GMC Safari

ont_galJune 21, 2010

Hi again..I havent had the need to come in here for quite awhile.

I own a 1995 GMC Safari AWD van

I very recently had the oil changed,tires replaced head lite taken care of...etc,little things

Now,on a trip out of town last week,it acted up

On the long drive,travelling on average @ 50 mph,it run fine...when I came to a small town or lights,it offered to stall.(this is VERY unusual for this vehicle)

At some places it actually did quit running and the engine light came on

It would start back up again with no trouble,and would idle in neutral or park,but I had to be quick with the feet to get it to run as far as actually travelling went.

I did put a container of the gas line anti freeze in it,thinking it might have been water in the fuel.(I am in Ontario and no,it isnt freezing temps right now)

A while later that day,I also put in premium fuel instead of the usual regular in the hopes that that too may help.

For the drive home,long distance,it again ran fine...but yesterday when I took it out again,when I had to slow down for the little towns and to turn into my driveway,again it offered to stall.

Is this enough info for someone to figure out what the problem might be?

Could it possibly be a dirty fuel filter?

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It could not be a dirty fuel filter. As the filter plugs up it causes problems when the engine is demanding more fuel such as accelerating, or cruising at higher speeds. Now that does not mean that it might not be due to be replaced, its just not the cause of the trouble.

Several things come to mind that can cause stalling at idle, but not affect driving at highway speeds. One is the torque converter clutch in the transmission. If the control solenoid for it is sticking then it could be trying to stay applied when you come to a stop. The sensation is similar to a manual trans-missioned car where you try to stop and forget to depress the clutch. Similar to your description they start right back up and will idle in park or neutral, but the moment you attempt to put it into drive or reverse, the transmission stalls the engine.

There are quite a number of other things that can cause the engine to stall when its hot, one is a sticking EGR valve, and problems with the throttle body getting coked up with carbon can do it to. When the check engine light came on was it because the engine stopped, or did it come on and then the engine stopped? If the latter, did someone pull the trouble code that was set?

    Bookmark   June 22, 2010 at 8:07AM
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When the check engine light came on was it because the engine stopped, or did it come on and then the engine stopped? If the latter, did someone pull the trouble code that was set?

The engine light came on first John....would stay on until the van stalled..when it was restarted,the light would go out for a bit,then come back on.
No one has had a look at it as yet,so,definitely nothing was pulled.
Could it be a sensor?
Now tonight when I took it out,I went about 3 miles or less,it stalled sure enough when I slowed it down to pull into driveway.
When it was shut off,I attempted to unlock the passenger door with the door panel electric lock and for the first time in that vans' history,it wouldnt work..could this mean that all of this is electrical?

    Bookmark   June 22, 2010 at 11:08PM
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It seems these problems began after a variety of maintenance work was down. Look under the hood for any misplaced items, for example, a small vaccuum line or electrical lead. While you are there, check the power center (fuses and relays) for blown fuses.

If you found nothing, then unplug the connector (on the bell housing or transmission) that controls the lockup clutch and take a test drive. The transmission should shift normally except the lockup feature will have been disabled. If the problem disappears, suspect a malfunctioning lockup feature. If there is no change, it is something else - reconnect the lockup connector.

    Bookmark   June 23, 2010 at 1:34AM
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ok,..will try that...but no,this just started in this van very recently..the maintenance was completed back in May..the van has been driven a fair bit since the work.

    Bookmark   June 23, 2010 at 4:21PM
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I took it into the local canadian tire and had it tested.They seem to believe it is more than likely a piece of carbon and broken off and gotten stuck in the EGR valve.

    Bookmark   June 25, 2010 at 5:44AM
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As part of the repair, did they re-program the computer with the newest software written by GM that corrects this problem?

    Bookmark   June 25, 2010 at 8:21AM
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As part of ther repair... What was the repair? Did they clean or replace the EGR valve?

If the EGR valve was held open, then your engine would stall as the throttle was returned to idle. With it stuck open, too much exhaust gas gets recirculate into the intake.

