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'99 Malibu 4cyl hard start/hesitation/miss

37K views 98 replies 11 participants last post by  piticoto 
#1 ·
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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#2 ·
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.

RwP
 
#5 · (Edited)
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. :eek:
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.
 
#3 · (Edited)
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.
 
#4 ·
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.
 
#6 ·
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.

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.


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
 
#7 ·
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.
 
#9 ·
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?
 
#10 ·
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.
 
#14 ·
I was planning on ordering the CAT today and wanted to makes sure I ordered the right one. I was looking at rockauto.com and they have 3 from $160-210. I was wondering if anyone had any experience with any of these and how well the 'exact fit' is. I also wanted to take off the heat shield on the manifold and check the bolt pattern before ordering the new CAT as it appears the EGR cars had a different gasket and the CAT's at rockauto appear to have the non-EGR connectors on the flex conneciton.

So any tips for getting the three rusted on bolts off the heat shield without snapping them?

Also any suggestions for a reasonably priced CAT that you've had good luck with that fits perfectly?

Thanks!

P
 
#15 ·
#16 ·
Or get a can of CRC Freeze-Off Super Penetrant from your auto parts store. I used it to get a brake caliper bolt loose, then the axle nut, both on a 2000 Impala. Works great, and no heat or flame needed.
 
#18 ·
#20 ·
I doubt the injector cleaner did anything as my drive to work is <10mi however replacing the clogged air filter with a fresh one was likely the improvement I saw.


Felt around the exhaust manifold this morning before work and my car has the 3 bolt pattern connector. I'll be ordering that today with any luck.
 
#24 ·
Hmm it appears to now be out of stock everywhere it was priced for $150-175. Checked RockAuto and Partsgeek. The local stored will order one for close to $250 but I'd rather save the $75 and spend it on a O2 sensor if I end up needing one. Anyone have any other reputable parts places that might have it in stock you could suggest?

Thanks!

P
 
#27 ·
Advance Auto has a flagship ad for $30 off $150 or more, and since you won't need to pay shipping, that MAY be cheaper than RockAuto was.

The secret is to order online for pickup ;)

RwP
 
#28 ·
Looks like Parts Geek got some in stock so I ordered one this morning. $11 for ground shipping isn't bad at all and I found a $3 coupon so $157 total after shipping isn't bad at all in my book. Will look forward to getting it and finally getting another thing out of the way on the car.
 
#30 ·
I've been wondering lately if the strong fresh gas smell coming from the exhaust on the car when it first starts may have caused some issues with the CAT. I normally crank the car for a few seconds then stop to avoid wearing out the started but the last couple days I've cranked if until it fired without using the gas pedal. This can take 20 seconds or more depending on how grouchy it is. So apparently the car will start without hitting the gas pedal but it takes a lot longer. The car also seems to smoke a little when started this way for the first 10 seconds or so.

I'm just worried that I'll get the new CAT on and it'll get ruined in a few thousand miles because the engine isn't running right. Is this something I should be concerned with?
 
#31 ·
I'm just worried that I'll get the new CAT on and it'll get ruined in a few thousand miles because the engine isn't running right. Is this something I should be concerned with?
Yes absolutely. If liquid gas is getting in there, it might not take that long.

What's more, if you have an injector sticking open and dumping liquid gas into one cylinder when you shut it off......or when first starting.......or anything else making it run REAL rich like that........you may be getting gas in the oil which might damage the bearings and make the engine go BOOM.

Any time a fuel injected engine takes more than one or two revolutions to start, there is a MAJOR problem brewing. Is there any chance that your air intake is partially obstructed ??
 
#35 ·
Sure sounds like an air restriction. But, it could also be a stuck fuel injector or fuel regulator not regulating. Somewhere, you're not getting the correct a/f ratio. I just changed the fuel injectors on my kids 98 Malibu and that's a job I dont wish on anyone. Some would say that a massive vacuum leak could cause the problem as the computer would drive the injectors to supply much more fuel. Essentially, you'd be getting so much fuel that the car couldn't burn it all.

P.S. I never found a schrader valve on the fuel line in the engine compartment.
 
