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only firing on 4 cylinders...


AutostradaVR4
06-10-2010, 06:35 PM
97 SL ATX
Not firing on clinders 3 and 6; no voltage to that coil.

I've checked:
Plugs
Wires
Coils
PTU
ECU
Timing

..so i guess the CAS is the next best guess.

So where exactly IS the CAS...and how do i test it?

Any other ideas?

also, where is the timing mark on the crank pully? Cams are all aligned but i didnt see a mark for the crank and dont know where i should be looking.

AutostradaVR4
06-10-2010, 07:23 PM
UPDATE!
Ok, it looks like the timing of off by about 30 degrees at the crank, which as best i can figure is 2 teeth at all the cams.
So what's gonna be the easiest way to fix it? I was thinking, get the cams TDC, throw my cam lockers in, slide the belt off (not sure how hard that will be), rotate the crank to TDC and slide the belt back on the cams.
is there a better/right way?
and before anyone speaks of bent valves...i did drive this thing home ~15 miles in it's current condition...slowly lol. It ran like shit, like running on 4 cylinders-shit, but not like bent valves-shit...so before i pull off heads im gonna try a quick fix.

also, what would cause the belt to slip? should i be checking anything else?

$STEALTH$
06-10-2010, 07:36 PM
Have you tried doing a manuel test diagnostics on your car?

AutostradaVR4
06-10-2010, 10:57 PM
mmmm...no? what is that?

$STEALTH$
06-12-2010, 02:22 PM
Here i want you to go to this site... Read everything that is on the page.
http://www.ecmtogo.com/ECMTips2.htm Your car is doing the same as mine... But only 2 of mine are working. But they are staying open when i turn the key on. It might be the computer thats my bet. This will tell you how. What to use. Let me know how it turns out

AutostradaVR4
06-12-2010, 03:17 PM
alright how do I check the cam position sensor?

the car doesn't have ECS so it aint that. Also, i inspected the ECU and there's no visible damage or leaking caps.

rhandwor
06-12-2010, 06:20 PM
Do a compression test on the cylinders that are not firing. Check if the injectors are getting signals use a noid light. Check for power to the injectors.

AutostradaVR4
06-13-2010, 12:06 AM
What's the compression test for? not even thinking about the possibility of bent valves right now,just looking for the cause of the problem. Would the cam position sensor effect the injectors signal?

not being skeptical, just curious how the CAS/CPS system works. Also, i have the thing torn down to fix the timing right now so i wont be doing and turning of the engine for the time being. would timing being off 2 teeth cause a coil not to fire? or should i suspect the cam angle sensor?

rhandwor
06-13-2010, 05:50 AM
Low compression will cause a cylinder not to fire. The sensors monitor a sprocket and a bent or broken tooth will cause a misfire. Bad wiring or a bent or loose terminal is a more probable cause. Most coils can be checked with an ohm meter. I would ohm each wire from the computer to the coil. Check for a bad ground. A bad injector will cause a cylinder not to fire.
I stopped at a friends garage and a Mazda had a misfire. Put in a spark plug ground the plug if it fires its probably an injector. This one had fire so they installed a new injector and it started firing.

AutostradaVR4
06-13-2010, 02:11 PM
there's no voltage to the 3,6 coil at all. I will start tracing wires if the timing fix doesnt solve it...not sure how im gonna do that though, as the leads on my multimeter are not nearly long enough lol.
So i guess for the cam sensor the only way to really test is it to make sure the wires look good and that theres no broken teeth.

rhandwor
06-13-2010, 04:20 PM
It takes two people but you can use a long piece of copper wire. A small gem clip for the connectors.
Make sure you check the plugs first. Generally the computer trips the ground to fire a coil and you should have a full time hot when running. http://www.alldata.com/ Has good wiring diagrams print off. A years service is appx. $29.95.

Stealthee
06-13-2010, 10:57 PM
Low compression will cause a cylinder not to fire. The sensors monitor a sprocket and a bent or broken tooth will cause a misfire. Bad wiring or a bent or loose terminal is a more probable cause. Most coils can be checked with an ohm meter. I would ohm each wire from the computer to the coil. Check for a bad ground. A bad injector will cause a cylinder not to fire.
I stopped at a friends garage and a Mazda had a misfire. Put in a spark plug ground the plug if it fires its probably an injector. This one had fire so they installed a new injector and it started firing.
No compression has nothing to do with a coil not firing.

If its only not firing on one coil pack its usually a cam ro crank sensor at fault.

To double check its not just a faulty coil pack switch it out with one of the other ones. If it fires on another set of cylinders and 3 and 6 still dont fire then you are on the right track.

AutostradaVR4
06-14-2010, 02:20 AM
yea i triple checked the coil...whichever coil is on the 3,6 spot gets no volts.
So it could be the crank position sensor as well? damn, i wish there was a way to test them without buying a new one for 80 bucks...
I did inspect the blades/sprockets that run through the cam/crank sensors and they seem fine...

Stealthee
06-14-2010, 09:00 PM
Well I have a cam sensor. I had it sold, but the kid backed out. $36 shipped if you want it.

91STT
06-15-2010, 12:03 PM
Probably not the camshaft sensor since it should on regulate the timing of the injectors. That crankshaft sensor controls ignition.
Have you checked the wiring between the ECU and PTU and between the PTU and the coil.
If you have an open in either of these wires it will not fire.
Check with an ohmmeter between the PTU black/white and 3/6 coil blue/yellow, it should be about 0 ohms.
Also check PTU brown/red to ECU brown/red (pin #11), this wire should also read about 0 ohms.

exoticnsx
10-05-2010, 09:56 PM
Do a compression test on the cylinders that are not firing. Check if the injectors are getting signals use a noid light. Check for power to the injectors.
Hey guys have the same problem on my 1995 sl 5 sp federal , i changed everything and also tried 2 ecu all the wiring is good so now i am thinking to try to check the cam timing or the cyl test like you guys talked about , i live in Atlanta so if somebody close by knows how to check these things i will gladly pay so i could drive the car again . Thanks

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