Rough Acceleration...

[Kimreeder]

I have an '01 GA 4cyl, 110k miles.
When I first start the car and accelerate, it seems to miss a little bit. It's like a very short loss of power and then it picks up after a couple smaller misses. This is consistent every time I start the car. Once the car is on the road, there's no real problem that I can tell. I've changed the plugs, fuel filter, both O2 sensors, and checked the codes with a scanner. It hasn't set a code at all. What should I do next?

[norbit2]

when was the last time you replaced the wires

[Matt95GT]

Start with ignition system troubleshooting, as it is frequently the source of problems on the 2.4.

Things to troubleshoot:
spark plugs (age, proper gap, brand - use stock AC Delco platinum plugs only, other brands will cause problems)
coil housing - check for signs of arcing or cracks
check plug boots for deterioration
bad connections to IDI module, etc

After that, coils and IDI module would need to be tested.


when was the last time you replaced the wires

It doesn't have any.

[Kimreeder]

Thanks for the info...one other thing. Someone suggested I let it warm up a little before I drive it, which I did...seems to help. And what's the possibility that it could be the mass air flow sensor?

[Matt95GT]

Thanks for the info...one other thing. Someone suggested I let it warm up a little before I drive it, which I did...seems to help. And what's the possibility that it could be the mass air flow sensor?

Warming up before driving is a good practice, but won't solve misfire issues.

That possibility is zero - the 2.4 doesn't have one.

[GrandAm2000se]

Shouldnt ever drive your vehicle unless it is warmed up, because all your doing is forcing the fluids throughout the engine. :(

[AeR0]

so what did the problem turn out to be?

im having the same issues sort of?

[gt00]

I've changed the plugs

use stock AC Delco platinum plugs only, other brands will cause problems :D

[Kimreeder]

I changed the plugs with AC delco stock plugs a month or so ago hoping the problem would go away. I had used those piece of crap Bosch plugs before - never again. When I changed the plugs, the car ran great for about a day, and then went back to doing the same old thing. I haven't checked anything else on the ignition system, but I never considered looking at some of those components. As far as now, it's doing the same thing, even in good weather, and I haven't had a chance to troubleshoot any further. I do believe I have a small leak in my power steering hose...gonna have to change that pretty soon too. BTW, when I changed the bosch plugs, even though they were under 20k they were really dirty. Thats why I changed the O2 sensors thinking I was having a problem with rich/lean mixture and getting some extra deposits. But the problem is still there.

[AeR0]

where abouts is the 02 sensor? and how much u pay for it?
and how hard is it to change?

[Kimreeder]

There's one sensor before and one after the cat converter. The first one is under the aluminum heat shield in the back of the engine. three screws to get the shield off and then the sensor is down a bit in the back in the side of the exhaust. Don't even bother trying to get it out unless you have an O2 sensor socket. Otherwise all you'll do is cuss. I used the "loan a tool" from autozone. you pay thirty bucks to get the tool and then they refund the money when you return it. The second sensor is under the car under the drivers seat in the exhaust pipe and it's real easy to get to.
The two sensors together (AC Delco) are pretty expensive but if you watch the auctions on ebay, you might find a deal (on new ones obviously). I got a pretty good deal on some new ones for about 125 combined. You just have to find the model numbers for the ones you need.

[rixGAphx]

Kim-

Check or just change your plug BOOTS as Matt suggested; they substitute for plug wires on the GA 4-cyls (as norbit meant to say).
If they're dirty, cracked, or 'carbon tracked', then the spark bypasses the plug and goes right to ground.
But since the spark complete its path, the engine never 'sees' a misfire so it doesn't set a code.
This would also explain why installing new plugs seemd to temporarily cure the problem.

A faulty Fuel Pressure Regulator is also common on a GA of this age, and won't show a code.
Do a 'suck test' (search) on its vac hose.
If it's leaking, then the pressure isn't being properly reduced at idle when the engine is still cold; so it doesn't respond properly when you you press the throttle pedal.
Once the system warms-up, the computer switches out of 'open-loop' to 'closed-loop' where it sets the fuel injection based on richness of the exhaust (as sensed by the front O2S).

Good luck,
-Rick

[Kimreeder]

Thanks for those replies everybody. That's some helpful info. I'm gonna go ahead and replace those plug boots first as I don't think it's much of a stretch anyway since the car has 110k. It can't hurt at this age. That's a really good explanation too, Rick, about the possible reason for the misfire. That answers a lot of my questions about why no codes were set...I've been baffled by that up to this point. Maybe that'll be an easy fix, other wise I'll try the FPR route.

[Matt95GT]

Just to add to Rick's misfire explaination...
The 2.3/2.4 ignition system also seems to be very "forgiving" about detecting misfires and setting a code. I've already had fouled plugs that were missing, loose IDI module wiring, or purposeful misfires (via MSD "stutter box" launch control) and I've never ever gotten a misfire code. This is also another reason why I favor ignition problems when people report stuttering issues but have no codes.

[rixGAphx]

Just to add to Rick's misfire explaination...
The 2.3/2.4 ignition system also seems to be very "forgiving" about detecting misfires and setting a code. Yeah, as I realize more about how the PCM responds to data it receives, I understand that it EXPECTS to see numerous 'misfires', mebbe 0.5% of the time!
If they're all on one plug, then it will *prolly* set a P030x code for that plug.
But if they're all over the place, then it looks at its tables and prolly says "My idiot GM programmers said this was 'normal' and I shouldn't set a code."I've already had fouled plugs that were missing, loose IDI module wiring, or purposeful misfires (via MSD "stutter box" launch control) and I've never ever gotten a misfire code.
This is also another reason why I favor ignition problems when people report stuttering issues but have no codes.Your wisdom is well-founded on facts and theory.

:D :D