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Discussion Starter #1
Hello,

Don't get scared away by the length of this post.

Over the past few months I've been posting problems with my 2001 3.8L Impala. It seems I haven't been able to resolve any of them.

I'm ultimately trying to decide if I should fix this car by doing a major overhaul or just cut my loses and ditch it.

I would appreciate any feedback/solutions/advice as to what can be causing my problems, how to go about fixing them and whether or not it's worth it to keep investing in this piggy bank of a car.

My goal is to get the car to last until the spring.


Some background:
Car bottomed out in a ditch, did a 180. It seems all the problems stemmed from this incident, but maybe not.


Pre-existing problems:

Passlock
:: happens about once a month, sometimes more, sometimes less

ABS don't work
:: this is attributed to a faulty hub sensor, fixed it once, it reoccured, not fixing again


Problems after bottoming out in the ditch (developed over time):

Intermittent speaker outages
:: radio, chimes, cd player cut out from a split second to a few minutes once in a while

Frequent stalling
:: happens while in gear and while idling.

Radiator fan always on
:: coolant temp needle on dash stays at lowest point even when car is warm

Intake/Intake manifold
::eek:il collects on engine block, under intake manifold (small amount, but cause for concern). It seems like the dex-cool ate away at the gasket.
:: there's also a small gap between the intake manifold and the metal sensor housing/air intake to the right of the manifold.
:: one of the wires going into the mass air flow sensor was disconnected, reconnecting it did not solve stalling problem. Disconnecting the sensor during idle has no effect on engine rpm.


Here's some info I got by hooking up to the computer:

OBD codes:
PO128* - [Pending] Coolant thermostat (coolant temp below thermostat regulating temp)
PO172* - [Pending] System too rich
PO332 - Knock Sensor 2 Circuit Low

~codes associated with an O2 sensor and a sensor in the wheel hub (causes ABS, TC, not to work) came up when hooked up to mechanics code reader (mine didn't find these)

short term fuel trim: 0% to -1.5%
long term fuel trim: I've seen it between -8% and -17% :: @1500rpm -11% :: @idle (700-800rpm) -7.8%

after a drive:
intake air temp 12C
coolant temp 102C

@ idle
intake manifold pressure: 31kpa (is this high enough??)
air flow rate (MAF sensor) 4.2g/s


My observations/opinions:
From talking with mechanics there are a few possible culprits causing these problems:
ECU or PCM, intake manifold, MAF sensor, coolant temp sensor

We're talking a worst case scenario of thousands of dollars to fix unless I find cheap parts somewhere and do the labor myself.

The MAF sensor seems easy to replace. Same with the coolant temp sensor.
How hard/involved is it to change the intake manifold? Is there a guide/procedure anywhere?
Any advice on fixing the ECU or PCM if it came to that?

A big thank you for your help!!!
 

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Chances are your knock sensor code and lean code is due to a bad MAF sensor. The Upper Plenum is probably leaking, lower intakes barely leak on those engines. Get a dorman upper plenum, with a lifetime warranty. They're way better than OE. They're not too much if you're going to do it urself. If you get a MAF sensor I would get OE, but you can try a junkyard for that too. Also get a MAP sensor, they're relatively cheap, but I've had them when I replaced the Upper Plenum, the old map sensor doesn't hold causing a vaccum leak.
 

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Find a UIM/LMI from a L26 engine (05 GP GT, Buick Lucerne, etc...) Its alu, will hold up better than the plastic crap. Also replace the LIM/UIM gaskets w/ the (green) alum gakstes (avail from zzp/intense) The parts will run ~$200 and i can help you with the swap, but it's fairly straight forward. Should only take about 2hrs to do ;) You can get a used L26 intake from www.car-parts.com search for the 06 lucrene first. You MAY need a TB Adapter the Series III is drive by wire, the apaters are avail thru a few different 3800 vendors, i cant remember for sure though.

Passlock seems to be a pretty common issue w/ these cars for whatever reason, USUALLY a dealer only fix. Theres been a few threads in here about them (search passlock/security).

The stalling/SFTs/LFTs IMO would prob be MAF (possibly intake) related, i would start w/ the intake and rescan.. What software are you using to read them?

Hub bearing/TC issues, if you get a cheap replacement hub, you'll end up replacing it every year or two, I've had a Timken for about 2 years now w/o issue...
 

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In addition to the above suggestions I would also change both O2 sensors. If one or both are not reading correctly that will keep the PCM in its startup/cold cycle tring to give the engine more fuel.

The PCM temp sensor can also cause the rich fuel condition. It is not the same sensor as the dash gage unit.

