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Premium Member
2003 Cadillac Seville STS
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Discussion Starter #41
From a service writer at Fitzgerald Cadillac about 13 years ago. The build sheets used to be part of the old GM VIS data system and were free for the asking.
So I saw something interesting in the freeze frame just now on my scan tool for P0300. I see in the freeze frame the afr is 9.5:1. Why the hell would it do that?
581582
 

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2003 Cadillac Seville STS
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Discussion Starter #43
Have we been into the individual fuel injector electrical connectors and the FPR (Fuel Pressure Regulator) yet ??

EDIT: 9.5:1 is 30% away from the ideal of 14.7:1.

No we haven’t. Well I checked both wires too the injector from the pcm and from the injector to the fuse box and they both turned out good. I haven’t done too much of a check on the fpr but I do remember disconnecting the vacuum hose on it while idling for like 10 seconds a while ago and didn’t see any fuel coming out
 

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White Diamond '03 DHS (with DTS floor shift)
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I haven’t done too much of a check on the fpr but I do remember disconnecting the vacuum hose on it while idling for like 10 seconds a while ago and didn’t see any fuel coming out
That would indicate that the FPR is good.
 

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2003 Cadillac Seville STS
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Discussion Starter #45
That would indicate that the FPR is good.
I’m gonna do a fuel pressure test as soon as I get the adapter for the scrader valve apparently my 60 dollar fuel tester kit with the 15 adapters didn’t come with one lol. What would you do after that?
 

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2003 Cadillac Seville STS
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Discussion Starter #46

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White Diamond '03 DHS (with DTS floor shift)
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I’m gonna do a fuel pressure test as soon as I get the adapter for the scrader valve apparently my 60 dollar fuel tester kit with the 15 adapters didn’t come with one lol. What would you do after that?
Not sure at this point. This one's a real stumper.
 

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2003 Cadillac Seville STS
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Discussion Starter #48
Not sure at this point. This one's a real stumper.
It really is isn’t it? I’ve learned so much working on this issue but I just want it fixed now. The guy at the dealer entered my vin number and said that recall had been fixed on my car. Anywhere I can check that? Because I thought they put some sticker near the radiator support or the strut towers. Do you have one? Maybe I’ll check the main pcm ground. I think if I remember right it’s G106. That’s the only other thing I can think of. BUT for some reason the computer is flooding the crap out of the motor on cold start giving it a 9.5:1 afr... I think it chooses that from the table using the MAF, ECT, and MAP correct? It seems to have started after I messed around the MAF area but all I did was clean it and I used the correct MAF cleaner from CNC
 

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White Diamond '03 DHS (with DTS floor shift)
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I thought they put some sticker near the radiator support or the strut towers. Do you have one?
No, my PCM was never replaced. Either my car did not fall in the VIN range or the recall was issued after my warranty expired. I only took it in to a dealer for warranty work. Either way, I've never had a problem with the PCM.


BUT for some reason the computer is flooding the crap out of the motor on cold start giving it a 9.5:1 afr... I think it chooses that from the table using the MAF, ECT, and MAP correct?
I believe that is correct.


It seems to have started after I messed around the MAF area but all I did was clean it and I used the correct MAF cleaner from CNC
That's a big clue. Might want to check your work. If nothing is amiss, it might be worth a try replacing the MAF sensor. Save some money and get one from the Men's Mall just in case that's not the problem. That said, the MAF is monitored and SHOULD trip the MIL and set a DTC if it is bad.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Your MAF work - did you install the intake duct resonator correctly - ANY air leak where that useless resonator mounts to the duct gives an incorrect airflow signal. Do the Butt Plug modification. It's a 2" PVC pipe cap from any hardware store, with a coolant hose band clamp. Secure the PCM cover with a machine screw from your possibles box. The modification sure makes underhood checks easier .......

The ignition signal loss recall - my car was done - I have the dealership work invoice - but the only sticker in the engine compartment is for the fuel tank pressure sensor recall and that's on the water pump belt safety shroud. Campaign 03038.

