97 850 T5 now (apparently) running on 3 cylinders (ECT sensor wiring) Topic is solved

Post by **Chuck W** » 01 Feb 2019, 16:11

So, the T5 decided to get salty with me the other day.

About 5 minutes from home the car started to stumble a bit and threw a CEL then died on me as I pulled into a parking lot. I restarted it, drove back home checked codes.
P1310 - Misfire On At Least One Cylinder
P0303 - Cylinder 3 Misfire Detected
P0300 - Random/Multiple Cylinder Misfire Detected
I cleared the codes, restarted the car and it drove fine for the 25 minutes to work.

Coming home, it ran fine, but did start to stumble a bit about halfway home, then it cleared up and drove fine. No CEL/codes.

Seeing as it was acting up, I didn't drive it yesterday, but went to drive it today.(It was pretty damn cold here for a couple of days)

It started fine, but sounded a little stumbly. As it was sitting, it started to idle higher. I shut it off, and then it wouldn't restart. It would crank fine, but not fire.

I did a quick fuel pressure check, and it holds 42-43psi without problem. (Thought it might've been a failure if the feed hose in the tank off the pump, as I've had that happen before).

While it was idling, it sounded like crap. I did a quick pull of each injector connector, and the idle didn't change when I pulled #2 and #4. It threw a CEL for-
P0202 - Injector circuit open cylinder 2
P0204 - Injector circuit open cylinder 4

It's very hard to get started and actually popped/backfired once through the intake and pushed the dipstick out.

When it does start, it runs rough and will start to idle faster.

Up until Tuesday, the car was running fine. The last major work I did in it was the PCV service back in Oct (Did the "High-Mileage Mod" at that time.)

Plugs are about 10K old.

Thoughts?

Post by **misha** » 01 Feb 2019, 16:35

What spark plugs you put in it?
Cap & rotor condition?
I would check timing and if it's ok re-visit recent pcv job.
Check fpr vacuum line if there is fuel in it...it shouldn't be any.

I doubt that it burnt valves on both cylinders,but it could be that timing belt jumped and damaged them.
Re-check ignition parts first,fpr,timing...leave pcv re-visiting last....or just perform a compression test.

Post by **Chuck W** » 01 Feb 2019, 16:56

This evening was my first pass at diagnosis. Was short on time.

I was going to pull plugs and check cap/rotor/wires tomorrow.

Plugs are NGK BKR6EIX. I don't think I've messed with the cap/rotor yet. Timing belt is about 40K old (but I didn't do it).

I doubt the PCV job is a culprit, but I'll check. I repaired a "service" the PO did before I bought the car. I'm surprised it ran as good as it did for the 10K or so miles before I took it apart to fix it. He had NO clamps on any hoses, and none of the lower bolts on the intake were tightened at all. It was golden and correct when I got done with it. If that didn't cause any issues in the past year and a half, It would take something REALLY wrong now.

Post by **misha** » 02 Feb 2019, 03:31

Remove those iridium spark plugs and check gap...it's critical on turbo engines....or try with cheap copper Bosch or Ngk and gap them properly.
Cap & rotor could also be culprits.

Post by **abscate** » 02 Feb 2019, 06:00

Those codes were generated by pulling the harnesses off while running , not necessarily by fault.

Injectors are rare to fail on these cars, if the fuel pressure is up to spec, measured at the fuel rail, it’s ignition stuff.

Post by **Chuck W** » 02 Feb 2019, 06:59

abscate wrote: ↑02 Feb 2019, 06:00 Those codes were generated by pulling the harnesses off while running , not necessarily by fault.

Injectors are rare to fail on these cars, if the fuel pressure is up to spec, measured at the fuel rail, it’s ignition stuff.

Well, I know injector failures are rare, but I pulled the harness from each injector at least 3 times to verify. The only codes were for #2 and #4, which were also the ones that the engine showed no change when they were pulled.

I have a list of things to check when I get a chance to work on the car later today.

I'm leaning ignition-related, perhaps brought on by the severe cold earlier this week, but I guess we'll see.

WhatAmIDoing · Post by **WhatAmIDoing** » 02 Feb 2019, 12:53

Have you checked fuel pressure while running? This will sound odd, but I had a very similar incident happen. I was ripping everything apart trying to diagnose this intermittent misfire and stumble. When I was at my wits end, had the idea to replace the fuel pump relay... and that worked! Popped in a brand new relay and the problem immediately went away and never came back. It was the relay the entire time, despite the fact all tests indicated it was functioning properly. Replace the relay with a jumper and see if that does anything. It's an easy test that can save a tonne of headache.

Post by **Chuck W** » 02 Feb 2019, 16:19

OK, so I got into this today.

-Checked resistance of all injectors. All good.
-Checked plugs. All still gapped at .028", like when I installed them 10K miles ago. I'll swap them for something else later.
-Pulled dist cap. Only mild wear, but it was full of condensation. So I cleaned that all out. (As a note, cylinders #2 and #4 were next to each other on the bottom of the cap, so I thought perhaps I'd found something here)
-Swapped out wires with a set of Borgicord wires I was planning on installing later.(PO had installed some Autolite wires)
-Checked timing. It was bang on, and everything looked great, seeing as it only had 30K on it)
-Swapped ECU (-072) with another I had on the shelf.

After all of that, I go to start the car. Starts up fine, but I can tell it's still missing. It burbles and pops when I rev it, and as it warms up, the idle starts to hang after throttle blips. The when I go to restart it after shutting it down, it cranks forever and does the "pop" through the intake, if I'm too persistent about trying to get it to start.

Before I put tools away for the day, I check one last thing. I pull the connector for the ECT sensor, and find it to be mildly crusty. I touch up the male pins with some sandpaper and put it back together.

Car starts up and now runs fine. Smooth as it was and revs cleanly. Warm restarts are problem-free.

So, the culprit was the ECT sensor, or more specifically, the connector.

I had thought about it the other day, because this all happened when it got really cold. I'd disconnected and reconnected it, but didn't spend too much time messing with it, as it might've been 2*F at the time.

The car has always seemed to run a tad rich, but I just haven't gotten around to investigating the ECT sensor. I've got some work/upgrades to do in the spring, so I'll revisit the cleaning then, to make sure it's all good still.