#36 ·
Another interesting note is that the car will start up normally(immediately) the first time if it has sat for a couple days. Since I was gone for the weekend it sat from Thursday night until Monday morning. Turn the key and it started right up. It is also colder in the morning but I'm not sure if that makes a difference. Went to PT to work on my shoulder for an hour(8 weeks post op) and it starts crappy again although I didn't notice the smoke is has had when starting lately.


Since I was gone all weekend I didn't have a chance to play with the car but the new CAT got here today. Need to go check it out at lunch as the G/F said there were two large holes in the box.

I'm hoping that your kids 98 was the V6 then and that the little 2.4L won't be as bad. I haven't looked for a place to hook a fuel pressure gauge in just yet but that's going to be looked at in the next day or two.

Can anyone let me know what static fuel pressure should be for the 2.4L motor?
I'm also looking for voltage at the injectors and the resistance of the injectors if anyone happens to know those off the top of their head :) Might as well start with that as it's easy to check.
 
#38 ·
Picked up a few maintenance items for this car this weekend including a chiltons manual so I had torque specs and at least some info on the specifics of the car.

Since I have been suspecting clogged/gummed up fuel injectors I picked up a bottle of both Lucas Fuel injector cleaner and Seafoam. Dumped the Lucas in a 1/4 tank and drove it around and dumped the Seafoam in this weekend when I filled up.

Starting the car is not significantly improved but the driveability of the car once started is significantly improved. I can still force the car to stumble on the highway in overdrive or when going up a hill by giving it gas to put a load on the motor but not have it downshift however I have to push farther now. If the injectors are really bad and do need to be pulled and cleaned/rebuilt does anyone know a good place to send them to?

As I ended up spending my wrenching time on the washing machine this weekend I didn't get to pull plugs or clean the TB although I did finally get some TB cleaner for when I have the time.
 
#39 ·
Had a few minutes tonight to pull the air box out and try to check the air piping that connects to the air box on the car. I pulled the front part of the wheel well cover off to find a twisted mess of molded hoses. I'm not sure what that part is actually called or where it actually sucks air from as I ran out of time and had to put it back together.

Was hoping someone on the board could let me know where this actually comes out or someplace I could see a diagram of it? I do have the option of removing the elbow that connects the air box to the moded air thing in the fender to see if there is some kind of restrction in there.
 
#40 ·
Had some time this weekend to pull the TB and give it a real cleaning and replace the TB gasket. Checked all the vacuum lines to the TB and they all looked good. wiggled the injector plugs a little to make sure they were seated good but should have measured the injector resistance while I had the TB off.

At first I thought I may have solved the problem as the car fired right up a couple times. Took it for a test drive and once it warmed up a little it had the same problems it had before however that eliminates a dirty TB or leaky TB gasket from the list of possibilities.
 
#48 ·
A very long ongoing issue with the G/F's '99 2.4l Malibu. It starts hard. Much more so when hot. You get a strong fresh gas smell from the exhaust when it finally does start and some blueish smoke. The car hesitates, stutters, etc when accelerating. It seems to be more pronounced when starting from a stop and also seems to get worse after the car warms up. It is also chugs/stutters when the engine is put under load. The easiest way to reproduce it has been to get on the highway and after it finally shifts to overdrive you press the gas enough to load the motor but not enough for it to downshift. The motor will stutter for a bit then usually downshift and seem fine once the RPM's are up. The car currently needs some exhaust work done and I have a new CAT w/flex pipe in the trunk however I didn't want to put it on until I fixed the raw gas in the exhaust so I didn't burn the new CAT up.

So far I've:
1. removed/cleaned TB and replaced TB gasket
2. replaced air filter
3. Replaced fuel cap(gas vent code)
4. Ran a couple tanks of Lucas and Seafoam through the car
5. Fuel pump & filter replaced(under warranty from a shop as last pump was put in just over a year ago)
6. plugs/boots/wires done by G/F's dad about a year ago.

It was my G/F's father car and I cannot vouch for it ever running properly although it has gotten worse in the last year. The hard start and driveability issues may be completely separate.

I do remember winter last year when the G/F was trying to get the car unstuck from our parking lot. I noticed quite a bit of black smoke from the exhaust as well as some coolant on the snow. The car does seem to go through coolant regularly and I have to add some a couple times a year as the light comes on.
 
