BrettLinton7

iTrader: (33)

My newest FC has started to give me trouble lately. It started when I was trying to diagnose why the car was hitting the 3800 wall. I had swapped over the secondaries, the boost sensor, and the injector resistor pack from my other FC to see if that wouldn't help. Since the car was made in 11/86, I tried re-grounding the boost sensor but that changed nothing. After swapping all of this, the car still had the 3800 wall but was perfectly drivable under 3800 for a few days, but then it started getting this new problem. I swapped everything back out, injectors and all, and it's still cutting out.

Note: I'm not trying to fix the 3800 wall for now, just the cutting out issue. I've still got a few things to test for the 3800 wall myself. Do I believe the 2 problems are related? Possibly...

The cutting out problem happens when I'm driving and sometimes at idle. Just driving along, it will randomly cut out and not put out any power, like the engine is either not getting enough spark or an injector is stuck open. I think it could be one of those because I always smell gas whenever it does this, and I've gotten a few backfires lately. I believe it's no spark more than a sticky injector because if I press the throttle when it's doing this, it doesn't pick up at all. The only response I get when I press the throttle is when I first start to press it, the car picks up for 1/10 second and then doesn't put out any more.

Whenever this happens, normally when driving, I can turn the key off then back on (leaving the car in gear and the motor still turning) and it starts driving like normal. Then the car does the same thing after a second or two, so I do the key thing again. I can do the key thing twice or 10 times, and the problem eventually goes away for an hour/ few hours/ day/ days.

Also, when the car does this just sitting in the driveway idling, it will still idle but it's choppy and there's a hint of black smoke. I also noticed some black dots behind the mufflers on the concrete after the car had the problem idling for ~10 seconds. This is also something that makes me doubt the sticky injector because since it is behind both mufflers and it's a true-dual system, I know it's happening equally on both rotors and I highly doubt both primaries would be sticking... I'm guessing that the black dots behind the muffler are fuel mixed with the carbon in the exhaust...

And also, this happens under 3500 RPM's, so I'm ruling out the secondaries. For one, I can't take the car over 3800 because of the 3800 wall it's still having, and two, it still happens with the secondaries unplugged from the wiring harness. Also, the car's had this 3800 wall for a few years now and this new problem just started now...

I've got another FC here at the house that I can get parts from. Plus half of an FC in pieces at my uncles I'm just stumped.


Background Info:

I picked up an this FC from it's 2nd owner about 2 weeks ago. It's got 42K on a rebuild and a full RB true-dual exhaust, nothing else added for now.

The TPS is in spec, and all the grounds were professionally redone at a good known shop.

The ECU was replaced in 2005 (yes, the car's had the 3800 wall since then) so I'm ruling that out. The injectors could probably use a good cleaning, too.

All help is appreciated. I'd really love to be able to drive this without worrying about the car cutting out...

satch

iTrader: (1)

Something you can do is to check the Cas. See if it falls within spec when ohming out the proper wires at the ECU, and clean the CAS plug thoroughly. Also, while the car is running move around some of the relevant wiring harnesses and see if the engine behaves any differently.

BrettLinton7

iTrader: (33)

I'll give that a shot after class. You wouldn't know off hand where I could find directions for testing the CAS do you?

I've actually tried that a couple of times. I've unplugged and cleaned the TPS plug and plugs going to the coils, and wiggled a good bit of the harness/ other connectors too. Another shot wouldn't hurt, though.

satch

iTrader: (1)

At the ECU disconnect the middle plug (2nd largest one). Multimeter set to ohms one meter lead goes to pin 1N, Green wire, and the other meter lead to pin 1P, Blue wire, and the ohm reading should fall within the 110 to 210 ohms. Do the same thing with pins 1T, Red wire, and 1Q, White wire.

BrettLinton7

iTrader: (33)

Update:

I swapped the leading coil out with a spare and changed out the plug wires, mainly because the coil took only a minute and it had cheap plug wires on it. That didn't make any difference because the car started doing the same thing at idle.

So when it started doing it idling in the driveway, I started wiggling all the connectors. When I move the one on the water-thermo sensor on the back of the water pump housing, the car returns to normal.

So I'm assuming the connections there are no good. I'm going to clean that up and see if it makes a difference. If not, I've got a known good CAS that I'll swap in.

BrettLinton7

iTrader: (33)

If anyone else has this problem, it was my water-thermo sensor that was making the car cut out like this. A $15 one at Autozone solved the problem...