Cadillac Owners Forum banner

1 - 20 of 23 Posts

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #1 (Edited)
I'm trying to solve an idle issue and cleaned my IAC with brake cleaner, then learned I should have used electronic cleaner.
I still throw P0300. Should I replace the IAC?
So far I've cleaned the throttle body, checked the EGR, checked plugs and boots. Replaced both coils paks. Replaced fuel filter. I think pressure is good, it runs strong on the highway with no hesitation and lots of get up. I've done the WOT procedure.
Vacuum sucks at about 12 and not steady. New boot coming in.
Anything else I can check? It's an 02 Eldorado ETC with 55k miles.
Thanks,
Taz
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,504 Posts
What new boot ? Remove the beauty cover and trace out/verify integrity for all the vacuum lines that come off the throttlebody and run to several pieces of powertrain control and emissions equipment.

If a plastic vacuum pipe/elbow/connector(s) is broken they can be replaced with a suitable length of proper sized vacuum tubing from the Help! racks at large parts stores.

You don't want to have to buy a new IAC - it takes deep pockets.........

Eldorado ETC = Eldorado Eldorado Touring Coupe.:lildevil:
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #3
What new boot ? Remove the beauty cover and trace out/verify integrity for all the vacuum lines that come off the throttlebody and run to several pieces of powertrain control and emissions equipment.

If a plastic vacuum pipe/elbow/connector(s) is broken they can be replaced with a suitable length of proper sized vacuum tubing from the Help! racks at large parts stores.

You don't want to have to buy a new IAC - it takes deep pockets.........

Eldorado ETC = Eldorado Eldorado Touring Coupe.:lildevil:
Yeah, Yeah, yeah...I know. Just realized it. :banghead: The others are just Eldorados. I guess I'm used to that.:D:D:D

Boot? I mean the intake manifold rubber boot from the TB.

I tested every vacuum line and diaphram with a Mityvac. Man, I should have bought one of those years ago. I also learned there is such a things as a vauum check valve (to the A/C ducts).
My EGR was dirty, but the "pintle??" moved freely.
Taz
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,286 Posts
I'm trying to solve an idle issue and cleaned my IAC with brake cleaner, then learned I should have used electronic cleaner.
I still throw P0300. Should I replace the IAC?
So far I've cleaned the throttle body, checked the EGR, checked plugs and boots. Replaced both coils paks. Replaced fuel filter. I think pressure is good, it runs strong on the highway with no hesitation and lots of get up. I've done the WOT procedure.
Vacuum sucks at about 12 and not steady. New boot coming in.
Anything else I can check? It's an 02 Eldorado ETC with 55k miles.
Thanks,
Taz
------------------------
Should I replace the IAC
NO - IAC is the Idle Air Control solenoid - and will NOT cause - or cure - a misfire -

I still throw P0300
that means you still have a misfire - somewhere -

P0300 is a generic misfire code - usually no spark - could also be no gas -
our on-board code readers will not display WHICH cylinder/cylinders is/are misfiring -
only that there IS a misfire -

take the car to any large auto parts store - they will check your codes for free -

P0301 is a misfire in cylinder #1 - P0302 is cylinder #2 - P0303 is #3 - etc -

once you discover WHICH cylinder is misfiring - diagnosis becomes much easier -
-----------
Replaced fuel filter. I think pressure is good,
what is the fuel pump pressure at the fuel rail - should be right around 45PSI -

use a stethoscope - or a long handle screwdriver and listen to each fuel injector -
each one should have a strong "clicking" sound with the engine running -
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #6
------------------------
Should I replace the IAC
NO - IAC is the Idle Air Control solenoid - and will NOT cause - or cure - a misfire -

I still throw P0300
that means you still have a misfire - somewhere -

P0300 is a generic misfire code - usually no spark - could also be no gas -
our on-board code readers will not display WHICH cylinder/cylinders is/are misfiring -
only that there IS a misfire -

take the car to any large auto parts store - they will check your codes for free -

