Lurching/RPM drops in 03Cavalier!


#1

I have a manual transmission, 2003 Chevy Cavalier with 197,000 miles. Car has been great up until 6 months ago. My husband is great with keeping up with oil changes/ routine car maintenance. The reason for my post is, I am having two main problems with my car 1.) signifiant drops in RPMs while stopped. 2.) lurching while on the accelerator. The signifant drops in RPMs occur while at a complete stop and do not occur at every stop, it seems completely random. This first started roughly 5-6 months ago, my husband replaced the spark plugs and it was running fine until last week. Same symptoms- while at a stop it fluctuates between an idle of 1000rpms down to almost 0 (car has never died, but sounds like it comes close). The second set of symptoms have been fairly consistent the past 2-3 months. At first I thought I had some bad fuel so I applied fuel treatment- seemed to solve the problem until I filled up again. Same problem- again treated with fuel treatment, and issue resolved. The same tank of fuel got down to 1/4 tank, and symptoms started a third time. Again- fuel treatment. The car is now down to 1/2 a tank and the lurching has started once again. There is no way I continue to get this unlucky with bad fuel. The car lurches forward more when I maintain a higher speed (50-60mph) but on occassion can occur while going much slower. It typically jerks for 5ish miles, it doesnt occur my entire drive to/from work (22miles). My check engine light is on, but has been for years. Any ideas?? This is my daily driver, I depend on this car and am nervous if I dont find out what is wrong- ill end up stranded. Thanks for any advice.


#2

I’m sorry, but I find a disconnect/contradiction between the following two statements:
“My check engine light is on, but has been for years” and “My husband is great with keeping up with…routine car maintenance”.

Ignoring a lit-up check engine light for years=lax attention to maintenance, IMHO.
If that offends you or your husband, I’m sorry but that is my opinion, and I’m going to go out on a limb in order to state that many of the other veterans of this forum will likely agree with me.

Anyway…the first thing that you need to do is to have the OBD system’s stored trouble codes read. If the CEL has been lit up “for years”, I predict that there will be more than one, and you could wind up with a list of…perhaps 5 or 6 Diagnostic Trouble Codes. You can have the codes read–gratis–at a place like Auto Zone, Advance Auto, O’Reilly, or (possibly) Napa.

Until you get those trouble codes, nobody can give you a firm diagnosis, but if I had to guess, I would guess that the Idle Air Control valve (IAC) and the Mass Air Flow Sensor (MAF) are both extremely dirty. However, that is just a guess from afar and even if I am correct, there could well be other issues in addition to those two.

Get those codes read, and then come back to this thread, post the codes, and some of us will probably be able to give you more specific advice.


#3

Thanks for the advice. I will get the new codes today. I was not clear before. I have had the codes read in the past. Bad sensors were what they came out as, I believe 02 sensor. I have not had the car reassessed since the new symptoms started.


#4

With the CEL on thst long, you could have newcodes that may point to the problem. However, your symptoms are also consistent with a partially clogged fuel filter. These are often ignored in today’s cars, but, given the mileage, cannot be discounted. There is no code for fuel pressure problems, but you may get a’ lean condition’ code.


#5

A “lean condition” code (mentioned by BustedKnuckles above), btw, comes from a report from an O2 sensor. You can’t ignore any codes - but certainly not codes for O2 sensors. Well - ok. You can. But your car won’t run well…

When you post the codes, btw, post the exact code form like “P0123.” Verbal descriptions don’t work. There is, for instance, no code that can tell you that a sensor is bad, O2 sensor or otherwise.