Loss of Power/Stuttering Issue. Occasional No Start

[Lanval]

This post takes off on Nathan@el's title purposely, since we're looking at similar issues. For mine, first a lengthy narrative with occasional data points, followed by a summation. If you want to skip the narrative, go down to the summation which begins after the series of stars: ********************

Ahem ~

On Sunday last, I decided to take my kid to visit my brother, and test the van for a longer period. Mom wants me to come visit, and I was curious what the van would do for a longer drive at freeway speeds ~ 45min to 1 hr.

On the drive up, I was on the main freeways but not I5. There were a couple of points where the van stumbled ~ quick drop in RPMS, then back to work. When I arrived, the van wouldn't restart. I thought it might be a hot-start issue, but the van refused to start after sitting for 3 hrs. Checking around, I considered whether the neg battery cable was an issue. I usually just keep it setting on the post (poor man's quick release). So I pulled it off, cleaned the post and the inside of the terminal, an voila! Problem fixed. Started up just fine.

Cut to drive home ~ it's now after 10pm and dark. With the "rat's nest" (hah hah ~ inside joke. I've pulled multiple dead rats out of the engine bay while cleaning) of electrical problems, I was nervous. So I went home on the Pasadena/I5 combo which is quicker, but discovered a problem. These are older, well-used freeways with many bumps, potholes, and cracks.

As I drove along, I started getting cut-outs every time I hit a significant bump. The first one visually dimmed all the lights ~ as if the alternator had cut out. Afterwards, the cutouts/stumbling continued every time I hit a bump. It appeared to be the rear tires hitting that was causing the stumbling. In addition, the seatbelt warning light, and the coolant warning light flickered on and off; the coolant light flickered sometimes for as long as 10 minutes, before shutting off and restarting after another bump.

When I got down to Orange County, things quieted down. The OC freeways are much nicer, and I have never had this stumbling problem as I drive around here.

Yesterday, I had a no-start after several days of problem free driving. Since the neg cable was still happily connected, I checked the pos cable. It too wasn't clamped down, so I filed the inside of the terminal down to clean metal, replaced and tightened. The van started no problem, idled fine and drove home. It started fine after shutting down at home while still hot, and started fine this morning when cold.

When the van goes into the "no-start" mode, it has power; the battery and oil light come on, and the coolant light flickers then stops after a couple of seconds. I can hear a click, and nothing else. I checked, and have 12v at the pump, and both sides of the fuel relay. The pump does not run (at least I think it doesn't ~ that thing is impossible to hear now that I've cleaned it out...).

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Summary:

At freeway speeds, stumbles/loses power when rear wheels hit a bump
Coolant light/seat belt light flash intermittently; are not caused by normal failure/problem
Occasional no start with power to ECU and Fuel Pump; dash lights work correctly
Unhooking the battery *may* enable the engine to restart after 'no-start' occurs.

So what do these problems suggest?

The grounds in the engine bay are all good ~ they've been recently (a few months ago) checked, metal filed and wires/screws tightened.
The ECU is a used replacement
The alt is charging correctly when running (13.7v)

I'm wondering if my used ECU has a crack, or perhaps a short somewhere that only affects it when strongly bounced. I cannot recreate these experiences in OC; the roads are just too good here. I hit some RR tracks at 50mph Tuesday, and the engine didn't even pause, let alone stutter.

Ideas...?

Mike

[Amskeptic]

I'm wondering if my used ECU has a crack, or perhaps a short

Let's not get too catastrophic. ECU's are pretty sturdy stuff.

Wires can fail inside their shiny pretty vinyl sheaths where they chafe through even intact grommets. Your best bet to narrow it down is unfortunately going to be a failure. Remember that if it starts right up and drives nicely after you mess around with battery cables, it is not anything having to do with the engine. Sounds like you are right up at the very source of power, internal battery open circuits can occur from people who violently twist cables off, batteries can jerk at cables on bumps, starter solenoid terminal can get broken from over-tightening . . . . interesting, this.
Colin

[Lanval]

Well,

I'm not going to replace this ECU yet, but it's interesting that this problem only appeared now. I'll assume it's been there all along (the stuttering which suggests a short/bad ground to me) but unknown due to the quality of the roads hereabouts. On the way up I did 405/605/210 ~ all good, well-paved freeways. The 110 is horrific due to its age, and the 5 due to use. Both were a constant round of stuttering and flashing lights.

The 'no-start' I'm treating as a potentially separate issue that has emerged. It only seems to happen ( 2 times on Sunday, once on Wed) after driving for some time, so I'm not ruling out 'hot start syndrome' or something along those lines.

As you say, it's probably going to take a more substantial failure to get to the bottom of this, but I'll add a few things:

I looked at the starter motor; it's old and rusty ~ it's been 'ratted', so I'm wondering about the state of the wires to the starter. I'll be under the van, probably tomorrow, to check their state. The starter itself is probably original, and could be replaced I think.

The transmission to body ground is OE too, by the looks of it. At the least I'll clean those, and the ground points behind the dash.

Mike

[Amskeptic]

it's probably going to take a more substantial failure to get to the bottom of this,

Try to make the engine stall as it idles in the driveway by gently tapping and jerking wires that you feel may be involved. Heck, tap the ECU, you know, pull it out, start the engine, and give it the ol Pasadena Freeway expansion joint simulation.
Colin

[Lanval]

it's probably going to take a more substantial failure to get to the bottom of this,

Try to make the engine stall as it idles in the driveway by gently tapping and jerking wires that you feel may be involved. Heck, tap the ECU, you know, pull it out, start the engine, and give it the ol Pasadena Freeway expansion joint simulation.
Colin

This was my plan ~ it's the only way I can figure out to get a sense of where in the system things are going south.

Would you think the 'no start' and stumbling are separate issues? I'm thinking the coil or the starter motor may be at issue for the 'no start' problem...

[Amskeptic]

Would you think the 'no start' and stumbling are separate issues? I'm thinking the coil or the starter motor may be at issue for the 'no start' problem...

Now you KNOW I am not going to get involved with such rampant broad speculation. How does "coil" and "starter motor" get in the same sentence? Either the engine is cranking over and not firing (maybe ignition) or the engine is not turning over (starter).
Colin
(let's Samba-simulate: "hey everybody, I am the proud owner of a new to me! van its a 70 or 80 or something and I have a little problem with it chugging or not being smooth do I need a Webber or a external oil cooler?")

[Lanval]

Would you think the 'no start' and stumbling are separate issues? I'm thinking the coil or the starter motor may be at issue for the 'no start' problem...

Now you KNOW I am not going to get involved with such rampant broad speculation. How does "coil" and "starter motor" get in the same sentence? Either the engine is cranking over and not firing (maybe ignition) or the engine is not turning over (starter).
Colin
(let's Samba-simulate: "hey everybody, I am the proud owner of a new to me! van its a 70 or 80 or something and I have a little problem with it chugging or not being smooth do I need a Webber or a external oil cooler?")

Oh, you and your "methodical approach"... you probably don't believe that the stork brings babies either. Fine, I'll go read about the various pieces and educate myself, but I much prefer guessing it's "witches" in the dark with the other Cro-magnons.

Mike

Oh, and as for getting involved, by answering my question about the coil vs. starter you did get involved in "rampant speculation". Hah.

"When the hand's off duty, talk to the booty!"