P0301 is a misfire in cylinder #1 - P0302 is cylinder #2 - P0303 is #3 - etc -

once you discover WHICH cylinder is misfiring - diagnosis becomes much easier -
-----------
Replaced fuel filter. I think pressure is good,
what is the fuel pump pressure at the fuel rail - should be right around 45PSI -

use a stethoscope - or a long handle screwdriver and listen to each fuel injector -
each one should have a strong "clicking" sound with the engine running -
I should have mentioned, I hooked up my computer, ran scans wtih 2 different software, did data capture. P0300 only, no freezframe data available, no 301,302 etc. Took it to Oreilly and had them do the same. P0300 only.
My ECU is not an extended ODBII data set. It's the generic, government issued OBDII dataset which surprised me a bit. So no sub sets or Cadillac/N* specific codes.
Thanks for the ehlp,
Taz
Injectors were tested, 12-12.2 ohms across all 8. Good sound. Wiring was shorted on #4 but fixed.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,504 Posts
You asked about the "plenum", that oddball GM name for the rubber/steel connector between the throttlebody and intake manifold.

Assuming this is for the 2002 Eldorado, click my username, open the profile. Left column, lower part - 2 albums, 6 pages of parts for your engine. MANY pictures and diagrams of the throttlebody, plenum, intake manifold, associated equipment.
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #8
Thanks Submariner,
I have browsed your gallery before. Good stuff.
In a sudden moment of clarity (someone hit me over the head) LOL. My issue is all from the vauum leak.
This morning I re-tested the vacuum lines. Instead of each line and component, I did it from the TB connections. When I got to the line that went to the FPR, I had the duh moment. Not enough vaccum at idle due to the plenum leak...Duh!
I replaced my IAC and ERG. I broke my IAC trying figure out how it worked. LOL. That plastic pience in the middle gets brittle over time and with heat. It would have gone soon.
When the intake parts get in, I should be good to go.
I do have one question though, Should I be able to draw more than 17in Hg on the brake booster?
Thanks,
Taz
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,792 Posts
17 in Hg is about right and will be the same no matter where you take the reading.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,504 Posts
In my 2002 Seville idle vacuum is about 22", high speed coastdown is about 28", highway depends on road and load, but varies between 18" - 14", WOT redline is about 0.5" - 1".

MAP reads out in inverse vacuum units from 0 - 14.8, so a MAP of 5.0 = -10 = 20" of manifold vacuum. (Vacuum is usually expressed in units from 30" - 0".)

........ and, as always, atmospheric pressure (14.7 psi at sea level) pushes into a vacuum - the engine does not "suck in" air.
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #12
In my 2002 Seville idle vacuum is about 22", high speed coastdown is about 28", highway depends on road and load, but varies between 18" - 14", WOT redline is about 0.5" - 1".
Is it a N* 4.6 vin9? Does it matter?
Once I get a stable idle, I'll check again with the brake booster disconnected and then with it on. But with the booster connected, I don't ever see getting over 17" at idle as it sits now.

........ and, as always, atmospheric pressure (14.7 psi at sea level) pushes into a vacuum - the engine does not "suck in" air.
From one squid to another, this is always debatable. :cool2: Does the electron move to the positive post or the hole towards the negative???:hmm: Then again, we have the theory of relativity to consider.
AND let's not forget...the question of the refrigerator light...Does it really go out when you close the door?

Things that make you go Hmm...:hmm::hmm::hmm::bouncy::bouncy::bouncy:
Taz
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,286 Posts
Is it a N* 4.6 vin9? Does it matter?
Once I get a stable idle, I'll check again with the brake booster disconnected and then with it on. But with the booster connected, I don't ever see getting over 17" at idle as it sits now.


From one squid to another, this is always debatable. :cool2: Does the electron move to the positive post or the hole towards the negative???:hmm: Then again, we have the theory of relativity to consider.
AND let's not forget...the question of the refrigerator light...Does it really go out when you close the door?

