TheSamba.com :: View topic - Need help diagnosing car problem (not VW)

Mon May 19, 2008 7:53 pm

My daughter's '02 Chevy Cavalier has developed a "surging" problem. While driving at constant speeds the engine seems to surge slightly. Sometimes you can watch the tach increase/decrease 200-300 rpms. It seems to do it at varying speeds. This occurs when the cruise control is on too.

The car only has 65K miles and is in otherwise tip-top shape. The engine runs smooth, it just hunts around the rpm's a little bit. Its not consistent either - sometimes it doesn't act up at all. The transmission seems to operate fine as well.

I haven't connected it to a code reader because the check engine light isn't on, and I don't think it will show a tripped code.

Ideas, suggestions, appreciated. Thanks!

Mon May 19, 2008 8:11 pm

Throttle postion sensor?

Tue May 20, 2008 3:41 am

vacuum leak?

Tue May 20, 2008 4:25 am

Its a chevy?

Tue May 20, 2008 5:31 am

Does it have a mass air flow sensor? If so, clean it w/ carb cleaner. Also, look for air leaks between the MAF and the throttle body.

Tue May 20, 2008 5:47 am

check to see if the car is equipped with an Idle Air Control/bypass valve... you'd be surprised how it can cause surging at any rpm... the seat of the valve can get covered in carbon and won't seal well causing surging... pop it out, clean the plunger with carb cleaner and the seat with a Q-tip and carb cleaner and it will be like new... also as suggested check the MAF if equipped.

Tue May 20, 2008 8:00 am

Lot of good places to start listed above. TPS. IAC. MAF. Vaccume leaks (EGR) let me add a simple one. Fuel filter.

Tue May 20, 2008 8:57 am

ID CHECK THE VOLTAGE AND MAKE SURE YOU CHARGING IS GOOD and full 13.5-15 volts, also o2sensors....i think there are two, tps is a good one and then the MAF, check simple tune up items too. clogged injectors or bad one check ohms resistance....can run lean and cause hunting too. vacum leaks of course. but at that age of the Chevy im guessing plugs or o2 sensor. also CATs can be a reason if old and hollow.

Tue May 20, 2008 12:36 pm

420GOAT wrote: ID CHECK THE VOLTAGE AND MAKE SURE YOU CHARGING IS GOOD and full 13.5-15 volts, also o2sensors....i think there are two, tps is a good one and then the MAF, check simple tune up items too. clogged injectors or bad one check ohms resistance....can run lean and cause hunting too. vacum leaks of course. but at that age of the Chevy im guessing plugs or o2 sensor. also CATs can be a reason if old and hollow.

Just load a bowl, sit back and forget about it, man. It's just a car, you know?

Tue May 20, 2008 1:04 pm

im tryin' brother but im stuck in this office till 4 pm.

Tue May 20, 2008 1:08 pm

the-jerm wrote: Its a chevy?
Exactly what I was going to say.
I'll ask my friend... Hes a Chevy guy and swears that the Caviler is the best Domestic Small car. lol

Tue May 20, 2008 1:21 pm

BadBeetle wrote: the-jerm wrote: Its a chevy?
Exactly what I was going to say.
I'll ask my friend... Hes a Chevy guy and swears that the Caviler is the best Domestic Small car. lol

So your friend is on crack, eh?

Tue May 20, 2008 4:16 pm

Rowroy wrote: BadBeetle wrote: the-jerm wrote: Its a chevy?
Exactly what I was going to say.
I'll ask my friend... Hes a Chevy guy and swears that the Caviler is the best Domestic Small car. lol

So your friend is on crack, eh?
Maybe? Every once in awhile he says if he had to get a Small car he would get a Cavalier. lmao (Hes ANTI VW other than the TDI's)

Tue May 20, 2008 7:15 pm

the-jerm wrote: Its a chevy?

Hey now, go easy... :wink:

Tue May 20, 2008 7:24 pm

BadBeetle wrote: Rowroy wrote: BadBeetle wrote: the-jerm wrote: Its a chevy?
Exactly what I was going to say.
I'll ask my friend... Hes a Chevy guy and swears that the Caviler is the best Domestic Small car. lol

So your friend is on crack, eh?
Maybe? Every once in awhile he says if he had to get a Small car he would get a Cavalier. lmao (Hes ANTI VW other than the TDI's)

Hey, that's what I had heard too and that's why we checked them out. This was my daughter's first car and she didn't want a VW. They are economical (over 30mpg) and the Ecotech engine that it has is said to be a workhorse that will easily go a couple of hundred thousand miles.

One weird thing is that the transmission is sealed up from the factory. You don't check the fluid as there's no dip stick.

Let me know what your buddy thinks. :D

Thanks everyone for your great suggestions. 8)

Wed May 21, 2008 1:08 am

we had this kind of problem on my mothers chevy venture van (not the same engine, but youre describing the same kind of thing) the voltage regulator in the alternator was going out (you can see the lights dimming back and forth at night) and a mechanic guy i know said it might have been messing up the computer and causing it to surge back and forth at specific throttle settings (in our case). after a complete tune up and alternator replacement, she hasn't had it happen again. though it could have been something covered in the tune up as well.

but it sounds like you're having the same kind of problem. it seems common among the chevy's. ive heard of a few people having this happen.

Wed May 21, 2008 7:14 am

VdubDreamer wrote: it seems common among the chevy's. ive heard of a few people having this happen.

Hmmm, I see. . . :-k

Wed May 21, 2008 8:18 am

VdubDreamer wrote: we had this kind of problem on my mothers chevy venture van (not the same engine, but youre describing the same kind of thing) the voltage regulator in the alternator was going out (you can see the lights dimming back and forth at night) and a mechanic guy i know said it might have been messing up the computer and causing it to surge back and forth at specific throttle settings (in our case). after a complete tune up and alternator replacement, she hasn't had it happen again. though it could have been something covered in the tune up as well.

but it sounds like you're having the same kind of problem. it seems common among the chevy's. ive heard of a few people having this happen.
i had a stroker tpi IROC that would surge when my buddy sold it to me , first off the voltage can not be less than 13 volts minimum, i took out the sounds, replaced the battery and adjusted the tps, it idled! i took care of a lot nore but that was where i had to start.

Wed May 21, 2008 5:22 pm

sounds like either the throttle pos sensor or possible mass air.

Thu May 22, 2008 1:50 am

anyone else get the blown seals from the dexcool antifreeze? that crap cost us an engine.

we were coming back from a trip to Branson, MO and around springfield we had a seal / lifter problem that quickly turned into a shattered piston problem..

it started as a faint tick-tick noise and after 2 seconds it became BANG Knock knock knock...

found out after the fact that it was caused by the coolant eating away seals, and causing many other problems. one of the oil seals blew out and dumped oil all over highway 63. theres a pending lawsuit about it. from which everyone involved will probably get a coupon for a current model year Chevrolet Craptacular. and chevy wont have to really pay much of anything else.