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Old 07-25-2011, 11:51 AM   #1
peterdemski
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Default '99 Malibu 4cyl hard start/hesitation/miss

First off Hello Malibu forum! I recently signed up in hopes that I'll be able to solve a very long standing issue with my G/F's car. so first off I'll try and list off all the symptoms I can remember:

1. Car starts hard. You have to pump the gas pedal to get it running typically. There is also a rich/unburnt fuel smell normally when it starts since the exhaust leaks it's easy to notice. It seems to start better when cold than hot.

2. The car will miss slightly when sitting at idle. this seems intermittent but worse in hot weather.

3. The car will miss/chug when accelerating from idle(stopped). This can be improved by accelerating slowly.

4. The car will miss/chug on the highway in Overdrive if you give it enough gas to put a load on the motor but not have it downshift. The engine smooths out when it downshifts and the RPM's get up. This ALWAYS occurs.

5. The car will stall out on very very hot days when travelling slowly(stopped at a light). *G/F has had this happen a couple times however even in the 100F weather we've had in Michigan lately I haven't had this problem.

6. Engine light on. 2 codes stored. 1: Exhaust leak(leaking from flex joint on back of manifold). 2: fuel vent to atmosphere leak.


The G/F has had it to at least a 1/2 a dozen shops over the last few years trying to get it fixed and so far no shop has been able to figure it out yet.

Repairs I know of:
Fuel Pump/Fuel Filter - Replaced again last week under warranty on defective pump
EGR Valve - 6-12 months ago?
Fuel Pressure Regulator - ? G/F says it was replaced but that would have been >2 years ago.




I've been driving this car for the last few months after a brake line failed as it's not been very reliable and she's not very good at babying the car to minimize the current issues. I'm not all the familiar with these cars but I can turn a wrench just fine once I know what the problem is however I need a starting point to diagnose the issue. From the symptoms does anyone have a hunch on what it could be?

Thanks in advance!

Peter
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Old 07-25-2011, 11:59 AM   #2
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Of course, the standard routine maintenance items should be checked / done:

Spark plugs
Spark plug wires
Air filter
Clean MAF sensor
Check for vacuum leaks.
Check your gas cap.
Fix the exhaust.

These are ALL routine maintenance items that will affect how your car runs. Before I worried about ANYTHING else, I'd check all of those.

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Old 07-25-2011, 12:17 PM   #3
peterdemski
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Sorry I had forgotten that. A tune-up was performed on the car about a year ago which included new plugs/wires/air filter/PCV Valve. I believe that the gas cap was also replaced around that time. I've done a cursory check of vacuum lines however I haven't done a leak check. To my knowledge the MAF hasn't ever been cleaned so I will start with that and go over the vacuum lines.

As for the exhaust leak is it possible to replace just the can shaped flex joint at the back of the manifold? Is it just a compression fit or is there something that's supposed to be holding them together(that would obviously be broke in my case)? The shop my G/F took it to last quoted her a couple hundred bucks to fix it as they were going to replace the cat to the manifold.

Last edited by peterdemski; 07-25-2011 at 12:31 PM.
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Old 07-25-2011, 01:35 PM   #4
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Stalling out under load or from a stop (also a large, sudden load) suggests to me that you have an air leak after the MAF (PCV maybe?) or a vacuum leak.

Maybe pull the hose going to the brake booster to see if it has fluid in it. If it does, that's a repair right there.

Check for obvious signs (which it sounds like you've done), but also check the work performed by others. They may have left something off, loose, or misaligned, either by accident or through neglect or incompetence. But that's just pointing a finger. We're more interested in helping you solve it.

A test you could try is to have your GF put it in D, set the parking brake, hold the foot brake securely, and hit the gas. As it starts to stall out spray water or WD-40 around the throttle body and intake. If you hear the noise change you may have just found your issue.
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Old 07-25-2011, 02:57 PM   #5
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Quote:
Originally Posted by RalphP View Post
These are ALL routine maintenance items that will affect how your car runs. Before I worried about ANYTHING else, I'd check all of those.
AND fix the things that are known bad......by the trouble codes.
Especially that exhaust leak as that can be DEADLY under some circumstances.
How many other recommended "fixes" has she rejected because of cost ??
You/she might be your own worst enemy here.

