Random Stalling

[fusiondude]

I know this has probably been answered before, but the topics I've run across have different odb codes. Well, here's what's up...

I got my GT back in 2006. Took it to the shop for an oil change, said the entire exhaust system was a wack-job and had it redone. Minus a slight noise sometimes at a certain RPM (which is another problem), new exhaust system seemed fine.

Couple weeks afterwards, Check Engine light pops up and it fires a P440 code. Didn't really think much about it since it went away after a few more cycles. Couple more weeks, comes up again and it's the same code. This time, it decides to stall every so often. And a little while after that it stalls big time. At lights, it felt like it would want to tear it self apart. Even sitting anywhere, it would stall and it would keep trying to clear itself.

Finally took it to a shop and turns out it was a bad fuel distributor. They replaced it and cleaned the intake manifold. Ran a lot better the next couple of days. No more stalling at lights... only now it just stalls every couple of cycles. These stalls can be cleared with a good tap on the gas though. Also, the check engine light also comes up every so often, but I clear it with a reader I bought. I don't think it's a vacuum leak because the guy I took it to said he did a pressure test and it came up fine. I haven't had a tune up in a while and I plan to soon. Should I consider another pressure test? Could there be something up with the IAC, EGR and so forth? Is there anything else I need to have checked?

Also, that noise in the muffler is around 3500 RPM, only it sounds like it's coming from the front, where the exhaust begins. Could there be a loose hanger or heat shield?

[rixGAphx]

'98 4-cyl, 10-yrs old, about 120k miles?

Previous code was P0440 Evaporative Emission Control System Malfunction, went away; returned, with occasional stalling.
Then stalling got worse (more frequent, I presume).

There's no such thing as a 'Fuel Distributor' on these engines, so I don't know what the shop replaced (at which time they also 'cleaned the intake manifold').
You say it ran much better, but still stalled at lights.
Frankly, I would have been all over them, that they had NOT solved the problem stalling regardless of what work they had done.

Perhaps they changed the Fuel Pressure Regulator?
$50 part that takes about 15 minutes to change, for which they'd charge about $200?
* * *

Prior to clearing the codes when the CEL comes on now, what are the actual code numbers?

Personally, I think you've got a leak in the Evap System, which is the tubing and components indicated on the decal on the passenger front strut tower.
This system isn't in constant use, it is actuated by PCM electronic signal to the purge valve only under certain conditions.
That would explain the randomness of the CEL and problem.
Also check the bizarre arrangement of tubes that serves as the crankcase ventilation/vapor control system, in lieu of a conventional PCV system.

You can't do a 'pressure test' on the engine to determine vacuum leak, though you can use the same vac/pressure tester to measure how much vacuum ('suction') the intake is drawing.
Due to the 'intermittent' nature of when the Evap System actuates, a manifold vac test might never show anything, even though there's a major problem.
Part of this system is a black plastic tube across the firewall, with a green-cpped test-port about in front of the passenger seat.
Perhaps this is what they 'pressure tested', rather than the engine itself?

A 'tuneup' for this engine consists of changing the plugs and their boots. That's it, nothing more.
If your platinum plugs have less than 60k miles on them, then there would be no benefit IMO.

I also think that one or more of your 3 motor mounts is/are broken, causing excessive shaking in the engine.
Inspect them, and replace as required.

Most inline 4-cyls develop a quirky 'harmonic' amplification to their exhaust, in the 3500-4500 rpm range.
Where the exhaut pipe drops under the firewall and turns horizontal, there's very little pipe-to-body clearance.
I *think* the 4-cyl is supposed to have a kinda corrugated flexpipe at this location, but I dunno for sure.
Anyhow, on all cars that pipe-to-body location is a prime candidate for contact and noise.
And a faulty motor mount or 2 or 3 would allow enough engine 'rocking' for contact to be virtually assured.

Hope this helps,
-Rick

[gtracing96]

I have a P0440 code on my 4 cyl. but my CEL is always on, and it has never stalled on me!

[rixGAphx]

Shawn and Kelly, please note that I am biting my tongue here.

[2K SE]

You done good rix. :D: