98 GA, 2.4L, Intermittent Stalling

Hi all,

Looking for some help here. Appologize in advance for the length of this post.

Car is my daughters car, and it ran OK, not great but Ok. She complained of a Chk Eng Light, so I went and picked it up. Sure enough it had a Chk Eng Lamp on, but after driving it for 20 miles on the freeway, I stopped to get gas, and at the next Key On, the lamp cleared.

About a week later, it came back. I drove to Autozone, and they pulled code. Had a O2 Sensor Fault.

I replaced the O2 sensor and the code was cleared.

Then, the weird stuff started to happen.:confused:

When driving the car the next day, it stalled at the stop sign on my street. Started right up no problem, but it had a noticable hesitation, stumble and then stall. Creative throttle management could keep it running. Once it gets up to speed, it runs fine.

The next day, I noticed it again. Seemed to ONLY occur in Closed Loop (after warm-up). No codes or Chk Eng. Noting looks wrong, just stumbles and then stalls.

Took the car to a Firestone shop, it was a waste of time and $$$$. They found nothing and charged me $$ for the effort.

So I decided to dive in and do it my self.

I started by searching this forum... Lots of great advice for various items.

I decided to start by searching for a vacuum leak and then replacing the IAC and Fuel Filter. Upon removal and inspection, both were in bad shape. I also cleaned the intake and throttle body with cleaner. No vacuum leaks were observed. All hoses looked good.

Note:: There is no PCV on this engine. I was surprised, but it has a hose to the case from the air intake box. I guess this is normal.

Car did seem to run better and I thought I nailed it. But nope. Did the same thing. Stumbles and stalls. :shakehead

Next I replaced the MAP, TPS and cleaned the MAF sensors. I used the throttle body cleaner from Autozone. It did a good job removing the gunk from the throttle body and internal parts. The MAF sensor is impossible to find around here. No idea why noone carries it. Any suggestions on where to buy one?

No help, same problem. Still stalls.:banghead:

On Sunday, I plan to replace the Fuel Pressure Regulator and order the MAF ON-Line. I can post the results on Sunday after I do this.

So far I am $500 into this and still has the same problem.:confused:

Note:::: The weird thing is, it did NOT do this before the O2 was replaced. But, with the fault, I can only assume it was in a default mode and not in closed loop. I have no idea how long the O2 had been bad as my daughter only recently mentioned it.

Anyway, I am looking for some help, ideas, tips or tricks. I am almost at my end with car. It is for sale and I hate to sell it in this condition.

Thanks again for all of your help in advance.

Dave

Follow-up....

Ok, today I installed a new Fuel Pressure Regulator. Wow, that was a task in itself. While I was in there, I cleaned the injectors and replaced the O-Rings on each injector. After getting everything reassembled, I started the car and it ran good. I took it for a test drive and the Check Eng light came on.

Ran up to Autozone and pulled the code. The O2 Code was back:banghead:

Had it cleared, it did not come back. Now it ran GREAT. The best it has ever ran.

Got it home and shut off the engine. Let it cool off for about 1 hour.

Restarted it and wouldn't know it... it stumbled and stalled again as it warmed up.:confused: At this point, all I can do it cry...

Could it be a bad O2 Sensor that is causing all of this?
If the O2 is bad, not bad enough to set the code, could it cause the Engine to stumble and stall at idle? Could it casue it to run rough?

That's it for now. If I can't fix it soon I will enter it in the derby.

Dave

Welcome to AF !

Sounds like an ignition problem, plugs/boots or the coils & ignition control module-ICM hav a short.

That's where I would have started after the O2 sensor change. The other components you replaced should have set a DTC if they were faulty. :2cents:

You didnt mention which O2 you repalced, but I'd also change the secondary(downstream) O2 sensor if you didnt replace that one.

Also your 2.4 doesnt have a MAF sensor.

There is only the one O2 sensor...near the engine in the exhuast manafold.

Their is a MAF sensor and I took it out and cleaned it. Upon inspection, it looked very good and not dirty.

The IAC was definetly cloged and gummed up. I tried to clean it, but it was not able to be returned to a reasonable shape, so I replaced it.

As for a short in the coil pack or bad wires or boots, why would you suggest a failure like this? It seems to me if this were the case, it run bad all the time. Or at least mis or spit under load.

