', just the same as lack of spark.

P0300 = Multiple/random misfire.
P0301 = Misfire detected, cylinder #1.
P030x = Misfire detected in cylinder 'x'.

If I were you, I would check the fuel pressure, and the operation of the FPR.

Hope this helps,
-Rick

So, have you checked the FPR yet? I had a similar problem on my car. After nearly $1000 in parts and labor for ignition coils, plugs, boots, IAC, fuel filter, etc. I gave up on the NAPA-certified mechanics. After about 10 minutes of looking around, I pulled the vacuum cable off the top of the FPR, revved the engine, and watched the gas squirt out (leaking FPR diaphragm). Replaced the FPR and everything runs fine.

[matts]

yeah, checked it already.

[b0ogeyman]

trust me, it's not money i'm eager to spend, but i'm at a dead end. i can either a.) start sinking money into that more than likely isn't going to help or b.) give them some money and hopefully open up a new road or 2.

wow matts you sound depressed for real , well if thats the case take it to the dealer after all they are the ones who KNOWS really this car , i was just telling you my experience with them was not really good just so you wouldn't put hopes that they gonna REALLY do a check on that problem for just $70!!!!

i read through your thread and of the complications that you got in there the dealer not gonna help you a bit for that 70$.

i had a misunderstanding on how that $70 check work , a regular mechanic shop would want $70 an hour to check and they would tell you we dont know how long its gonna take us , so i though they say dealers cost more?! not really they are charging me a FLAT fee to figure out my problem wohooo yaaayy awsome.

indeed dealers cost more... that $70 for them to get someone to plug thier scanner and read your codes!!!

just my experience after all thought i would share .

[matts]

wow matts you sound depressed for real , well if thats the case take it to the dealer after all they are the ones who KNOWS really this car , i was just telling you my experience with them was not really good just so you wouldn't put hopes that they gonna REALLY do a check on that problem for just $70!!!!

i read through your thread and of the complications that you got in there the dealer not gonna help you a bit for that 70$.

i had a misunderstanding on how that $70 check work , a regular mechanic shop would want $70 an hour to check and they would tell you we dont know how long its gonna take us , so i though they say dealers cost more?! not really they are charging me a FLAT fee to figure out my problem wohooo yaaayy awsome.

indeed dealers cost more... that $70 for them to get someone to plug thier scanner and read your codes!!!

just my experience after all thought i would share .


not so much depressed as aggrevated with it. not to mention i've worked hard to keep miles off my trailblazer. with her car in the shop she's driving the trailblazer.....and racking up the miles nicely on it.

and if i hand them $70 and they DON'T tell me what wrong with it me and the service manager are going to have words. he was standing there the other day when i went in and said they would be able to tell me exactly what's wrong ;)

[RACHEL]

Hey Did You Get Anywhere? I Seem To Be Having A Similar Prob I Hope You Got It Going. We're Taking The Coil Pack Apart To Analyze As I'm A Little Further In Than You With Replacement Parts. Good Luck!

[Shadow-D]

Yea I'd like to hear what the out come is.....

[matts]

still gotta take it to the dealer. everytime i have a free chance i can't get it in. with all my stuff in there i'm not too wild about taking it up there and leaving it.


still nothing new at this point