There's no sticker on the PCM or on the PCM box.

Butt plug & air box 2 notes.JPG
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Maybe you knocked one of those tiny heated resistors loose ......... or damaged the IAT. That's a 5-pin connector. Wiring fault ?

MAF end view.jpg
MAF front quarter.jpg
 

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2003 Cadillac Seville STS
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Discussion Starter #52 (Edited by Moderator)
Your MAF work - did you install the intake duct resonator correctly - ANY air leak where that useless resonator mounts to the duct gives an incorrect airflow signal. Do the Butt Plug modification. It's a 2" PVC pipe cap from any hardware store, with a coolant hose band clamp. Secure the PCM cover with a machine screw from your possibles box. The modification sure makes underhood checks easier .......

The ignition signal loss recall - my car was done - I have the dealership work invoice - but the only sticker in the engine compartment is for the fuel tank pressure sensor recall and that's on the water pump belt safety shroud. Campaign 03038.

There's no sticker on the PCM or on the PCM box.

View attachment 581761
Sorry about the late response. I’ll check the MAF again but I will check that ugly resonator too. I’ll replace it because it seems pointless and it’s very annoying to put back on. I’ve taken it off and on a million times since I had this issue but I’ll check.

Maybe you knocked one of those tiny heated resistors loose ......... or damaged the IAT. That's a 5-pin connector. Wiring fault ?

View attachment 581762 View attachment 581763
Btw I got 42 psi engine off turning the key for fuel pressure
 

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2003 Cadillac Seville STS
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Discussion Starter #56 (Edited by Moderator)

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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In your MAF pictures - where are the 3 tiny heated resistors that send the correct airflow signals to the PCM? See my MAF post. Leave that resonator on the garage shelf.

How often do you need to add coolant to keep it at the correct cold level? There's a FULL COLD legend and flat arrow molded into the top and side of the surge tank.
 

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2003 Cadillac Seville STS
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Discussion Starter #58
In your MAF pictures - where are the 3 tiny heated resistors that send the correct airflow signals to the PCM? See my MAF post. Leave that resonator on the garage shelf.

How often do you need to add coolant to keep it at the correct cold level? There's a FULL COLD legend and flat arrow molded into the top and side of the surge tank.
The three resistors are there. You can see on each one part of the thin wire is hanging over where it connects on I’m assume that’s normal because it’s on all of them. They all look clean.

Not very often at all. I haven’t driven it much recently but it’s about an inch down from the full cold mark but it’s taken a good amount of time to go down to that spot. Not sure of the condition of the water crossover gasket. I bought fel pro calve cover kit and crossover gasket set as well as a new water pump with all new oem delco plugs and denso boots
 

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2003 Cadillac Seville STS
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Discussion Starter #59
In your MAF pictures - where are the 3 tiny heated resistors that send the correct airflow signals to the PCM? See my MAF post. Leave that resonator on the garage shelf.

How often do you need to add coolant to keep it at the correct cold level? There's a FULL COLD legend and flat arrow molded into the top and side of the surge tank.
So I went on the highway and put her in second and redlined 1st and second a couple times and drove up a long hill. Didn’t go past halfway but when I got back I Parked it and immediately slowly backed off the surge tank cap and depressurized the system so now I’ll see how it starts tonight or tomorrow
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Please be careful when you open the surge tank cap after any sort of driving. If the car has been run hard there's a LOT of heat built up in the reciprocating machinery - the stuff that coolant never touches - and, as it passes off that heat to the block/coolant it's possible that the coolant could warm to a boil point at atmospheric pressure. What cools all the engine guts ? Engine oil - properly operating - it runs at 190 - 220 degrees. Our engines overheat at 270 degrees - and then go into Camel Mode.

Coolant Boiling point.jpg


Note that the recommended 50/50 mix line is out of sequence. Your car uses an 18 psi pressure cap, so do some extrapolation.
 
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