Back to shop ↗
THE HOLDEN COMMODORE FORUM

HOLDCOM Community

Built around the cars. Kept alive by the people.

+ Start a discussion
Holden Commodores gathered at Holdcom
Forum Home›Technical help
Technical help

afm cas spark idle problems? read this

Started by duz360 · 8 Apr 2006 · 61 replies

Preserved from CalaisTurbo. Original authors and dates are shown; archived members are not current Holdcom accounts.

duz360Archived member
i just found this info while browsing the net. NO SPARK VL COMMODORES System uses an LED crank angle sensor (CAS) within the distributor to generate a speed signal (360-degree for timing) and a position signal (120-degree signal) for the computer (ECU). The ECU then uses these 2 signals to generate a trigger to the power transistor (PT) bolted to the outside of the distributor. The PT uses this trigger to switch the -ve coil to ground to generate spark. On top of the distributor is a 4 pin harness plug - this is the crank angle sensor. With this plug removed test the voltage on each pin of the female harness plug against ground (engine earth/battery -ve) with the ignition on (KOEO). Should have 12v (battery volts from the EFI relay), earth (Ov), and on the remaining 2 pins - 5v on each (from ECU). Ensure the distributor shaft is turning during cranking - cam belt. With the engine cranking these 2 wires which had 5v on each are the important signals you are after - expect approx. 2.3v on one and 0.3v on the other. If the CAS has failed expect close to 5v OR close to 0.0v on one or both. If the signals are BOTH within 20% of specs., then Check the signal from the ECU to the PT (fawn wire onto PT). If ECU is generating the correct signal expect approx. 0.4v. If a greater voltage, then you have an earth problem. If 0.0v then the ECU is not outputting the signal - ECU failed. If correct signal but still no spark then the PT has failed to switch the coil (rare) or the coil has failed (common). To check the PT is switching the coil, use a normal test light from the +ve battery to the -ve coil (brown/red at PT). Your light should illuminate with KOF (ignition key off), and when the coil is switched to ground through the PT during cranking. If your test light flashes during cranking then PT is doing its job so coil has failed. If no flashing then PT has failed. Or if test light constantly lit, then PT has failed. ROUGH IDLE VL COMMODORES A common problem with the 3-litre Nissan engine is where the idle deteriorates to the point where it will not even run. Before that happens there is an initial loss of power, which just gets worse. A prime cause of this is the Air Mass Meter drifting beyond specifications - check the load pin (3rd in from back of engine - white wire) against an earth should have KOEO no less than 1.26v (excessive lean) and no more 1.32v (rich). If this load setting base is out, you won't be able to adjust the idle mixture (1st pin in from front of AMM) factory lean at 3.6v to richer say 2.0v to a satisfactory mixture - AMM will need replacing.
0 likes
trypsiArchived member
Do we have sticky
0 likes
duz360Archived member
there is a rule saying i cannot sticky my own thread lol
0 likes
JET-6Archived member
But i can!
0 likes
dimplesArchived member
sounds like wat mite be the prob wiv my car thanks guys good find Some original photos have not been recovered yet.
0 likes
Dan_84Archived member
yeah ive done 2 cas, and 1 afm. pain in the arse!
0 likes
vlturbo33Archived member
hey im ahvin the no spark problem at the moment i have pulled the cas put of a dizzy that wasnt in very good nick can i test it with out goin 2 da trouble of puttin it in n finding out it dnt work thanks
0 likes
13FLATArchived member
I was under the understanding that the higher the voltage between the number 1 pin and earth when you were moving the idle setting the richer ie 3.36 to 3.38 was a move to make the car richer ? It has always seemed to be correct when I have been fiddling with the afms that I have touched ? What is the go ?
0 likes
SLO.BT1Archived member
somebody please help!ive just swapped in an rb30et, and have no spark.it has new plugs, leads,cap,rotor button,have tried 2 coils, one which definately works,3 cas all proven to work,2 different power transistors,and it has voltage at the coil,and correct voltages at the cas with the key on.also tried 2 ecus, one which was working perfectly when removed 2 days ago, one working perfectly a few months ago.any suggestions?please?
0 likes
HoldenOnArchived member
I had a Formula VLT which I sold last year which was runnin 12.3sec 1/4 miles with stock ECU and one extra injector controlled by microfueller. My tuner told me the settings for the AFM which I used to always stick to and it was perfect. Here are the settings; Pins 2 & 6 (Ignition on but engine off) - 3.6 volts Pins 2 & 3 (Engine running at idle and normal operating temp) - 2.2 volts ** Reducing Voltage Increases Richness **
0 likes
SLO.BT1Archived member
so the afm has something to do with spark?i have another one there that ill swap in to try.anything else please tell cause im desperate!
0 likes
HoldenOnArchived member
I dont believe the AFM is related to spark. My post was just to give knowledge to anyone in regards to the AFM.
0 likes
DVLISHArchived member
i dont understand which pins you test...the ones on the afm itself or on the plug?
0 likes
HoldenOnArchived member
While the AFM is plugged in, slide the boot back on the plug, then push the probes of the multimeter into where the wiring goes into the plug.
0 likes
Bec@AznewArchived member
Hey Guys I used to work at a place called INJECTRONICS in Hallam Vic. They deal in reco AMM and also sell a heap of CAS's. We sold a heap of VL AMM!!! If you guys are having trouble diagnosing give them a call they have a FREE technical support help line ... the guys there Steve and Shannan will be more than happy to help you out.
0 likes
magArchived member
Quote: Originally Posted by HoldenOn I had a Formula VLT which I sold last year which was runnin 12.3sec 1/4 miles with stock ECU and one extra injector controlled by microfueller. My tuner told me the settings for the AFM which I used to always stick to and it was perfect. Here are the settings; Pins 2 & 6 (Ignition on but engine off) - 3.6 volts Pins 2 & 3 (Engine running at idle and normal operating temp) - 2.2 volts ** Reducing Voltage Increases Richness ** Hey which way do the pins run?? 1 2 3 4 5 6 OR 6 5 4 3 2 1 My AFM is a Bosch unit but has N0 pin numbers but some are numbered so I've been told.. Some original photos have not been recovered yet.
0 likes
magArchived member
Anyone know the pin numbers on the AFM, pin 4 and pin 5 don't mean **** if you don't know which 1 is which Some original photos have not been recovered yet.
0 likes
theVLguyArchived member
all your AFM info http://wiki.r31skylineclub.com/index.php?title=AFM Some original photos have not been recovered yet.
0 likes
magArchived member
[QUOTE=theVLguy]all your AFM info http://wiki.r31skylineclub.com/index.php?title=AFM That's fantastic VLguy thanks Wonder why mine hasn't got the pins numbers Some original photos have not been recovered yet.
0 likes
magArchived member
Crank Angle Sensor, if you replace it you must do the top bearing too!!! Because that's the most likely thing that killed the CAS in the 1st place.. Buy the kit and it has the CAS of course, new rubber boot, 4 terminals, plug, bearing and instructions... Some original photos have not been recovered yet.
0 likes
Sign in or create an account to reply. New members are welcome—no purchase or old CT account needed.

Who’s online

0 members and 0 guests active in the last 15 minutes

No signed-in members active right now. Guests are welcome to browse.

Visitors Today13

33,602 threads, 484,230 posts and 19,609 images saved from CT

98.1% of indexed threads saved