Things that make you go Hmm...:hmm::hmm::hmm::bouncy::bouncy::bouncy:
Taz
-----------------------------
Once I get a stable idle,
I'll check again with the brake booster disconnected and then with it on.
But with the booster connected,
I don't ever see getting over 17" at idle as it sits now.

NO - and you won't until you get the misfire figures out -

why disconnect the brake booster?
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #15
-----------------------------
Once I get a stable idle,
I'll check again with the brake booster disconnected and then with it on.
But with the booster connected,
I don't ever see getting over 17" at idle as it sits now.

NO - and you won't until you get the misfire figures out -

why disconnect the brake booster?
Because the brake booster only held 17" max.
So my thinking is at 12" vacuum at idle, there is not enough for the fpr to operate correctly. So the engine stumbles a bit for lack of fuel and throws a misfire code.

When I get vacuum where it should be, I will test with and without the brake booster to see if it is affecting my idle.
Good game plan?
Taz
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,504 Posts
From one squid to another, this is always debatable.
Naturo abhorret a vacuo.

The 8th character of your car's VIN will be either a Y (275 hp, 3.11 final drive) or a 9 (300 hp, 3.71 final drive.)
ESC is a VIN Y, ETC is the 9.

----------

So my thinking is at 12" vacuum at idle, there is not enough for the fpr to operate correctly. So the engine stumbles a bit for lack of fuel and throws a misfire code.
In engine operation, as manifold vacuum drops, it's usually one result of increased throttle opening = increased power demand. The FPR goes richer at low vacuum signal. At idle the engine needs very little fuel/air to run, so the mixture is then very lean.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,792 Posts
So my thinking is at 12" vacuum at idle, there is not enough for the fpr to operate correctly. So the engine stumbles a bit for lack of fuel and throws a misfire code.
I think you have it backwards. The FPR is where excess fuel is routed back to the tank. As Sub said, fuel demand is lowest at idle (when vacuum is highest). The (intake manifold) vacuum pulls on the FPR diaphragm and opens the port to the return line. As vacuum decreases (when you open the throttle), the diaphragm closes and keeps higher fuel pressure at the injectors.


EDIT:
One of the pipes should be labeled fuel outlet with the arrow pointing in the opposite direction (to injectors)
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,504 Posts
Like this ? .............. and FWIW, the fuel pump always pumps far more fuel than the engine can use at any time - so the FPR also serves to port excess fuel back to the tank from that return nipple. (Of course, FPR fittings vary - ours drop into a receptacle - the diagram is a stand-alone unit.)
 

·
Registered
72,92,02 Eldorado
Joined
·
185 Posts
Discussion Starter #19
Naturo abhorret a vacuo.
Now I thought that only applied to between the ears.:D

I think you have it backwards.
I think you are correct. Thank you.

So now I'm really stumped on what the issue is. It runs great above 1000 RPM's. It will strumble and throw a P0300 code (no 301 etc) only every once in a while with no other codes or details, freeze frame. Maybe I'm testing the wrong software. I'm trying out TouchScan (PC) and Torque (on the pad).
Aslo, when the engine is up to temp and the top of the motor is still cool, it will not stumble. This morning it was 40F, ran to the store, idled for a bit. No problems.
Came home, it warmed up and it started stumbling.
I've replaced everything I can think of. Belts, filters, plugs, coil packs, fpr, egr. Plug boots look good (no tracking), have new ones coming in with the intake stuff. All vaccum lines look great and hold 20" for 5 minutes. No oil or coolant leaks.
I'm baffled.
Taz <---Please don't say ECM....
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,792 Posts
That's it Jim, thanks. Someday I'll learn how to do that.

Maybe you have a bad ICM causing the misfire?

Not enough vaccum at idle due to the plenum leak...Duh!
Go back and spray the plenum duct (the rubber coupler between the TB and the manifold) with Brakleen or such while flexing it with your finger. Concentrate on the bottom. If you get an RPM increase, that's your problem.
 
1 - 20 of 23 Posts
Top