2004 3.4L Alero With a Couple of Problems

[Jmalbright]

I have a 2004 Alero with a 3.4L engine and 4T45-E automatic transmission that is experiencing a couple of issues. I'm not sure if the problems are related. It does not seem like they are to me, but I thought I would post them both here just in case.

I'd first like to mention that the car is not throwing any trouble codes.

The first issue is related to how the car idles once it is warmed up. After I have been driving for a while and I get caught at a stop light the car will idle fine for a little bit then it will stall out and the rpms will drop significantly. Most of the time it recovers and does not completely die, but it has died a few times. Again, this does not happen until the car is completely warmed up and it happens intermittently. In order to try to solve this issue I have removed and cleaned the throttle body, replaced the IAC valve, cleaned the MAF sensor, and checked for vacuum leaks (just did this visually and by ear and did not find anything that seemed abnormal). None of this did anything to resolve the problem. So, at this point I'm not sure how to proceed and any suggestions would be appreciated. The last thing I wanted to mention that may be related to this problem is that my battery is on its last legs and needs to be replaced, but I haven't been able to do so because of tight finances. I know it is on its last legs because its voltage is low (around 12.3V, it is an Optima Yellow Top and should be around 13V) and the car is sluggish to start (normally takes a few seconds of cranking).

The second issue occurs on the highway and is most noticeable when cruise control is activated. Basically, the problem occurs when I have just eclipsed the top of a hill and start to go down the other side. There is some sort of hesitation/resistance where it almost feels like I tapped the brakes firmly. There is no noticeable change in rpms on the tachometer and no noticeable change in speed on the speedometer either. This has been occurring for a few months and seems to be getting more pronounced as time goes on. However, the condition is intermittent at best. I'm not sure, but it seems like this might be related to the transmission (this has happened in both 3rd and 4th gears). The car has 80K miles on it and I had the tranny flushed and filter changed at 50K. I also checked the tranny fluid and the level was fine and the fluid seemed to be in good condition. Without any trouble codes I am really at a loss as how to proceed so, again, any ideas would be appreciated.

I apologize for the long-winded post, but I wanted to be as detailed as possible. Thanks for your time.

[gmtech1]

First things first, replace the battery and check the charging system, volt meter should read around 14.0 volts at the battery with the car running. Low voltage will cause all kinds of problems.

[Jmalbright]

Originally Posted by gmtech1

First things first, replace the battery and check the charging system, volt meter should read around 14.0 volts at the battery with the car running. Low voltage will cause all kinds of problems.

I've been wanting to get a new battery for a while now, but I'm currently unemployed so I've been putting it off as long as possible. I am aware that almost everything is electronically controlled in this car and, as you said, low voltage can cause a whole host of issues.

I checked the charging voltage at idle (~750 rpm) with the alternator cold and it read at 14.4V so the alternator should be fine.

I just had a job interview and if I get the job I'll definitely get a new battery right away. Besides that, are there any other likely culprits that come to mind for either of the problems?

[autojoe]

if I had to guess.......I would say the battery is not doing this.the extended crank yes maybe.12.3 volts Is engine off no load voltage I imagine......what is your charging voltage?after car starts it runs off your alternator.I have seen crank sensors and ignition modules do this.trouble codes are just a start if there is any.looking at scan data and understanding what you are looking at is more important than just codes.lots of times especially on older vehicles codes are not there.

[Jmalbright]

Originally Posted by autojoe

if I had to guess.......I would say the battery is not doing this.the extended crank yes maybe.12.3 volts Is engine off no load voltage I imagine......what is your charging voltage?after car starts it runs off your alternator.I have seen crank sensors and ignition modules do this.trouble codes are just a start if there is any.looking at scan data and understanding what you are looking at is more important than just codes.lots of times especially on older vehicles codes are not there.

Well, I just got a job offer this morning, so I am going to pick up a battery this afternoon. You are correct. The 12.3V reading is with the car off and the car charges at 14.4V while idling.

