'02 Impala: Diagnose This!

Colt Hero

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#1
Please fill out the following to ask a question.

MAKE:
MODEL:
YEAR:
MILES:
ENGINE:
DESCRIBE ISSUE....

Without first getting into a discussion of the problem, please review these three data captures and tell me if you see anything that would point to a problem. The Captures were taken on the drive home from work yesterday. 1st was coming out of work, heading toward highway. 2nd was ON the highway. 3rd was off the highway heading home.

Note: I *just* bought this OBD Scanner and I literally pulled it out of the box, plugged it in, and hit "Record Data", so while I *think* these Captures are legit, who knows??

BTW, the code is the familiar P0442, small EVAP leak. It had gone away for a few thousand miles after smearing a bit of Petroleum Jelly on the seal, but apparently it's back...

SnagitOfImpalaCentechDataCapture.png
 
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kev2

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#2
I would ask -
There was a DTC? guessing P0442?
System is in OL - open loop?
Why question mark at RPM capture 1?
1720rpm and 0MPH &
@2400 RPM and 28mph - snapshot taken at those conditions?
ECT 186 max, does it sometimes show higher?
academic but why did IAT decrease from ambient? I gotta think on that.

What did you smear petroleum jelly on - purge or vent solenoids - gas cap?
 

kev2

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#3
Can you see FTP (Fuel tank pressure) sensor voltages with scanner?
Freeze frame for p0442?
 

billr

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#4
MAF values look bogus, "stuck at about .06 #/sec. The 10* spark advance at 57 mph seems too low.
 

Colt Hero

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#5
Today's 3 Captures (notice I haven't cleared the P0442 DTC yet and the "MIL_DIST" continues to count up):

Once again, these are 3 contiguous Captures: Taking off from my driveway, then about 10 miles later taking off from a Red Light, then finally on the Interstate at about 70 mph, although the Capture doesn't seem to indicate that.

SnagitOfImpalaCentechDataCapture_2.png

kev2,

Yep - P0442. Sorry that wasn't completely clear. Kinda threw this post up quickly. And yeah, I smeared a thin film of Petroleum Jelly on the gas cap gasket. Made the code go away for quite a while. I guess I need a new cap since you cannot replace the gasket alone ...

OL = Open Loop. That's what I was thinking. Obviously not right. As you can see, today's 3 Captures all show "CL" for Closed Loop.

Question Mark on RPM Capture 1: Yeah - I don't know why. Haven't read the manual yet. It appeared at the far right on the display for that line item.

1720 rpm@0 mph & 2400 rpm@28 mph : That's what it showed. Like I said - just got this thing. Maybe I'm doing something wrong?

ECT <= 186 Deg F : That's it! Only three captures, so that's as hot as it got. I think the T-stat has been sticking on the open side because I haven't seen mid-scale in a while

No FTP (Fuel Tank Pressure) from what I can see, however - there *is* a PID for Fuel Rail Pressure, but I guess this tool either isn't reading it, or it's not being made available by this vehicle's PCM.
=====================
billr:

MAF could be a problem. Have seen MAP code @ 194k (Oct 2016), 190k (Feb 2016), 185k (June 2015), 176k (Dec 2013), 157,630 miles (Sept 2012). Ironically, these codes started after I had installed a new Denso upstream O2 sensor at 157,599 miles (Sept 2012), just 30 miles before the code first appeared !! I installed the new O2 sensor because at 157,251 (Sept 2012), I had a P0135 (O2 Sensor Heater Circuit Malf, Bank1 Sensor 1). Also had a P0401 at that time, so I cleaner the Throttle Body and the P0401 went away, but the P0135 returned, hence the new O2 sensor.

So maybe that Denso O2 sensor was never right to begin with??

================
As for this Scan Tool, seems to be kind of strange in that I can capture 3 sets of data - and it stores the 3 sets of data, but if I try to view this data back inside the house later on, it always tries to connect to the car first, fails, then when I try to view the 3 sets of data - it's the same data on all three Captures. But then if I go back to the car and connect it, I can see the 3 different sets of data. Strange.

Also - I guess I should run this thing on my 2011 Equinox to see if it shows the same set of data or different (or additional) data points. Not sure why it wouldn't show the Fuel Pressure. Seems like that would be available on every vehicle.
 
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kev2

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#6
The only thing we are working on is the DTC?

There is no fuel rail sensor on this vehicle.. so no data.

GTG
 

Colt Hero

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kev2:

No. Actually, the main problem is stalling at a stop. Car runs well enough back and forth to work when I take the Interstate, but if I come home through town, with several stop lights, at about the 18 mile mark (of 25 mile drive), stopping at a light can cause a stall. I can feel the downward spiral fairly quickly IF it's going to happen. An uneven, but faint rumbling idle which works itself into a stronger stumble, and then .... POOF ... stalls.

Also, on the Interstate - usually in the morning, I can feel engine misses *sometimes*, not always.

But *never* a MIL light (when the stumbling/stalling/misses are occurring) - except for this nagging EVAP code which hadn't shown up in a few thousand miles. Apparently I need a new cap.
 

billr

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#8
I'm wondering if the evap system is slowly pulling a vacuum on the fuel tank and starving the pump. You could try connecting gauge with long hose, so you could observe what fuel-pressure is doing as the engine dies/roughens. Or, try driving with the cap off (there is a little trap-door in the filler neck that would prevent fuel from sloshing out, right?)
 
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#9
Does putting a little pressure on the gas pedal prevent this engine stall? Sounds like a little problem we had with a 2002 Sunfire, pulled the IAC and hooked up to a variable 0-12V power supply, piston would not follow the voltage, gave it shot of choke and carb cleaner, was good to go again.

Another little problem was with the MAP sensor, it also tested good using a hand vacuum pump and ready the corresponding voltage. But its O-ring was dust, coated it with Permatex non-hardening gasket maker, was also good to good. It's this simple stuff.
 

kev2

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#10
An easy test - lets consider the TCC as cause of stall - shift to N at the stop where the stumbling starts - does it smooth out?

Bills thought about a vacuum drawing on tank - If we can see FTP sensor on scanner we would see the change, look into that sensor showing on your new scanner.
Try the Vaseline again that's a cheap test and think about a new cap.

Can you capture data when running good and be ready to capture as it spirals into stall?
ANd shifting to N - busy busy. JUst thinking out loud.
 
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billr

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#11
NickD, FYI: That Sunfire IAC is a stepper, it can't be moved with a 0-12V PS. You need to provide the proper step sequence to both coils.