(2006 Lacrosse 3.8) Warmish starts: car starts then dies, sometimes. Takes 3-4 tries. No CEL


#1

Hi.
I have a 2006 Buick Lacrosse with the 3800 Series 3 V6. It has 140K miles.
Lately on warmish starts (after shopping for example) the car will start then slowly die (not all the time but a good chunk of the time).
It starts fine when truly warm, and usually when it’s cold it’s fine too. It runs great otherwise. It never stalls or dies otherwise.
The car has new plugs and wires, a newish battery, a new air filter and I cleaned the MAF sensor. I’ve only had the car about 6 months, and noticed the problem in the last couple.
I scanned for codes and there are none, also there is no check engine light. The car doesn’t have an IAC valve or a fuel filter (I know those are common culprits)
But it starts easier when cold (even -20) than when warmish. Here are two videos I took of me starting it. *note the coolant temperature gauge. It’s partially warm.

Any help would be appreciated. Thank you. I am stumped!


#2

Clean the throttle body.


#3

I’d start first by verifying – when this problem is occurring – the battery voltage, the ecm’s engine coolant temp sensor, and the crank sensor for correct operation. If those test out ok, then , just my wild guess, you’re probably looking at a throttle body or fuel system problem. I’m presuming this didn’t start happening after you cleaned the MAF, right? i.e. You cleaned the MAF to see if it would help with the problem. But it didn’t.


#4

I would clean the throttle body as well. The next thing would be the MAF sensor…and finally…the AIC valve… Air Idle Control Valve…this part is responsible for the idle of the engine…and it is always fluctuating from being a high idle when cold…to a lower idle when warm and everywhere in between. If this part malfunctions…you will get symptoms similar. But try the easier items first…like the MAF which you did do…and definitely the Throttle body. Use a rag and some carb cleaner or TB cleaner spray…wet the rag and wipe where the butterfly valve closes…wipe the edges of the valve itself and the walls where it seats. Also look for any obstructed ports inside the TB… Your problem likely resides in these suggestions…ez enough to check into.

Blackbird


#5

@Honda Blackbird
OP tmanp said, " The car doesn’t have an IAC valve or a fuel filter (I know those are common culprits)"

That doesn’t sound right to me.
CSA


#6

The fuel filter is part of the pump assembly and non serviceable. The idle air control is all electronic (as the car is drive-by-wire). And, yes, I cleaned the MAF sensor trying to fix this. I’ve also unplugged the MAF sensor when it does this. It doesn’t matter. Thanks for the replies. I will look at the throttle body, though it doesn’t look dirty (when I was in there cleaning the MAF sensor and replacing the air filter). Do the videos help?? And the battery voltage is good. Thanks everybody!


#7

It does have an IAC system (a valve operated by a “motor” that’s driven by the ECU) and that should be removed and thoroughly cleaned as a first step.

Another thought that came to me was an engine temp sensor not producing an accurate resistance curve (not responding properly to the engine temp) causing the ECU to not properly meter the fuel when the engine is just warm.

These types of starting problems can be tough because ECUs don’t store fault codes during the starting sequence to send you down a particular path. If they did, every car on the road would trip codes with every start.


#8

Loss of residual fuel pressure? My hearing is pretty well shot due to a number of reasons so it was very difficult for me to pick things up in that video.

Guess I could mike it into my 300 Watt bass guitar amp… :wink:


#9

How can this not have an IAC valve ? Now I need to look it up… damnit

Blackbird


#10

IT SURELY DOES HAVE ONE

Blackbird


#11

Engines with electronic throttle control generally don’t have or require an idle air control motor.

This is the discription of the LaCrosse 3.8 L throttle body;

The throttle body functions similar to a conventional throttle body with the following exceptions:

•There is no longer an idle air control (IAC) motor and associated air passages.
•An electric motor opens and closes the throttle valve.
•The TAC module is located within the throttle body assembly.
•The throttle blade is spring loaded in both directions and the default position is slightly open.
•There are 2 individual TP sensors within the throttle body assembly.


#12

Strange…quite a few parts lookups do list one… Perhaps this vehicle falls outside the year ranges by a bit…but is incorrectly listed ? Seen that an awful lot of times.

Whenever I do a search for this part for this vehicle…I am greeted by the same picture of the part. Who knows…look up the part…and see if the engine has it. It could also be a Misnomer type of thing too. I dunno…parts lookups are confusing sometimes for sure.

