Car

Ask a Mechanic Online and Get Answers to Your Car Questions

Ask an Expert,
Get an Answer ASAP!

Car

1999 pontiac Grand Am SE: sedan..equipped..2.4L I4, 4 spd auto trans

Customer Question
ok, got a problem child.....
ok, got a problem child... 1999 pontiac Grand Am SE 4 dr sedan, equipped with 2.4L I4, 4 spd auto trans... Veh is also equipped with a mandatory immobilizer device.

Veh no start... assumed was run out of fuel as the fuel gauge was not working, filled tank with premium unleaded gasoline and towed to a garage.

what''s been done: (DTC P0300 set)

1) Fuel flow test: failed - replaced fuel pump (also corrected the malfunctioning fuel gauge as it is an intergral unit), retested - fuel flow at proper levels. Fuel filter replaced with new pump.

2) Fuel pressure test: failed - replaced fuel pressure regulator. retested - fuel pressure at 58 psi (prime pulse) and 45 psi at engine idle. fuel rail and injectors inspected for dirt and deposits, cleaned then reinstalled. Injector pulse test confirmed injectors working properly with no leaking/dribbling.

NB: engine runs like a bag of hammers at anything above idle, then stalls.

3) Sensor + actuator tests: IAC motor removed, inspected, cleaned and re-installed - ok, Map sensor vaccum tested, voltage readings confirmed with both scan tool and Voltmeter - ok. TPS voltage and resistance test, confirmed with both scan tool and volt/ohm meter - ok.

4) Ignition system tests: engine crossover/misfire on cyls 1 + 4. Further testing concludes ign coils - ok, ign module - ok, ign coil housing, plug boots, and contact springs - ok.

NB: engine runs fine at idle, acceleration off idle, results in misfire condition, sag, hesitation and stumble, resulting in stalling.

NB: engine restarts after stall.

Summary: Spark, ignition timing, engine mechanical, all within mfr specs. Engine runs perfectly at idle. Transmission has no DTC set. engine continues to set DTC P0300. (confirmed with CRT Oscilliscope on cyl''s 1 + 4)

Conclusion: Catalytic Converter? From discussions with other mechanics, an immobilizer installed thru the primary ignition circuit may result in momentary power loss (less than 1 millisecond) where the vehicle computer detects a misfire and compensates with an increased injector pulse width. Over an extended period, this can possibly cause the premature failure/clogging of the catalytic converter, resulting in the condition presently being experienced.

NB: this conclusion has yet to be confirmed with an exhaust system back pressure test.

Comments from other Master Techs are appreciated.
Submitted: 9 years ago.Category: Car
Show More
Show Less
Ask Your Own Car Question
Answered in 1 hour by:
3/1/2008
Auto Mechanic: Mazda Ed, Auto Service Technician replied 9 years ago
Mazda Ed
Mazda Ed, Auto Service Technician
Category: Car
Satisfied Customers: 2,223
Experience: ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience!
Verified

HiCustomer

First let me say that it sounds like you have a high skill level and none of my comments are meant to offend.

That being said, how did you test the ignition coil housing. It is impossible to test using resistance tests or any other method besides swapping a good one in it's place. I find that most often these fail internally where you can not see it. The spark arcs through the closely spaced firing tubes at the bottom of the housing.

Also, I recommend swapping the position of the 2 coils to see if that changes the cylinders misfiring. We have several of these cars come into the shop with a misfire condition. Typically the customer has replaced many of the sensors/components EXCEPT that coil housing.

Also, if you are suspecting the aftermarket device as the source... Can you monitor the ignition voltage with your scope to look for a dropout? Can you temporarily bypass the device. I have done this before on the state installed DUI boxes to test the vehicle control system.

Ask Your Own Car Question
Auto Mechanic: Mazda Ed, Auto Service Technician replied 9 years ago

HiCustomer (attempt #2)

First let me say that it sounds like you have a high skill level and none of my comments are meant to offend.

That being said, how did you test the ignition coil housing. It is impossible to test using resistance tests or any other method besides swapping a good one in it's place. I find that most often these fail internally where you can not see it. The spark arcs through the closely spaced firing tubes at the bottom of the housing.

Also, I recommend swapping the position of the 2 coils to see if that changes the cylinders misfiring. We have several of these cars come into the shop with a misfire condition. Typically the customer has replaced many of the sensors/components EXCEPT that coil housing.

Also, if you are suspecting the aftermarket device as the source... Can you monitor the ignition voltage with your scope to look for a dropout? Can you temporarily bypass the device. I have done this before on the state installed DUI boxes to test the vehicle control system.

