2004 Impala 3.8 stalling?

[dorlow]

This just started this morning. When coming up to lights, the rpm needle goes low then starts bouncing around then sometimes stalls. Any ideas what would be causing this? I'm guessing it's the fuel pump. Does anyone have any good diagnostics on how to test a fuel pump to be for sure that's the problem before I just change it out hoping it fixes it?

[maxwedge]

Normally the fuel pump would not act up like that, dirty throttle body and or dirty inop iac, stuck egr very common also.

[dorlow]

You just made me wonder if there's a vacuum line that came disconnected somewhere. I'll have to check around for that.

[dorlow]

Does anyone know if there vacuum lines in a 2004 impala? The symptoms I'm having are very similar to my 2006 Montana when a vacuum line was disconnected. I just looked in the engine compartment and don't see any in mine. Are there anywhere that I'm not seeing?

[dorlow]

So I just drove the car for the first time down the highway since the problem started. It has the problem going 70 mph down the road (which would make me believe rules out the iac seeing its cruising speed and not idling.) It will loose power for a few seconds and the rpm needle will die then suddenly have a surge of power and pull me back in my seat.

One thing I don't know if its related or not was on my 45 minute trip on the highway today, it only acted up for the first 15 minutes or so. But also while I was having the die and surge issue my cruise control didn't work. After I could tell the dying and surge went away, my cruise started working. Not sure if its a coincidence. Never had a problem with my cruise control in the last 8 years.

[maxwedge]

Die you mean loose power or cut out, the tech drops to zero as the engine fades or drops back some as the rpms drop?

[j cAT]

Originally Posted by dorlow

So I just drove the car for the first time down the highway since the problem started. It has the problem going 70 mph down the road (which would make me believe rules out the iac seeing its cruising speed and not idling.) It will loose power for a few seconds and the rpm needle will die then suddenly have a surge of power and pull me back in my seat.

One thing I don't know if its related or not was on my 45 minute trip on the highway today, it only acted up for the first 15 minutes or so. But also while I was having the die and surge issue my cruise control didn't work. After I could tell the dying and surge went away, my cruise started working. Not sure if its a coincidence. Never had a problem with my cruise control in the last 8 years.

could be fuel pressure,,, could also be water in the fuel. try 2 cans of dry gas and go to a different fuel depot.

[dorlow]

Originally Posted by maxwedge

Die you mean loose power or cut out, the tech drops to zero as the engine fades or drops back some as the rpms drop?

It's dropping down close to zero, but not sure if gets to zero. I just took my car into the body shop so I won't have it for a few days. (Reworking some work they should've done right the first time.) So, I won't know more until after I get it back. But people giving me suggestions is great. When I get it back, it will still be broke, so I'll have to start throwing some ideas at it.

[dorlow]

Originally Posted by j cAT

could be fuel pressure,,, could also be water in the fuel. try 2 cans of dry gas and go to a different fuel depot.

Always seems like when people have these symptoms, people always think bad gas. I've never seen it ever really be the case.

[dorlow]

So, I took my car to AutoZone. Even though the check engine light never came on, I asked AutoZone to run a scan on my car for my own piece of mind. The scantool showed my mass airflow sensor had faulted. I replaced it right in their parking lot with a new one and my car drove like a dream home. So, I've only drove it once sense, so I can't say for sure it's fixed, but pretty sure.

[Tech II]

Hope you have good luck....those aftermarket MAF's rear their ugly heads, too often.....

[dorlow]

Originally Posted by Tech II

Hope you have good luck....those aftermarket MAF's rear their ugly heads, too often.....

What are the symptoms of an aftermarket maf sensor bad? Is it the same as an oem one? Or do aftermarket ones have different symptoms they cause?

[dorlow]

Btw I drove my car again today without any symptoms so it appears its fixed.

[la1]

if someone has not mentioned it yet, check your intake manifold. They are notorious for getting leaks around the EGR . Even over tightening the bolts can cause the composit material to crack. Check your coolant for oil and your oil for coolant.