I Have a 1995 Cavalier 2.2 5-speed with just under 100,000miles only thing aftermarket is a 2.5 cat back with glass pack.
Has new plugs/wires Ran several tanks of fuel injector cleaner through the tank. New fuel filter.
At say 40mph at about 2,000rpms it misses and bucks a little, this is between say 1700 and 2,400 not bad but just enough to be annoying.
Compression is this 170, 170, 175, 175. 1 through 4.
Im thinking dirty fuel injector, other than that i dont know what else it would be. I did searches but really didnt come up with much so any ideas would be appreciated.
ok, installed header with 2.5 down pipe to stock cat with 2.5 out. Stock intake. Did nothing at all for me at all. Well anyways i still have NO code.
I checked all over for vacuum leaks, There is nothing(cant hear anything and starting fluid trick did nothing)
I checked TPS(i thought maybe it had a dead spot)NOTHING!!!!!works fine i think .55v at closed throttle and 4.8 at wot and a completely smooth reading up to WOT.
I need to check the MAP sensor and go from there.
Could the EGR have something to do with this?
Maybe a weak fuel injector?
Im only getting 18-22 mpg and i mostly drive to get good gas milage and average speed is i would say 45-50.
I had even better mileage with the s-10 with the 2.2l with 200,000 miles!!!!
Now im looking at a Haynes manual (i like Chilton better) but it says 1995-2004 uses obd2 but i know for a fact mine is obd1 if that makes any difference.
Please help me i even took it to several garages and they said they had no guarantee to whats wrong and would charge me no matter if they found the problem or not.
I am very inclined with this crap and im stuck
anything would be appreciated
fuel filter possibly? maybe a clogged injector. check compression in cylinders? or pressure if you can.
maybe you have a bad coil pack., im assuming you havent replaced them. see if you can get those tested. might be one of the problems.
New fuel filter, compression stated in first post. Fuel pressure not checked. might try swapping injectors to see if that does anything, Could it really be a coil pack going bad? i would think that would be constant.
Like i said it does it mostly when warm at a steady throttle like (1-4 to 1-2 inch down. guessing)...
I myself am still leaning towards a map sensor starting to go bad or something.
But thanks for the response and i will give you the information on what fixes it when i find the problem.
Well, I think ur just starting to have your ignition pack or packs go bad. My ecotec did that and it was only during a certain rpm. I would say change out the packs and go from there. If that don't work then it has to be the idnition module. Even tho u check it (I had my 02 ls sport on a gm tech 2 and it said everything was fine) it will say everything is still good. I had my car repaired under warranty and the ignition pack/module was bad. I would say change those, should fix the problem. Hope this helps!
Check the EGR.
EGR gives better light cruise fuel mileage.
Does is happen under full throttle? EGR is supposed to be closed at WOT.
Based on your findings, I would most suspect either MAP or EGR. It would be interesting to have an external vacuum gauge hooked up to watch to see what it's up to. That can be a handy diagnostic tool. That would probably allow you to see if it's running lean on one cylinder. Then all you have to do is figure out which one...
Too bad it wasn't OBDII - it may have made this a little easier...
Keep us posted. It's good to know the outcome of stuff like this for future reference.
John
ok here is what i did. I got a MAP sensor at the yard from a s-10. It must have been that because it does not buck and jerk anymore like it did, BUT i can still hear that it has a miss but not as bad as it was so i am happy enough.
Now it idles at about 850 witch it should be versus 950 like it was before.
Could that MAP just have masked my real problem(it does have different numbers on it)
I highly doubt this had anything to do with it but at the same time i changed the oil.(10w-40 not to thick right)
I just want to get it running perfect but who doesn't want their car to run perfect.
thanks again for all the help you have given me.