Ask Your Own Car Question
Customer reply replied 9 years ago
Reply to Mazda Ed's Post:

Hey Ed:

The ignition system has been fully tested, including hooking up an old CRT osilliscope to watch for any peaks/drops caused by internal shorts. The coils have been swapped, and no change found...

Once again, the engine runs perfect at idle, but drops off immediately at any speed above idle. (misses, surges, then stalls). WOT results in immediate stalling of the engine. DTC P0300 is the only code being set.

?Plugged catalytic converter???

Drop me a message back thru PM.
Cheers, Jay

Customer reply replied 9 years ago

Attention: all automotive experts.

FYI - My problem child, a 1999 Pontiac Grand Am SE (2.4 L with 4 spd auto trans).
The problem/fault has been solved... The culprit is a plugged Catalytic Converter causing excessive back pressure resulting in the engine's exhaust gases not being properly vented from the cylinders, which in turn is causing the HO2 sensors to have false readings of a 'lean condition'. Overall this fault is causing the ECM to over fuel the engine.

How was it found?

After exhausting all the diagnostic procedures associated with the DTC P0300 to be set, which included the entire fuel system, and ignition system. I removed the Catalytic Converter from the vehicle and...

Low and behold, the engine responded with a roar! (I remembered to wear my hearing protection, but it was loud enough to be heard in the shop office.)

2.4 Hrs later, the vehicle was fitted with a generic replacement catalytic converter, that had to be welded into place, and the absolutely joyful customer was merrily settling his invoice and headed towards a vacancy withing a stream of traffic.

This particular fault had 2journeyman mechanics stumped for a week... I received the vehicle from them and spent a total of just over 20 hrs in diagnostics.

Something to watch for in the future,

Cheers, Jay

 

Auto Mechanic: Mazda Ed, Auto Service Technician replied 9 years ago

Now you need to find out WHY the convertor went bad! Typically it is an outside influence such as a misfiring cylinder or skewed oxygen sensor, possibly even excessive oil consumption. I can't recall finding a bad convertor without an actual cause.

Ask Your Own Car Question
Customer reply replied 9 years ago

After consulting with the customer, the vehicle was driven repeated short distances without the engine reaching full operating temp... The suggestion was made to the customer to give the car a good long run of both city and highway driving. He returned with the vehicle later in the day, and reported he was very pleased with the way the car was handling and running. He also noted the exhaust system vented a lot of carbon...

Cheers, Jay

Customer reply replied 9 years ago

FYL: Further to the problem child... After checking the vehicle history file from the immobilzer installer company, this vehicle has been recalled by them to have the immobilizer installation modified.

The Immobilizer installer used the primary ignition circuit, which for all GM products is a 'No - No"... They are correcting the wiring for the immobilzer to the secondary ignition circuit to correct a known drivability fault. This Vehicle is also being sent to the local GM dealer to have it's ECM chip reprogramed with information that includes the immobilizer functions.

Information for everyone to file away for future reference.

Cheers, Jay

Ask Mazda Ed Your Own Question
Mazda Ed
Mazda Ed
Mazda Ed, Auto Service Technician
Category: Car
Satisfied Customers: 2,223
2,223 Satisfied Customers
Experience: ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience!

Mazda Ed is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry.

Stephanie PElm City, NC

used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future.

David L.Richmond, TX

9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much.

PhilMarysville, CA

Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible.

CharlesWalnut Creek, CA

As a single woman, I really appreciate an excellent and affordable opinion.
Thank you Geordie, I will not hesitate to contact justanswer in the future!

SueCharleston, WV

Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff.

JimCastleberry, FL

The nearest Volvo dealer is 160 miles away. Best $15 bucks I have spent in a long time!

Paul MCorpus Christi, TX

< Previous | Next >

Meet the Experts:

Chris (aka-Moose)

Chris (aka-Moose)

Technician

1,243 satisfied customers

16 years of experience

Ted G.

Ted G.

ASE Certified Technician

1,724 satisfied customers

20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness

George H.

George H.