I doubt your PCM is giving any issues.

Over all this car can be fixed for not a whole lot of money.
 

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Discussion Starter #6
Will fix. Ordered parts.

Thanks for all of your responses!

I have decided that I am not going to bother fixing the hub, passlock or radio problems.

However, I did order the Dorman intake manifold for $172CDN (PN 615-180 for anyone interested) like capricewiz suggested. It's a direct replacement and it comes with the gaskets. I'll have it tomorrow.

I also ordered a new MAF sensor. The GM dealership had one for $560CDN so I got an aftermarket one for for $233CDN.

I'll start by replacing the UIM and MAF sensor and I'll see where that gets me.

04detroitls:
I'm sure the l26 alum manifold is better than the one on my car but I don't want to play around with any TB mod plates. I did find the UIM and LIM from a 2005 grand prix for 250CDN but I would need gaskets on top of that so we're talking about 300 bucks or more. If anyone is interested in a L36 composite upper intake manifold (UIM) to L26 aluminum upper intake manifold conversion, this is a good start: http://www.automotiveforums.com/t701174-l36_composite_upper_intake_manifold_swap_to_l26_aluminum_uim.html

04detroitLS:
Would you mind getting me through this manifold replacement? If it's not too cold outside, I'll do it myself. A few questions right off the bat: Do I need to drain any liquids? Are there any special tools I need?

77impala:
I had the O2 sensor problem before the stalling started and the fuel trims were between 0% to -5% at the time. It's quite possible that what you're saying is true but I'll wait till I install the new manifold and MAF sensor before going any further.

George Bate Auto:
I agree with you but...
The MAF sensor and manifold are running me 400CDN right now. I'm confident I can replace both myself. If this fixes the problem, I'll be happy. Like I said, I don't want to buy a new car during the winter so I need this one to last me till the spring or early summer. 400 is less than one monthly payment on a new car. If I hold off on a new car for 6 months until the house is paid off, I'll be able to save over 400 bucks on interest by paying off the new car faster.

Thanks again for all your help!! I'll post back with an update.
04detroitLS, your help with the manifold would be greatly appreciated! :)
 

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Discussion Starter #7
OBD code reader software

04detroitLS:
I forgot to mention my code reader info.
I'm using an ELM327 code reader.
Right now I have the 1.13 Scantool.net software but I'm looking for something better.
 

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If you're just doing the upper plenum, you don't need to drain any fluid.
You'll need, a small flat head screw driver. 2 Regular flat head screw drivers. An 8mm deep and shallow, a 10 mm deep and shallow, A 3/8inch socket. I prefer all 1/4 in drive. And a 4inch long 1/4 drive extension and a ratchet. Also a small pick. A can of brake clean and a rag. A set of plyers because you'll have to take the EGR tube out of the lower intake for that dorman kit, since it has a fix for the common problems of the UIMs. I would also keep a bit of some kind of grease with you to help the injectors slide in place.
 

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Discussion Starter #14
If you're just doing the upper plenum, you don't need to drain any fluid.
You'll need, a small flat head screw driver. 2 Regular flat head screw drivers. An 8mm deep and shallow, a 10 mm deep and shallow, A 3/8inch socket. I prefer all 1/4 in drive. And a 4inch long 1/4 drive extension and a ratchet. Also a small pick. A can of brake clean and a rag. A set of plyers because you'll have to take the EGR tube out of the lower intake for that dorman kit, since it has a fix for the common problems of the UIMs. I would also keep a bit of some kind of grease with you to help the injectors slide in place.
Thanks for the detailed list capricewiz; it looks like I'm set. I thought I might need something special like a GM fuel line disconnect tool or something like that.
I'll do the plenum swap on the weekend and the MAF sensor tomorrow.

Cheers!
 

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Discussion Starter #16
New MAF sensor: no change.

Alright, so replacing the MAF sensor didn't do anything.

I found extensive info on how to replace the upper manifold plenum at repairprocedures.com.
You can get 24hr access to any repair procedures for free (comes with pictures). Unfortunately, my garage holds everything but my car, so I'd have to do this on the driveway. It's a bit chilly here so I'm gonna get a quote from my mechanic to see how much he wants just for the labor then I'll decide if it's worth freezing my butt off.

I have a question: If the second 02 sensor isn't tracking the first one, could it mean that my cat may need to be replaced? I know that a clogged cat will kill the performance of the car but can it cause sporadic stalling?
 

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A bad cat can make the car stall, i have been in cars where the cat is so bad you can floor the car and it barely moves and after it moves a bit it dies.
 
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