03 Saturn L300 Missfire, no accel

Everyone loves a happy ending. Share your diagnostic success stories here.
Post Reply
Posts: 3
Joined: Sat Mar 26, 2011 1:36 am

03 Saturn L300 Missfire, no accel

Post by gonzotr »

This Car runs decent at idle, not great, just off idle, it starts running rough and missing, Surging, sometimes backfires at full throttle. Wont accel above 2K.
There are no codes, no missfire codes, but #2 counts miss some. Cam Active Counter is good at idle, 85 and 170 #'s, durring accel, #'s drop to single digits. This would be considered and hard fault according to PID explenation, but no code, WF looks great too.

Cat's are not plugged, Vacuum is at 17 at idle, Drops hard on accel. Throttle body is acting normal. This poor thing has been apart before, now we get it, of course. Unplugging MAF makes little difference. Unplugging CMP, dies fairly fast, this should not occur. Once it is running, should stay running, till key cycle. We are missing Amp and inj. events as you can see. I see no reason for this, save the PCM. Physical check of grounds is easy, OK. Some noise in the timing cover, but this stupid Saab is a 10 hour timing cover job with special tools. Only thing that bothers me, the GIF show the degrees that the Cam is off from the Crank. I think it should be 90 degrees. Alldata says 900, but that cannot be right. 2.5 time crank revs. Hmmm. I interpret this to be 90 degrees. So do I tear down the timing and waste a day or two. I still don't think that explains the missing events. http://members.iatn.net/file/view/?id=53557&detailed=1

I continued to do some research, looked at Saab's stuff for this engine too. It is a Turbo, a little different, but I saw some interesting info. One stated the CKP Ohms. The timing does not make sense, but I decided that I was not going to tear down the timing until I threw a CKP in it. That took a week to get in. I can't help but thing there should be better info for this, but it was not to be.

Saab info:
"The voltage from the crankshaft position sensor varies with the engine speed. At idling speed, the voltage is 5-10 V (AC) and at 2500 rpm , 15-20 V (AC). However, it is the frequency and not the voltage that is of interest to the control module.

As soon as the control module receives pulses from the crankshaft position sensor, it will ground the fuel pump relay.

Sensor resistance is 860 ±90 ohms ."

The CMP dropout in data would indicate a CMP failure, but the car should run on double fire just fine. However, all my scoping, not one breakup of the CMP.

Well, This is the end of the story. I threw a CKP in it, Done!
Old sensor Ohme'd at 466, new one, 900. Runs good, Vac. is 19.5, Trims are +- 3, Good power.
Here's the new sensor WF.
Rollin_L300_Cam_Crank_#1ign._Coil 1 AWF_newCKP2.psdata
Full Capture, idle to 3K
(3.38 MiB) Downloaded 460 times
Close up of WF, no drop out.
Close up of WF, no drop out.
I think what was happening, was the CKP was dropping out right after the flywheel gap, and this was lwtting the ECM lose track. It was not sufficient for the ECM to set the code however. IMHO.

Pico Staff Member
Pico Staff Member
Posts: 337
Joined: Mon Jan 31, 2011 11:22 am
Location: UK

Re: 03 Saturn L300 Missfire, no accel

Post by PicoMike »

Thanks for the the submission. Hopefully other members will soon follow and add to the knowledge base on the forum,


Mike Valentine
Direct Sales Manager: Pico Technology

Post Reply