ASE Certified Technician

1,537 satisfied customers

ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist

GM Tech (Cam)

GM Tech (Cam)

Auto Service Tech

669 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Amedee

Amedee

Former ASE Master Tech

2,520 satisfied customers

ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector

Jerry

Jerry

Master Mechanic

2,181 satisfied customers

ASE master, 30+ years. All makes and models. Trouble shooter, shop forman, service manager

Richard

Richard

ASE Certified Technician

1,000 satisfied customers

12 years Ford Lincoln/Mercury Jaguar dealership as a technician and shop foreman reparing all makes

< Previous | Next >

Related Car Questions
I have a 2002 Toyota Solara. I just noticed that one of my
I have a 2002 Toyota Solara. I just noticed that one of my headlights is out. What should it cost at a shop to replace the bulb?… read more
baddad1
baddad1
technician
High School or GED
5 satisfied customers
Losing power checked with code reader P0113 intake temp
losing power checked with code reader P0113 intake temp sensor … read more
Cesar Jimenez
Cesar Jimenez
Owner/CEO
Vocational, Technical or Trade School
110 satisfied customers
Audi Q5 front brakes worn down after only 11,000 miles.
Audi Q5 front brakes worn down after only 11,000 miles. Sounds strange to me. … read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
My 2010 odyssey sliding door on the driver side will open
My 2010 odyssey sliding door on the driver side will open some times but not always . Then after a few days will start working again … read more
Pete
Pete
Independent Auto Technician
Vocational, Technical or Trade Scho
138 satisfied customers
Cant get back sliding door open passenger. just makes noise
Cant get back sliding door open passenger. just makes noise but will not open. … read more
Dan
Dan
Dealership Technician
Associate Degree
1,786 satisfied customers
I need to talk personally to a mechanic about my situation
I need to talk personally to a mechanic about my situation they would be a lot of typing and it would be much agers just to call the technician … read more
kalamykid
kalamykid
Pactor automotive
Vocational, Technical or Trade Scho
97 satisfied customers
I just bought a 1995 Damon Ultrasport. There are three
I just bought a 1995 Damon Ultrasport. There are three switches on the steps going into the RV. Two are white and one is red. What do they go to? … read more
Randall
Randall
Auto Technician / Consultant
Vocational, Technical or Trade Scho
69 satisfied customers
Code po344 in a 2012 Chrysler 300 3.6. Camshaft sensor. I
code po344 in a 2012 Chrysler 300 3.6 JA: Just to clarify, what's the exact code? And have you tried to reset it? Customer: camshaft sensor JA: Are you fixing your 300 yourself? What have you tried so… read more
Curtis
Curtis
Vocational, Technical or Trade Scho
1,694 satisfied customers
The car wont turn over the batt is up I make the starter
the car wont turn over the batt is up I make the starter crank by crossin the stater solenoid where to look? … read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,429 satisfied customers
2000 Toyota Sienna 3.0 Had multiple cylinder misfire 1-6 as
2000 Toyota Sienna 3.0 Had multiple cylinder misfire 1-6 as well as lean bank one..... Changed Plugs,Wires, and engine air filter... Cleared codes and lean bank one is still coming back. Vehicle has n… read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,429 satisfied customers
We set the timing according to the diagram. Once it was all
Eric, We set the timing according to the diagram. Once it was all together, we started the vehicle and cylinder 4 and 5 were misfiring with no cam crank corillation codes, just misfire. We pulled the … read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
I have a 2007 Hyundai Sonata NF Elite and it's done 117000
I have a 2007 Hyundai Sonata NF Elite and it's done 117000 kms. I've just been asked if the timing belt has been replaced as I"m trying to sell it but it doesn't appear so. Was it due at 90000? … read more
George H.
George H.
ASE Certified Technician
Associate Degree
1,537 satisfied customers
Have an 04 Navigator 4WD crank no start, suspect FPDM but
Hey, have an 04 Navigator 4WD crank no start, suspect FPDM but have looked under rear can not find it, where is it located. … read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,429 satisfied customers
Got a new battery and alternator but car still wants to die
got a new battery and alternator but car still wants to die when it comes to a stop. When i am driving and giving it gas it seems to be fine. … read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
What is the inner diameter of the power steering return hose
What is the inner diameter of the power steering return hose for a 1999 buick park avenue Ultra… read more
Edward Clayton
Edward Clayton
Associate Degree
1,033 satisfied customers
Online really or BOT. Pathfiner 2006. Is this human or BOT?
Heater wont blow hot to driver side, but blows to passenger side … read more
baddad1
baddad1
technician
High School or GED
5 satisfied customers
Front brakes are sticking, I have replaced the calipers,
Front brakes are sticking, I have replaced the calipers, rotors, pads and still sticking. Could this be the ABS/HCU unit? … read more
Expert
Expert
16 satisfied customers
The car starter turns over but is not cranking the engine,
Hi, the car starter turns over but is not cranking the engine, put in a new battery but no change. seems like the starter solenoid may not be engaging. … read more
Gary
Gary
Senior Technician
Vocational, Technical or Trade School
61 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x