I had a crack occur in the upper radiator hose today. This is a Discovery 1. The crack was maybe 4mm across, and I lost some coolant. The condensed steam alerted me to the leak and I stopped the vehicle almost immediately. Temperature indicated normal.

This was a replacement hose (PO bought non-genuine part from AB and since it was new I didn't reconsider their decision). I wasn't carrying a spare or silicone tape. I repaired it with a tire plug, checked the coolant level and attempted to return home a few miles away. But the engine would stumble and ran poorly. I checked for vacuum leaks, problems with plug wires, anything obvious. I found nothing. I tried limping home. In doing so, I had to pull over a few times. Upon restarting, the engine on two occasions ran perfectly for a couple minutes and then began to stumble again. The stumbling I'm talking about was such that the engine would idle reasonably well, but the more throttle I gave it, the more it would waffle, popping sometimes and it could only manage low speeds.

After I got it home, I pulled all the spark plugs and found them all normal. Oil is normal. I lost about a gallon of coolant, but after the initial loss, the repaired radiator hose was working very well.

The only suspicious clue I have is that the hose leak was such that it sprayed a jet of hot coolant directly into the multiplug for the engine coolant temperature sensor (I believe that's the one with two wires, and the fan switch is the single wire). I know the ECTS affects fuel mixture but it should only do so within a reasonable range and the ECU has a default value in case the ECTS fails. At least that's what RAVE says.

I normally carry a OBDII code scanner in my console, but I had borrowed it for another car. Unfortunately it was stolen out of the other car so I've got to get another one before I can read the codes. I'm sure I've got a bunch of misfire codes and besides that I don't know what. I did notice that the check-engine light was flashing at times. I've only ever seen it steady-on before.

At this point I've stripped all the rubber hoses off the top of the engine for replacement (I've got a new lower too but wasn't ready to dump all the coolant), and I left all the plugs out since I could use new ones. Once I get all new hoses on there, new plugs, I'm hoping the problem resolves itself. Of course, I bothered to write all this in case anyone has a better clue. Thanks

 

Hope you get it sorted out. Another possibility is that you also have a head gasket leak, which would contibute to the misfires. A chemical test can confirm if you have exhaust gas in coolant. Not sure of your year, but on the later D1's there are two sensors, one for ECU, as you said, two conductor, and one next to it for gauge.

 

Yeah, I hope it's not a head gasket. The ones in there now only have about six or seven thousand miles.

Does an ultra gauge use the ecu sensor or the gauge sensor signal? I just ordered an ultra gauge to replace the stolen ODB2 scanner. It was about a $40 scanner but the gauge will do way more for the money on this car.

I bought genuine hoses for everything except the two heater core and two intake jacket lines. I figure I can use straight line for those. I think my Napa has Gates or something. The original heater core lines are molded but the two little jogs they have don't seem to matter much. I did order the genuine reducing rubber that goes from the big nipple near the thermostat housing to the 90 degree metal pipe.

I try to be proactive about this stuff. I've had high-need vehicles before.

Ordered some silicone rescue tape too.

 

OBDII port uses the two wire ECT. Gauge uses the one wire sensor.

 

Everything got doused in coolant, rinse the entire engine with clean water, start it and let it idle until dry.
Then see what happens.

 

Ok, I replaced all 7 coolant hoses, all new spark plugs, and new wires (STI). Took a while to get the new upper hose from Vermont.

Sometimes it runs fine, other times it misfires, stumbles and pops. I'm getting misfire codes P1313, 1314, 1316.

It could be the leaking coolant damaged a fuel injector (it looked like it was spraying right into the ECT sensor), but if a fuel injector was sticking, the spark plugs all looked even.

Ultraguage shows me the the ECT sensor is working and temps are low. It doesn't ever go over 180.

Sometimes it runs smooth up to 70mph, other times its misfiring and stumbling so bad it won't go over 30mph. I'm looking for some kind of intermittent problem, not just a disconnected vacuum hose.

 

Could be a cracked hose, like one to fuel pressure regulator, etc. Also, that low temp may not be a good sign unless you are somewhere very cold. At 28F, 50 mph, my D1 with a 180 F stat can make 183 - 187F. If you have a stock 192-195 stat then you might have a stat sticking open.

 

Your VSS is bad.
And you are running to cold.
Did you replace the t-stat?

 

VSS eh? I'll have to look into that.

It's cold here, 15 deg. today. I'm betting the PO put in a 180 deg t-stat. PO was a indy Rover mechanic and he did the head gasket job and I bet he did that too. I'm pretty sure it's not sticking because the engine came up to 170 in just a couple minutes idling.

I did check the vacuum hoses, including the fuel pressure regulator. I'm not seeing a vacuum leak, but I notice the engine shakes a little bit when idling. I know it was smoother before. Now when it idles there's a little low-frequency shake. Not a motor-mount knocker, but it used to be very smooth.

I tried cleaning around injector 1 because it was very near the coolant leak. I removed the multiplug, and cleaned everything with a toothbrush and brake parts cleaner and blew it out with the air-compressor.

I'll look at it some more when it's not too dark or cold outside.

 

I pulled the multiplug on the VSS - sure enough busted the brittle clip on it too. I do believe disconnecting the VSS is adaquately diagnostic, no?

I also replaced all the vacuum lines now with new.

It's idling nicely but if I blip the throttle in the driveway I can hear it missing sometimes.

On a test drive it's able to get up to highway speed, but I hear it popping sometimes and other times if I give it throttle it sort of wallows and misses.

I ran out of time for further work/diagnostics on it so that's all I've got for now.

I have the beginning of suspicion of the fuel I put in there. I run premium, but I wonder if I got a bum tank. It's still 3/4 full.