fast951

When you test/wiggle the wires, are they as hot as when it cuts out? When it cuts out, do the dash lights come on?

jerome951

While on the track this past weekend I left the DME and KLR lying on the floorboard in case the heat of the firewall or vertical orientation was making them act up. No change. Soon after coming off the track I moved/wiggled the wires to no avail, but they were close to operating temp. It wasn't overly warm this weekend (mid-80s), and actually the worst episode was in the cooler morning run. Only once did I run more than a handfull of laps at one time, and during that afternoon session the car only briefly hiccupped twice in 20 minutes.

When the engine cuts and quickly refires (as in the video I posted), no dash lights but a jumpy tach. However, when it completely dies, the tach doesn't jump around but the ! light does come on.

I picked up a code reader from Prack so will try that in a few weeks when I have a chance to drive it. Chris is thinking poor engine or DME ground so will test that when I have a chance to get the car nice and hot and look for a voltage drop.

fortysixandtwo

If forgot to physically check last night, but I believe there is a separate relay for the DME and Ignition.
A few weeks ago I had the same symptoms you describe. Tach would jump a few hundred RPM just as the engine cuts out, sometimes it comes right back to life, sometimes I need to crank the car to get it to start and other times it required me to let it sit for a while.
The root cause, in my case, was a faulty Ignition relay. One of the terminal rivets had loosened and would occasionally cut power to the relay's coil.

Papamurphdog

Ok, read your responses. You might still want to open the boot of FI connector that is most twisted or bent, just to be sure the wires have insulation and are not touching. Otherwise, if the tach is bumping that's good. The sensors are likely good. (I did replace both female sensor connectors as well BTW, mine were crapola.)

The Potentiometer-throttle position sensor (SP?) connected to the throttle body can also have a bad female connector (I'm changing mine next...) and I'm told it might cause symptoms like yours.

You can check the ground/power to the DME and KLR with a cheap multi-meter. Kill the battery and ignition switch. Pull the connectors for BOTH the DME and the KLR so each is already removed when you turn the battery back on. Turn on the ignition and on the DME connector test pin 5 to 35 and then 5 to 18, if you have voltage the groun/power if fine. Then test the KLR from pin 6 to 14 and 6 to pin 20. this will confirm power/ground to the units. If good then you have some other gremlin or the units are perhaps bad. The shop manual has other tests you can do.

Another poster suggested ignition relay and that might be a good fix as well. I am changing mine for the heck of it as it is old.

Good luck. This stuff is soooo frustrating. I have little hair left from my recent experiences...

jerome951

OK Guys. Wanted to revive this thread as I've done a little more troubleshooting. Thanks to all those who responded with their thoughts and experiences.

As I mentioned before, car cuts out abruptly. Sometimes completely dies but will restart. This typically happens under hard acceleration but has done so while cruising and idling. See my first post for parts I've replaced or swapped (pretty much everything).

Lately I've been tapping into the DME harness to try to figure out what is happening. I run small indicator lights from different circuits on the harness to see what is losing power when the engine does. Here's what I've discovered thus far:
- minimal voltage drop across the engine and DME grounds (i.e. few mv each)
- DME stays powered when the engine cuts out (I checked 2 power inputs from the DME relay) as I wanted to eliminate any upstream power interruption
- No KLR/DME error codes are thrown using the small 5-pin code reader in the engine bay
- Fuel injector signal from pin 14 is constant when the car cuts out (I thought the speed or ref sensor wiring was bad because the tach bounces, but I think this eliminates this possible cause)
- *** ignition signal to the coil (pin #1 on the DME harness) DOES cut out when the car cuts out. I found this out on the drive to work this morning.

So my questions:
1) What else would cause the signal to the coil to be interrupted? I think the speed/ref wiring is good based on my results of the fuel injector signal
2) Would a bad ignition relay as 46&2 above mentioned cause this problem or does the ignition relay feed directly to the coil?

theedge

A bad relay could cause problems yes. You can check the relay, and also when you do get a spade connector (one of the crappy crimp ones from Autozone/etc) thats the same size as the relay terminals, and try plugging it into each of the female sockets for that relay. Sometimes the female connectors in there get loose.

Spidey944

about all i can offer you is a full wiring diagram if you dont already have one. LMK.

jerome951

Thanks Brian. Do you happen to have a test procedure (i.e. what connections to bridge to override the relay)? After all this troubleshooting I have connectors of many sizes so probably have one that fits.

Oddly, neither Paragon nor 944Online carry an ignition relay.

Papamurphdog

Did you open the FI boot like I suggested? In my case the FI "clip" had power -- and pin 14 worked fine...but the wires were intermittently shorting inside the FI boot itself. Keep reading this post but you do not say if you actually opened one of the boots to inspect...

RPHARRIS

My car had that exact problem for a while and not just on boost. Turned out the DME chip was falling out of the socket LOL. One morning the car just plain wouldn't start so I popped open the DME and "WTF where'd my chip go!"

Check you speed/reference sensors and harnesses. Other than the cutting out, it sounds like its running really well!

Papamurphdog

Chip fell out!?! Damn, what else do we need to do to keep thesre things running! Funny stuff...adding that on to my list...

BRIT944TS

I have had several problems with relays recently, turned out to be bad / cold soldering on the internal connections. The relays can be opened (carefully with a small jewelers screwdriver) and resoldered. I think the solder that was used in those days is prone to stress cracking over time and the ends just lay against each other and cause intermitant function.

Just an suggestion.

jerome951

Thanks Guys,

I *think* I might have solved it. I didn't want to post again until I know for sure. The coil signal is definitely cutting out.

I swapped the ignition relay w/ the foglight relay (they're the same) and the seems to have fixed it based upon 1 test drive. I'm going to drive it again this weekend to verify (and put the old relay back in as a test) and let you know the results.

Thanks again for all of your ideas.

MooreBoost

fixed?

jerome951

The relay swap didn't cure it. I'm now in the middle of replacing the engine wiring harness. I'll know this weekend and will post when I find out...

If this doesn't do it I'm going to try running a switched hot lead directly to the coil and call it done...