Hi Derf-
Since my last post, I replaced the spark plugs with OEM's, however, that did not fix the problem.
I'm hoping you can help make sense of the following condition that I noticed:
This condition happened three times, in exactly the same manner (so, the fact that it's consistent gives me hope in figuring out the problem).
1. After replacing the plugs, I reconnected the battery and erased the OBD code.
2. Then, I drove it for approx. 5 miles during which the SERVICE ENGINE SOON light did not come on.
3. I shut off the car, then restarted it about a minute later.
4. The car idled fine for about 10 seconds, then the engine "lulled" (kind of sounded like it lowered in RPM's slightly).
5. Immediately after that, the SERVICE ENGINE LIGHT came on.
6. The OBD code P0304 came back on.

What do you think? I would really appreciate your input/guidance, as I am kind of stumped and am frustrated since it won't pass inspection until this is resolved.
Hopefully, the consistent scenario (slight engine RPM decrease, shortly after restarting) is a clue for you.
Once again, thanks for your time.
Steve

 

P0304 or P0340 ?

 

The RPM drops when the PCM enters closed loop control. If sitting still in neutral or Park, it should drop to the expected idle. In neutral it would be 850 for a manual and somewhere between 700 and 800 RPM for an automatic. Is the engine stumbling once the RPMs drop? Are you getting a solid or flashing check engine light?

 

Sorry- it is code P0340 (not P0304).
The engine was slightly stumbling, once the RPMs dropped. I drove it another 8 miles and then the SERVICE ENGINE LIGHT started flashing. Also, the engine ran much rougher and it started smelling like something was burning just as i was arriving home. I shut it off and then restarted and the idle is now quite rough.

 

What codes?

 

Operation CHARM: Car repair manuals for everyone.
Home >> Saturn >> 2001 >> SC1 L4-1.9L SOHC VIN 8 >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0340

P0340

Diagnostic Chart:

Schematic:

The electronic ignition (EI) module supplies a ground to the cylinder #4 signal wire whenever it determines cylinder #4 has just fired on its compression stroke. The EI module uses capacitive pickup plates located under the 1/4 coil pack to determine the polarity sequence and voltage amplitude of the cylinder 1/4 secondary ignition. The PCM supplies 5 volts on the signal line and expects to see the cylinder #4 signal wire go low after every 14 crankshaft pulses (2 revolutions). This is used to determine the position of the camshaft, except under decel. The PCM only uses the transition from 5 to 0 volts as a valid TDC compression #4 cylinder signal. DTC P0340 sets when the PCM detects missing cam pulses (not seeing one cam pulse every two crankshaft revolutions).

DTC PARAMETERS
DTC P0340 will set if the PCM cam pulse has not been properly detected (cylinder #4 signal line not pulled to ground) for 136 engine revolutions when MAP is greater than 30 kPa.

If the PCM detects 20 correct cam pulses in a row, DTC P0340 will pass for the rest of the ignition cycle.

DTC P0340 diagnostic runs continuously until 20 correct cam pulses have been received when the vehicle is not in a decel.

DTC P0340 is a type B DTC.

DIAGNOSTIC AIDS
Use Scan tool to monitor CMP RESYNC COUNTER while running engine. The counter should count to 14, which indicates the number of notches passed on the crankshaft in 2 revolutions, then reset to zero when a cam pulse is received.

High resistance in the #1 secondary ignition system or low resistance in the #4 secondary ignition system can set this DTC. Check for corroded or loose #1 or #4 secondary ignition components. Use Scan tool to monitor MISFIRE CURRENT CYL. #1 and #4 which may point out an intermittent misfire causing the DTC.

A missing cam pulse without a cylinder misfire may not affect engine operation.
pro multis · About Operation CHARM

 

Misfires can cause the PCM to set the P0340 code. We need to verify codes and do some testing.

 

Indeed, I've asked him to read the codes after the flashing check engine light but either the misfire code does not show or the codes are not being read after a flashing check engine light and the whole thing is intermittent such that when the car is started an hour later, whatever is causing the misfire no longer seems to be present so he only gets a p0340 and no misfire code. I would suggest you leave your code reader attached to the vehicle while you are driving. Once you get the flashing check engine light, read the codes immediately. You should have a p0340 and one of the misfire codes I listed above. If you don't do this, there's no way for us to figure out where the misfire is. It's possible even this will not isolate which cylinder but there's a good chance it will.

 

Sounds now like you have a constant misfire so please read the codes again

 

Unless you disconnected the battery the modules store the codes. Get them.,