2000 cavalier mid range stumble

[Ratman667]

I have a 2000 Chevy Cavalier 2.2 OHV 5-speed with 91k.

When I take off from a dead stop, the car pulls fine, stumbles, then pulls hard again. I don't have a tach, so I can't tell what RPMs this happens at. The stumble feels like the fuel is shut off or someone is holding the brake.

I accelerate with about 25% throttle.

Engine modifications are: HAI and a PCV catch can.

Plugs and wires are AC-Delco and have less than 8 thousand miles on them (gaped to 0.050). I replaces both O2 sensors at the same time. The air filter is a K&N that is serviced every oil change (5,000 miles).

I am removing the HAI and catch can, to see if it helps any.

So far, I have cleaned the air intake, performed an induction service and visually checked the plugs. The only other remedy I cant think of is sending the injectors out for cleaning.

Any ideas?

Oh, I forgot to add, my gas mileage has plummeted. From low to mid 30s to mid 20s...

[GasSavers_BEEF]

what about fuel filter. I have a 1997 cav and it is in the rear. it took all of 10 minutes to change it (most of that was finding it) and it cost around 7 bucks.

also, my mileage went down due to a clogged EGR but that finally threw a code so I don't think that is the deal

are you throwing any codes???

*edit*

I noticed that you have been playing with a grill block. you can block the entire thing. I have the same car and you can cover the whole thing. take a look at some of my pics and you will see what I mean. you can do it a little less permanent than mine but it won't hurt your cooling a bit. at the same time, it is your car so do what you think is safe.

[Ratman667]

I forgot to add that I replaced the fuel filter and fuel pump about a year ago. Both are from the dealer.

It isn't throwing any codes, so that is why it's confusing me so much.

I am going to block the grill better, but I'm gonna get fancy with it. I'm gonna get another bumper from a junk yard, cut some pieces out of it and weld them in the holes.

[bowtieguy]

you might want to check your coil packs. because you have only 2(i have 4), they shouldn't be too expensive to replace.

[Ratman667]

I'll check that tomorrow.

[theholycow]

I think the fact that it's not throwing any codes may be diagnostically quite significant. Have you drive without the HAI yet?

[Ratman667]

Originally Posted by theholycow

I think the fact that it's not throwing any codes may be diagnostically quite significant. Have you drive without the HAI yet?

I have had the HAI on it for about a year now and it just started acting up about two weeks ago. Either way, the HAI is off and it didn't change anything.

[Ratman667]

It is the coil packs. I closed the gap on the plugs and the problem nearly went away.

Does anyone know of a way to test the coil packs without buying a new one? I would like to know which one to replace before I go out and drop $60 bucks on a new one.

[GasSavers_BEEF]

the poor man way would be to go to a junk yard and get one off of a blown car. it would probably be cheaper and you could use that for troubleshooting purposes and replace the bad one with new parts if you so desired.

maybe just rock the junk yard packs for a while.

glad to hear it got figured out (good find on bowtieguys end)

[theholycow]

There is a way to test coil packs. I think you measure their resistance.

Ah, found it:

Ignition Coil Pack
TESTING
2.2L (VIN 4) Engine

1. Remove the ignition coil(s).
2. Using an ohmmeter, check the resistance between the primary terminals on the underside of the coil. The resistance should be 0.50–0.90 ohms.
3. Check the resistance between the secondary terminals. It should be 5000–10,000 ohms.
4. If the coil failed either test, replace the coil.