My son in law & grandson borrowed my son's 1999 Miata for an autocross this weekend.
It was running great . . . until it wasn't.
My grandson hit a cone. Not hard, basically just clipped it with the driver's rear wheel and within 100' the car died. It coasted to a halt and we pushed it to the pit area.
We began to look for the obvious. There was no sign of damage to any wiring near the wheel. Actually we didn't really see any wiring there.
So we looked for plug wires, blown fuses, or basically anything else simple and something that would cause a sudden malfunction.
I found a broken nipple on a vacuum valve that was mounted to the rear of the intake manifold. The incoming vacuum line for the valve was from the very bottom of the intake manifold and it went to a large "pot" just behind the throttle. We plugged the lines and valve with gum because we couldn't find screws or anything else.
During this whole time the car would turn over and only occasionally hit once or twice, but never enough to even sound like it was starting. We weren't sure if that meant it wasn't getting spark often, timing was way off like an engine or timing control system or whether it wasn't getting gas. If it had jumped a tooth on the timing chain it would have hit more than it was hitting.
There were 2 mechanics in the pit and they came over and immediately looked at the CAS (Crank Angle Sensor). They said it looked to be gapped properly. A CAS issue kinda fit our theory of engine/spark control gone awry. They had no other good ideas.
Just after they left my son called and said he had an OBD reader in the car, why didn't he tell us an hour earlier?, and we got an 0339 code for CAS bad or intermittent signal so this seemed to confirm a bad CAS. Fortunately someone gave us a free tow home.
I spent Sunday afternoon getting the car up, the pan off and the CAS off. Finding and disconnecting the CAS was no big deal, but getting that wire unthreaded and off took as much time as everything else combined. I finally cut it. There's a push connector on the side of the electrical connector that simply won't let the wire fit through what holes it had to go through and it was impossible to remove, hence why I cut it.
Unfortunately the new CAS came with that same dumb push pin already installed on the side so getting it back on was going to be just as big an issue.
It was very easy to get the CAS itself bolted back in place and I read that I needed to set the gap from .02 to .059 so I picked the first feeler gauge size that came out which was .32 and set the gap.
I connected the CAS without threading it back through all they byzantine passageways the factory made for it, just to see if it would start.
I gave it a couple of cranks and nothing happened except the battery went dead. So was it not the CAS and there's something else wrong or was there just not enough juice in the battery to get me going?
Since I had to put the new CAS on anyway I spent the time to run the wiring. I would dearly love to find the engineer/designer that set this up, I'd B-slap him!!!
So my first question is how critical is the gap on the CAS? Is smaller better than larger?
While the battery was charging I took off the vacuum switch and set out to get a new one. The only thing I knew about this switch was that it was a vacuum switch and the mechanics in the pits said only the later cars with EGR had it. Coincidentally (?) my son had thrown intermittent EGR codes so without really paying attention to the location of the valve or what it was connected to I headed off to the parts stores.
I was able to stump the parts guys at 3 parts stores. The valve was a Mitsubishi product and without knowing what subsystem it controlled no one new what to search for. All of them had the same bad picture of the Miata engine with unreadable numbers telling you what the parts were. The closest looking part we could find was a picture of an Evaporative canister valve, but it appeared to have larger vacuum line connectors.
Of course we're not allowed to upload pictures so I can't show you our engine so I've had to find a picture on the web to link to. It won't have the lovely arrows and things mine would have had.
Approximately where this fellows hand is is where the vacuum switch was mounted. On this car there is no round pot for the vacuum line to hook to, but on the 99 it connects just about where all the other vacuum lines connect just behind the throttle.
So can anyone tell me what to ask for at the parts store?