Just to be clear, you're talking about the complete ignition control module and not just the coil pack, correct?

Also, there are two crankshaft sensors on the vehicle. A 7X sensor that installs to the engine block and a 24X sensor that installs near the crankshaft harmonic balancer. Which one is more likely to be at fault here? According to the factory service manual, after installing either of the sensors, it is necessary to perform a system variation relearn procedure which requires a scan tool. So, I'm not sure if I'd be able to do this myself because I only have a generic scan tool and not the GM Tech II scan tool.

Anyway, I'll replace the battery later today and report back if that resolves any issues.

[autojoe]

see how battery works.......I dont believe in just replacing items without proper testing......cost a lot of money that way.if you had a scan tool to look at crank sensor counts.also iac info.do you notice a rough idle or any other problem?no stored codes?do you have a tach and if so with warmed up is your rpm lower than normal?

[autojoe]

I found this tsb that may be related...........



#04-06-04-063: Engine Idle Flair When Clutch Depressed or Decel Stall (Reprogram PCM) - (Sep 1, 2004)
Subject:Engine Idle Flair When Clutch Depressed or Decel Stall (Reprogram PCM)

Models:2003-2004 Chevrolet Cavalier
2004 Chevrolet Classic
2003-2004 Oldsmobile Alero
2003-2004 Pontiac Grand Am, Sunfire
with 4 Cylinder 2.2L Engine (VIN F - RPO L61)

<A href="http://gsi.xw.gm.com/newsi/showDoc.do?docSyskey=1548273&from=bcpi#N65563">Condition


Some customers may comment on an engine idle flair when the clutch is depressed. Also, some customers may comment on a low speed engine decel stall when coming to a stop.
<A href="http://gsi.xw.gm.com/newsi/showDoc.do?docSyskey=1548273&from=bcpi#N65572">Cause


The flair may be caused by the vehicle entering stall saver mode when the clutch is depressed. The low speed engine decel stall is produced by an interaction between the engine control software and the IAC motor.
<A href="http://gsi.xw.gm.com/newsi/showDoc.do?docSyskey=1548273&from=bcpi#N65581">Correction


Reprogram the PCM with the latest calibration available.
The new calibration will be released beginning with TIS satellite data update version 6.0 for 2004 available June 2004. As always, make sure your TECH 2® is updated with the latest software version.


Labor Operation



Description



Labor Time



J6354


Engine Control Module - Reprogram


0.4 hr

[Jmalbright]

I picked up a battery yesterday and I was pretty disappointed to find out that it made no difference. The car still suffered from hard starts and all of the other issues I listed.

So, today, I decided to start testing what I thought to be likely culprits. I started with the fuel system and the fuel pressure checked out ok. I then started the car and pulled the vacuum hose off the fuel pressure regulator and, sure enough, fuel started gushing out of the vacuum port on the fuel pressure regulator, indicating it had gone bad. I did not even consider the fuel pressure regulator initially because I had already replaced it before and when it went bad the last time the car did not exhibit any of the above mentioned symptoms. It just reeked of gasoline, but this time there was no gas smell.

So I picked up a new fuel pressure regulator and installed it and now the car starts super easy. Its idle is also very steady and quite smooth again. I drove it on the highway some and I did not notice any hesitation/resistance with the cruise control on like before. I have not driven it enough to declare, with absolute certainty, that everything is completely resolved, but that appears to be the case so far. I have to say that I'm feeling pretty relieved right now because I was beginning to think that I was going to have to do some extensive diagnosis and repair work to get the car functioning properly again.

I know a lot of people have terrible opinions about this car, but I have 86K miles on it and got it when it only had 10K miles and the only things that have gone bad are the two fuel pressure regulators and the multifunction switch. So you can say I've been quite pleased with it overall.

Thanks to all who helped.

[autojoe]

thats great that you got it fixed.a good scan tool is great to have to find problems.if you work on your car a lot you might want to get one.your short term and long term fuel trim numbers would have reflected the leaking fuel pressure regulator.That is one of the first things I look at on scan data pids.