Cleaning or replacing the EGR valve fixes that problem.

Reprogramming the computer chip with the latest update probably does not affect a clogging EGR unless it promotes better combustion over the entire operating conditions.

    Bookmark   June 26, 2010 at 12:35AM
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Hi again...they didnt fix it yet as they seemed to think it "might" work itself thru-that is,this piece that may be in the valve

It goes in July !st to be cleaned and repaired

    Bookmark   June 27, 2010 at 5:27AM
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Just replacing the valve does not fix the car Jem. The problem is caused by chunks of carbon breaking off and being drawn into the valve when it is operating normally. One aftermarket solution was to create an EGR gasket that has a screen in it. This works to keep the valve clear, but eventually leads to a complete blockage of the passage between the exhaust and the valve.

The software update fixes the problem. The way the system was originally designed, they used the drivers (transistors) in the PCM to open the valve and spring pressure to close it. The reflash causes the computer to power the valve closed as well as open, plus increases the current to the motor, operating it with more torque which effectively crunches the carbon up and allows it to pass on through the valve.

You have seen me write about how cars have really been changing, and how shops and techs need to work harder and harder just to try and keep up with the changes in the technology, do you realize this is a 15 year old car, and the bulletin and the reprogram strategy to fix this came out about 12 years ago?

Imagine trying to multiply this by the dozens of things that could go wrong on any one system such as this EGR, times the number of totally different systems on a car, times the number of different cars (approx 280 models per year), times fifteen, the average life expectancy of today's cars. Is that a pretty big number for the possible repairs a technician could face any given day? That's why the number of times that even I can narrow down someones description of a problem here and give them an answer is so few. Even If I have seen something fifty times (and this one would be in that range) there is no way that I could reliably say for certain what the problem is this time. Now with the confirmation of the valve being held open, the fix must include doing the reflash to the newest software, otherwise the car's problem will return.

    Bookmark   June 27, 2010 at 11:18AM
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So,I should ask them then to do this "reflash" of the software then,should I

    Bookmark   June 28, 2010 at 6:06AM
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Yes, and here is the problem. The competitive pricing nature of the auto repair trade has seen many shops no make the investment in the tools, and the software to be able to provide that service. Yes, everyone thinks we are too expensive now and consumer experts have been telling everyone to call around for the cheapest price.

Consider how Newtons third law applies, "For every action there is an equal and opposite reaction".

It's quite likely that your first choice in a shop has tried to be too cheap and therefore they may first of all not even know about the re-flash (or else that's what they would have recommended) and they lack the tools and training required to do it now anyway.

Your going to need a top gun indy shop, or a dealer to have this performed. Some top indy techs actually provide this service for the other shops.

    Bookmark   June 28, 2010 at 9:08AM
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ok goes in on Thursday,and they do tell me that it is going to be re set AFTER its worked on..we'll see how it works and let you know afterwards--thank you

    Bookmark   June 29, 2010 at 3:49PM
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The re-flash is not a reset, as in to clear the codes that were set. Re-flashing means updating the actual software in the fuel injection computer to the newest level that GM has produced for your car. While the newer vehicles are done with pass through programming, yours may still be done by replacig the MEMCAL which has the programming stored inside of it. The bulletin number is 67-65-38.

    Bookmark   June 29, 2010 at 8:35PM
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thank u John...I will call the garage Monday and ask if they know what that is.

it was repaired on Thursday,the mechanic did say that it was carboned really bad(used to live in a small city where it didnt get much over 30km regularly)...anyways,they just cleaned it(EGR valve) to my knowledge and replaced the EGR gasket...its running smooth now,where when I managed to get it in there,it would hardly pull itself.
thank u again

    Bookmark   July 3, 2010 at 10:05PM
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What a way to drive! It's really annoying to have a car stalled in the middle of nowhere, it can be the fuel lines. It might be dirty and needs some cleaning agent to remove the clogs.

Here is a link that might be useful: GMC Accessories

    Bookmark   August 6, 2011 at 1:55AM
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