The car runs GREAT under load and at higher RPM. It is really only at idle it is noticable. It will start to stumble, and catch itself, RPMS will jump and it will settle out. Then do it again, and if it can not not recover on its own, stall.

Still debugging and ready to light it on fire.....:banghead:

Thanks for the feedback.

Dave

There is only the one O2 sensor...near the engine in the exhuast manafold.

Their is a MAF sensor and I took it out and cleaned it. Upon inspection, it looked very good and not dirty.

Got a picture of this MAF ?
In your first post you said you already replaced it along with other components, which or what did you actualy replace ??

The IAC was definetly cloged and gummed up. I tried to clean it, but it was not able to be returned to a reasonable shape, so I replaced it.


When you replaced the IAC did you calibrate it to 1 1/8" and clean the TB and the IAC port ???

As for a short in the coil pack or bad wires or boots, why would you suggest a failure like this? It seems to me if this were the case, it run bad all the time. Or at least mis or spit under load.

The car runs GREAT under load and at higher RPM. It is really only at idle it is noticable. It will start to stumble, and catch itself, RPMS will jump and it will settle out. Then do it again, and if it can not not recover on its own, stall.
On your ignition system, yes it could run fine under load because the power/voltage increase could over power the short.

Also how did you check for vacuum leaks ?

xeroinfinity,

Sorry for any confussion on the other post. Like I said, I got it now...

But as for this problem....

I checked for a vacuum leak but inspecting all hoses. I saw nothing ovbious. Then, with the engine running, warm, I sprayed some starting fluid around all intake areas (hoses, seams, etc..) at no time did the idle pick up to drop as a result. This implied to me, that no leaks were obvious.

Yesterday I started the car after it sat allday and it ran really bad, even when cold. When it got warm, to still ran bad. Smoked excessivly, smelled like unburn fuel, ran real rough.

Today, when I started it, it was cold and ran great. Ran great when it was warm. No excessive smoke and no smell. Drove it for a few miles, ran great. No stumbles and no stalls.

Now as for your question about the IAC setting.... You got me thinking... I know I read this advice in the manual when I installed the new IAC, but now I can not convince myself I actually did set to 1 1/8 before installing it???:shakehead

I need to pull it and check this again to be sure. Task for Wed....

The debugging continues....

Thanks again,

Dave

The intake bolts can get loose over time that was why I asked how you checked, you did it correctly.

Yeah sounds like the IAC isnt set right and or the passage it sets in is carboned up. Might pull the TB and clean it good.

Also when was the last time your fuel filter was changed ?
Even a clogged filter can cause such stalling.

Another thing what brand was the O2 sensor, and was a universal sensor ?

Yes, I changed the Fuel Filter, added injector cleaner and moisture remover to the fuel tank. I also cleaned the inside of the TB the best possible without removing it. Maybe I need to remove it. Is that a big job?

The O2 is a Bosh brand direct replacement unit.

The weird thing is the problem is now gone. Ilet the car run Wed, Th and Fr and agin this morning and never did it stall. No stall cold, no stall warm.:banghead:

I plan to remove the IAC today and make sure it is set correctly. I will try and clean the TB again/more and I will check the bolts on the intake.

More to come later.

Thanks,
Dave

Bosch is not OEM replacement, AC delco is and Bosch. You'll be lucky if it lasts a year IMO.

If its idling right and not stalling, then I wouldnt touch it right now!
Havnt you ever heard "if its not broke, dont fix it" ? lol

TB is pretty easy to pull off, might need to remove a few other things to acess the bolts nuts holding the TB on.

i would try this unplug your o-2 when it's running bad and see what it does?

Ok, on Sunday, I removed the IAC and checked the setting... It was < 1 1/8" so I left it alone. I again checked in side the well where it sits, it looks really clean. I opened the butterfly and looked inside, it looks really clean. Recall, I cleaned all of this last week.

I checked the bolts I could easily reach, and they were tight.

So far, still running great warm. Maybe the cleaning did it?????

Has a small stumble while warming up, wants to stall, but it does recover????

Took it out and drove it like I stoled it, ran great.
Drove it soft and easy, no stall.

Looks like now when it warm, it runs great.

A few days of testing and I will close this one out as fixed... Just wish I knew 100% the cause. Oh, well, at least now it is running well.

Thanks for every ones help and advise....

Dave