Blackbird


#13

My daughter’s '04 Grand Prix 3.8 has the same throttle body, and no IAC valve. She also had some idle problems about 6 months ago. The TB looked clean at a glance, but was dirty behind the throttle plate. I cleaned it up and (so far) no more problems.


#14

Sounds right, we recommended this early on. The TB likes to be clean for sure.

Im still wondering why a lot of part lookups lists the item…and has a picture. Do a search for it…see what I am seeing out there…not the first or last time the lookup is askew.

Blackbird


#15

Okay, I’ll clean the throttle body. Any tips on that???


#16

Yeah…spray Carb or TB spray cleaner onto a rag…if you simply spray it… The sprays evaporate a bit too fast for my taste to have sufficient time to “work thru the crud”. The solvent action of the spray has more time to work when on a rag…and works pretty good with the friction of the rag and wiping it physically …instead of simply using the pressure of the spray itself…savvy? If the Butterfly valve in the TB is too deep or buried for you to physically touch it…then you are stuck simply using the pressure of the solvent from the can.

I always Spray/wet a rag with some Spray (Carb, TB spray, hell even brake cleaner and Starting fluid works)… reach into the throat of the TB and wipe it out… Open the butterfly valve and wipe its edges clean…wipe where the valve edge seats as well. Takes some fiddling to do thoroughly. You need something like wood or plastic to help hold the Butterfly valve open when you are trying to reach the Far side of the TB butterfly valve and its edges. Its kinda self explanatory really but the idea is to clean off the butterfly valve and where it seats in the TB itself and any small ports or holes in the wall of the TB itself.

In addition…since this is a Fly By wire…disconnect the battery when you do this. This will force the TB drive motor to go thru a “relearn” upon start up…which is good since you will have been reaching in there and man handling that valve…the removal of gunk can alter the Butterfly valve angle slightly…so a relearn is nice to do afterwards.

Respray that MAF as well while you are at it, it will most likely be disconnected at this time or not hard to get to anyways. If you see any holes or ports inside the TB make sure those are clean n clear…the red spray extender on the spray can is nice to use for this…it reaches in there nicely.

Dont forget to be using a RAG and spray to WIPE off these surfaces… Many people rely on the spray itself to do the cleaning of the TB…I find wiping it physically works best…after wiping it…you can then at the end, hit the entire area one last time with spray alone. Pretty simple…and often produces results.

I also suggest doing a Air Idle Valve lookup on some parts sites…look at the picture they show you, this is supposed to a picture of the AIC valve…It very well may be incorrect…but just see if you have the same part that comes up in that picture. Ive looked it up 3x and each time have been shown an AIC valve picture… Supposedly…you do NOT have an AIC valve. My thinking is that this is either incorrect…or the parts sites are wrong…or its a sort of Semantics issue with the naming convention of the part. Wont hurt to look it up…it takes a few seconds really… just see what I am talking about here.

Let us know…Good Luck

Blackbird


#17

Incidentally…if you listen to this weeks radio show… They talked about TB cleaning…Sometimes the guys used to give “Iffy” advice on the show I think its because they are trying to be entertaining in their responses. If often disagreed with Ray n Tom on their diagnosis’s on the show…but they were always entertaining. They usually get within the ballpark…but like here in the forum…or suggestions are only as good as the problem description.

People ask why they car is stalling out on them sometimes…and probe into all sorts of areas looking for a solution. They ask us on the forum…and often times leave things out. For instance…they wonder what could cause the car to stall so often…and FORGET to mention some significant noise, the raw fuel smell in the cabin, the leaking fuel tank or that the rear of the vehicle is completely Engulfed in flames…something like this. So again…only as accurate as the problem description. Hahaha

Blackbird


#18

I Had A Sticky Throttle Once Because Of A Coked Up Ridge In The TB Around The Throttle Plate.
The throttle plate was a reach. I found that spray TB Cleaner and a recycled tooth brush let me get back in there and scrub a little without scratching anything. I followed that up with solvent on rags to finish cleaning. It has never become sticky again after several years.
CSA


#19

I cleaned the throttle body (removed it and used a whole can of CRC throttle body cleaner. It was pretty dirty behind the throttle plate. This makes the car run better and the starting issue seems to be resolved! I really appreciate all the help from you guys! Now the car has new plugs, wires, cleaned throttle body and cleaned MAF sensor. It runs great now. Crazy what a difference a dirty throttle body makes! Thanks!


#20

Congrats on getting your ride back on the road with a smooth running engine!