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Gas Smell, Erratic RPM, Bad Gas Mileage, Loss of Power

Howdy y’all and thanks in advance.

I drive a Chevy S-10 truck, here are the specs:

4 cyl 2.2 liter SFI

The problem: Gas smell in the cab, erratic rpm at times when driving (tachometer revs but not accelerating), a seeming loss of power (when i accelerate, there’s a sort of “lag”, not much happens). Also i feel like my gas mileage has decreased severely (i haven’t confirmed with testing, but it sure seems like it). Heres what i’ve done so far–
replaced some decaying vacuum lines
replaced throttle position sensor (probably unnecessary, but oh well…)

In the recent past i replaced the radiator, which involved removed the air intake. I’m pretty sure i put everything back correctly, but I thought i should mention it. Anybody got any thoughts?

Thanks so much!

These 2.2 liters are notorious for having leaking injectors.

Pete “stole my thunder”. +1 to Pete’s post.

NOTE: there are other possibilities…are you sure all your cylinders are firing?

Ok, so i guess my next move is to test the injectors. According to my haynes manual, i need:

  1. stethoscope–or a screwdriver (might have to try this first)
  2. noid light–to check for voltage to injectors

As i understand it, this only tests for operation, not leaking. Is that correct? If so, how would you recommend testing for leaking injectors?

I’m not sure about the cylinders either–how would I go about investigating that issue?

That is correct.
Take them out and have a shop test them on the bench. Injectors can leak either externally via the outside seal or internallly by not fully closing when they’re supposed to. They can also be clogged in such a way that they splurt fuel instead of spraying it. Sort of like if you slowly pulled the lever on the Windex bottle instead of squeezing it quickly. That splurting can cause the fuel to burn very poorly and incompletely.

Do you have any stored fault codes?

Oh, and by the way, a vacuum on the intake leak will cause all of your symptoms except the gas smell. n exhaust leak upstream of the upstream oxygen sensor could cause rich operation and your symptoms. But you should be storing codes, and that’s the best place to start.

well, as a true amateur, i totally forgot about checking the fault codes. I’ll look into that post haste.

I had the codes read at autozone this morning and here’s what i got:

P0440 --EVAP

B0237–Rear wheel speed signal
B0227–Front wheel speed signal

The EVAP code certainly seems to be connected. So i guess i’ll pursue diagnostic testing. Any thoughts? Could i do some type of DIY cigar smoke test or something?

The other two body codes–i don’t know. I couldn’t find any info on them, and they don’t seem to be connected, but still…i’m not happy about them.

I took a look at the gas cap–the seal around it was cracked. So i replaced the gas cap and lo and behold a day later the CEL went off! It’s stayed off for about 3 days now. The gas smell is gone too. However, other problems remain–primarily the erratic RPM and a seeming loss of power/reluctance to shift.