#49 ·
Kind of hard without having the car in front of me. I would check two things, an injector balance test, seeing how much pressure drop is occuring from injector to injector. That and/or an injector coil test. Maybe an injector just dumping fuel. No check engine light? Sounds like it does it all the time? Correct? If you pull the plugs, any of them stand out from the rest? Looking for a wet plug or a real black one indicating rich mixture. At that point if you find one that looks like I said, swap the injector with a cylinder that looks good. If the problem follows the injector, pop an injector in it. Understand?
 
#52 ·
Ironically The low coolant light flashed at me going up a hill Friday on the way home from work. Sometimes there will be a few drips of coolant under the front passenger side area near where the overflow is. I am not sure where it is leaking at as it doesn't happen consistently and seems to know when I'm dressed up and cannot roll around under the car and look. I have done a few oil changes on this car and never found any coolant in the oil.

I am not sure how to do an injector coil test but I can pick up a fuel gauge and do the injector balance test. I can also pull plugs and see if any of them are very different from the others.

There were two SES light codes: P0440 & P0420
1. The CAT not working properly as the exhaust leaks at the flex joint.
2. Gas vent to atmosphere code. Apparently normally it says 'minor' normally but this one didn't.

I have a new CAT ready to install so that should take care of the first code and the leaking exhaust. I had replaced the fuel cap to try an fix the second code and had them reset. The SES light just came on the other day so I will be headed to the auto parts store to see if it's just the CAT code or if the second code is still there.
 
#55 ·
Sometimes there will be a few drips of coolant under the front passenger side area near where the overflow is.
That might not be a real leak but an overflow caused by marginal overheating.

This whole story worrys me because you have let it go long enough now that you might have THREE or more fairly major problems brewing......and the symptoms might mask each other and confuse things, making the final fix(s) a lot more difficult.

If you continue to drive it, there is also a (hopefully small) chance of a major failure. The longer it goes, the higher the odds get.

Good luck. I think you might need some.
 
#53 ·
Suggestion? Pick up a code scanner so you can scan at your leisure.

Second one? Go a step up if you have a Windows Mobile or Android cell phone - pick up a Bluetooth adapter and get full datalog capabilities while you're at it.

(#2 is what I really recommend, but understand some folks aren't that interested, and would rather pay $22 plus tax now than $54 and get the adapter in a month ... )

RwP
 
#56 ·
Had a chance to stop at the auto parts store today and have the codes scanned. I had looked at the OT-2 scanner some time ago for another vehicle I drive. has anyone had any experience with one of these? I don't have a smart phone so I'd need to use a laptop to datalog which is fine. I had just worried about the logging rate of the cheaper scanners.

There were two codes:

P0141 - New
P0440 - came back

So apparently the gas cap wasn't the issue. Is there a way to test the purge valve/solenoid to verify they are faulty besides replacing them and seeing if the code comes back?

For the new code, P0141, is says bank 1 sensor 2. My assumption for this was that it was the 2nd O2 sensor after the CAT. Is that correct? If so I would expect it to go away after I fixed the exhaust.

Rainy day today so no looking under the car or having the hood up in the driveway. Hopefully tomorrow I can pull the plugs and see what they look like.
 
#57 ·
So apparently the gas cap wasn't the issue. Is there a way to test the purge valve/solenoid to verify they are faulty besides replacing them and seeing if the code comes back?

For the new code, P0141, is says bank 1 sensor 2. My assumption for this was that it was the 2nd O2 sensor after the CAT. Is that correct? If so I would expect it to go away after I fixed the exhaust.

Rainy day today so no looking under the car or having the hood up in the driveway. Hopefully tomorrow I can pull the plugs and see what they look like.
You can tap on the vent solenoid and see if dirt falls out. Doesn't take much to bind up the pintle inside. Without bidirectional control from a scan tool, you can't really properly test the circuit. 12 volts is available on the brown wire to both EVAP solenoids wth the key in run but ground is supplied by the ECM when commanded, not there all the time.
The same fuse feeds the EVAP solenoids and the O2 sensor heater. The ERLS fuse in the underhood fuse block, check to see if it's blown, if not, make sure there's 12 volts there, preferrably a test light.
The O2 sensor code is a heater circuit code, the exhaust issue won't be an issue. Power is on the brown wire and ground on the black wire. You're checking the harness side with the key on.
 
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