Question about 2001 Pontiac Montana

2 Answers

Veh. starts and runs perfect for a minute or two then stops and will not start for about an hour or two. Appears it is not getting any gas. Had two people work on the veh. (one Pon.) one replaced the cam censor the other cleaned the air censor. Neither helped!

Posted by on

Ad

2 Answers

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Master
  • 1,606 Answers

A shotgun parts changing approach will waste a lot of time and money. This calls for using instrumentation to try to catch the failure.

1. You say it appears it is not getting any gas. Can you attach a fuel pressure sensor to the system? I don't know about this vehicle, but many fuel injection systems have a Schrader valve for a pressure gauge or relieving fuel pressure for service. If the pressure builds rapidly when you start the engine, then falls until the engine quits, you may have a clogged fuel filter or other obstruction in the system. If it holds steady for while, then rapidly drops just about the time the engine quits, something is telling the engine computer to turn off the fuel pump (a safety feature).

Check for normal exhaust flow out of the tailpipe, and take a gentle sniff for abnormal odor (strong gasoline odor, smoky, or otherwise dirty exhaust). Your nose is a good instrument for detecting abnormal combustion. Low flow indicates an obstruction such as a foreign object in the tailpipe or melted or clogged catalytic converter. Flow with interruptions indicates misfiring.

2. What does the engine computer readout say? Sometimes it will tell you directly, for example, a bad connection in the ignition module that opens when it gets warm will probably set a code identifying a failed ignition module. On the other hand, sensor errors can have multiple causes. Try to get the values measured by the various sensors and compare them with normal parameters. This will help to make sense of the fault code(s). You'll need an ODB II diagnostic readout tool to get this info. Some car parts stores will provide the use of one for free or a nominal rental in hopes of selling you repair parts.

"A minute or two" is just about long enough for the engine to start "closed loop" operation, when the oxygen sensors are warm enough to send mixture adjustment information to the engine computer. You can check that out by blowing cold air on the oxygen sensors after the engine stalls to see if that significantly reduces the time before the vehicle will restart. If that works, you'll know a look at the airflow sensor was not a bad guess. Focus on that, the oxygen sensor and the throttle position sensor readings first.

3. If you haven't identified the problem by this point, measurements with basic instruments (voltmeter, oscilloscope) are next. The engine computer supplies one or more regulated voltages to power some of the sensors. Make sure these are within tolerance.

Very few manuals refer to the use of an oscilloscope because it's an expensive instrument, and some knowledge is required to interpret the display, but, properly used it is one of the most efficient tools there is for checking electronic sensors and fuel injector problems. If you can get an oscilloscope probe into the engine computer connector (you can slide a short piece of 24 AWG bare solid wire into the wire pocket and hook a 'scope probe to that), you can view the waveforms for the fuel injector drive and ignition pulses, and check for sensors opening up (voltage suddenly goes to zero or maximum voltage) or having very noisy output or other anomalies. Don't forget to verify the ignition switch connection while you're looking at the computer connectors (assuming the previous oxygen sensor cool-down had no effect).

I recommend measuring at the computer even though it access is awkward because the wiring harness in the engine compartment is made to be sealed against a harsh environment, and it is difficult and awkward to probe there without either making temporary adapter connectors or damaging the wires by poking holes in the insulation (a bad practice used by some shade tree mechanics). Professional technicians often use a "breakout box", which is inserted between the firewall connectors and the engine wiring harness. This provides convenient exposed points for electrical measurements.

I wish I could give you a specific answer, but this is the reality of modern engine service. Many of the traditional tests are still useful, but sometimes you have to get into combustion chemistry and electronic diagnosis.

Posted on Nov 03, 2010

Ad
  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Master
  • 398 Answers

Is the check engine light on? Seems like it need a tune up or bad fuel pump, If you have a little mechNIC SKILLS .. You can try this to let you know if its fuel related or electrical.. Get some staring fluid. Start the car and after it dies and wont start. Spray the starting fluid in the breather or throttle body for 3 seconds. If it starts it will be an electrical problem...Good Luck!!!

Posted on Nov 03, 2010

Ad

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

I stopped and got gas this morning. About 20 minutes later the car started losing power and shaking. We put a computer on it that says it was a P0300 Multiple Cylinder Misfire detected! By the time we got...


It could have been water in the gas or bad gas, either way i would run some dry gas threw it and i wouldn't get gas at that gas station for a while.

Aug 24, 2013 | 2002 Oldsmobile Alero

1 Answer

2000 buick la sabre was working very well. it sat


try dumping some gas line antifreeze into the tank

Jul 28, 2010 | 2000 Buick LeSabre

1 Answer

1991 ford escort gt car will not start car was running stalled on dash fuel cut off appeared


Possible inertia switch if veh is equipped, let me get this right though, the light came on when the veh stalled??? didnt they all come on???? warning lights i mean???? try pouring a lil gas into the throttle body and then turning over with the starter, if this works and makes it run for a second then your veh is not getting fuel. if its not getting fuel, then there is no fuel pressure. If there is no fuel pressure there is either a leak that you would almost have to see, or the fuel pump is not running. One way to tell if the pump is not running is to have someone turn the key to the run position while you kneel at one of the rear tires of the veh. you should hear the pump come on for 1- 3 seconds, kind of a whining sound, but slight. If its coming on, but the veh still wont start without adding fuel ,that still doesnt mean that the pump is good, but will eliminate the inertia switch. reply and we go from there...

Oct 13, 2009 | 1991 Ford Escort

1 Answer

Won't re-start after stopping for gas/rest during road trip.


This problem sounds like you have a fuel pump over heating and shuts of the relay. When it cools off the relay kicks in and you can restart your vehicle. Replace your fuel pump and the problem will go away.

May 26, 2009 | 2000 Isuzu Rodeo

1 Answer

04 Titan Does not stay on when cranked


if veh have malfuntion ligth on may be is the cranck possition sensor or the cam sensor, olso if there is no codes
is the IPDM ir intelylled power distribution module veh will cut off when running

Mar 10, 2009 | 2005 Nissan Titan

1 Answer

2000 alero, started up fine, after about 5 mins on road upon accel it hesitated and felt as if it would turn off. Came to a stop and then upon accel to go., same thing. Went down a hill and upon accel to...


This is a Direct result of a Bad Alternator. You can Run on what is left in the Battery for a Little while and if it sits for a While the Battery will retain enough Power to Start. You may need a New Battery in Addition.

Jan 17, 2009 | 2004 Oldsmobile Alero

Not finding what you are looking for?
2001 Pontiac Montana Logo

293 people viewed this question

Ask a Question

Usually answered in minutes!

Top Pontiac Experts

Marvin
Marvin

Level 3 Expert

81400 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22359 Answers

Jeffrey Turcotte
Jeffrey Turcotte

Level 3 Expert

8841 Answers

Are you a Pontiac Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...