Many of the things you described sound like a spark "leak", commonly from the spark jumping across a boot to ground but it can be plugs or wires too.

P.S. On a fuel injected vehicle, "pumping" the gas really does NOTHING.
Holding the pedal down just a little bit might help under some circumstances.

P.P.S. How many miles ? It's 12 years old now. At some point you need to consider trading it in.

Last edited by MalibuKen; 07-25-2011 at 03:02 PM.
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Old 07-26-2011, 07:29 AM   #6
peterdemski
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Thank you very much for the suggestions. I'm planning on cleaning the MAF tonight and taking a closer look at the vacuum lines to see if anything is weathered looking. It looks like the new exhaust piece wont be too bad to replace so I'll be ordering that in the next couple days. I'm about 6 weeks post shoulder surgery so I've got a 5lb weight restriction on one arm so it may be a couple weeks before that gets installed unless the G/F is willing to help me out which I'm sure she will.

I will also see if I can find any air leaks around the TB/Intake area to see if I can find a leaking gasket.

Also I asked my G/F about the gas cap and although a year or two ago she insisted it had been replaced she now said she couldn't remember so I'll be picking up a new on and checking to see if that takes care of the vent to atmosphere code.

Quote:
P.S. On a fuel injected vehicle, "pumping" the gas really does NOTHING.
Holding the pedal down just a little bit might help under some circumstances.
Yes I am aware of this however the car won't start most of the time without pumping or holding the pedal open at least a little so even if it's just providing less air restriction by opening the butterfly in the TB it's making just enough difference to let the car start.


Quote:
P.P.S. How many miles ? It's 12 years old now. At some point you need to consider trading it in.
the car has 160K miles on it.


Well wish me luck! Hopefully I'll have at least some new information for you guys in the next day or two and some new parts on the way.

Thanks again for all the help!

Peter
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Old 07-26-2011, 08:02 AM   #7
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Quote:
Originally Posted by peterdemski View Post
the car has 160K miles on it.
Time for a little soap box.

IF you plan to keep a car a LONG time, you really NEED to fix the "little" things as they come up .........so they won't add up to a big mess later on.

I'm afraid that you might be at the "big mess" point now.

Good luck.
Keep us posted.

P.S. Be really, extra careful with jacks, stands, blocks, etc. when under the car. A lot of really bad injuries happen that way.
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Old 07-26-2011, 08:19 AM   #8
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Quote:
It looks like the new exhaust piece wont be too bad to replace so I'll be ordering that in the next couple days.
[IMG][/IMG]

Here's a picture of the Cat pipe. You can see the flex joint will need to cut off and a new one welded back on.
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Old 07-27-2011, 12:33 PM   #9
peterdemski
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

small update.

I stopped at the dealership and picked up a new gas cap. Not sure if the code will clear on it's own or if I have to go to the auto parts store to have it reset to see if that was the reason for the code.

I took apart the air tubing up to the TB and cleaned the carbon off of the TB around the butterfly. I noticed that the PCV tube doesnt have a clamp where it connects to one of the air boxes and seems to come off very easily. Not sure if this is by design or not. I didn't see a MAF sensor at all. I did see a MAP sensor which appears to have a good vacuum line and also a sensor of some sort at the elbow between the air filter and the air box on top of the TB.

I will be getting the exhaust fixed in the next week or so and hopefully that should take care of the other SES code and get the light to go off.

Driving it a couple of times today it appears to run significantly better but still will chug a little in overdrive on the highway you just have to press the gas a lot more than you used to for it to act up. The car is still hard to start with some movement of the gas pedal required for it to fire up unless it's completely cold(sat overnight).

So any more ideas while I wait for the new exhaust piece?
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Old 07-27-2011, 05:44 PM   #10
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Default Re: '99 Malibu 4cyl hard start/hesitation/miss

Quote:
Originally Posted by peterdemski View Post
So any more ideas while I wait for the new exhaust piece?
Two thoughts come to mind after your latest post:

Mis-firing when under load is often a sign of "spark leak".
New plug wires and boots might be in order.

And I almost hate to mention this but.......with 160K and part of the CAT assembly having worn out (the flex joint), you might be having a partially plugged converter.
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