bureau13

Since this issue has had some discussion in my other thread about "poor running sometimes" I'll recap briefly here. Also...I'm pretty baffled as to where to look from here. Which is annoying since it's otherwise running really well now.

The symptom is that, every so often, the car just shuts down what I believe to be the ignition circuit. It acts like I turn it off with the key, but then immediately turn it back on so all the gauge lights are on. If the car is idling, the motor just stops. Radio continues, dash is lit up, etc. If the car is moving, there's a "hesitation," sometimes subtle sometimes fairly harsh, and it feels like I've pushed the break momentarily, then I get a big tach bounce and the car keeps going. I believe it's in effect being push-started by the car's own motion while in gear.

Sometimes it happens a lot, sometimes almost never. I tried a new ignition switch, but it didn't fix it. I put in new Bosch 53B-type relays for the fuel pump, X-bus, LH and EZF, no change. I replaced the ignition amps and CPS and cleaned up the grounds in the V to address a different problem but it was after this problem started, and it obviously did not fix it.

I've noticed sometimes it has to crank a while before it starts, but I suppose that could be the problem happening during that period. Also, during a test drive yesterday, it happened while moving 2 or 3 times in about ten seconds and I smelled a bit of "burning electronics" smell, but not super strong and I can't even say for sure it was coming from my car. But barring any better suggestions to try first I will pull the CE panel and see if I can find anything on the back that looks like it might be getting overly hot.

I've also tried to trigger the problem by push, pulling and squeezing various things like the ignition switch harness, the CE panel as well as individual relays, CPS harness, ground wires, battery ground cable, ignition wires, pretty much anything I could think of, and nothing is reliably triggering it.

I'm at a bit of a loss here, so any questions or additional tests to try would be helpful!

belgiumbarry

as far i understand you may have searched it "electrical" ....but fuel pump ? either pump or 12V feed to it , wiring ,fuse ???

i'm biased, first rally i had a bad fuel pump fuse contact , could solve that , second rally bad pump and game over.
With 12 amps it stays a heavy consumer onboard ... on my CIS car. Don't know with LH .... perhaps a bit less i assume.

Adamant1971

My 87 was doing all kinds of strange things recently. Shutting down while driving, failing to start, tach going totally mental etc,

Turned out the ground strap terminal in the hatch was not making a good connection. a simple cleaning was all it needed.

Worth a shot to check to clean your ground strap connections and other grounds. I had done what you did by wiggling wires etc with no luck, until I undid the ground strap while it was acting up, as soon as I loosened the fly nut the car came back to life.

dr bob

I know you've been wrestling on this for a while. But sometimes a back-to-basics look is warranted. To that end, revisit the connections at the battery. As Adam shares, the ground strap is a known intermittent and not at all obvious failure point. If yours is original, even if it looks OK, replace it. I chased electrical gremlins, ultimately solved with a new heavy-duty ground strap. Original looked fine but there was enough hidden corrosion to prevent full-time full function. At the other end of the battery, there are auxiliary connections for fuel pump, injection and ignition power. On S4+ cars, add the cooling fans power. Those are the smaller red wires connected to the pinch bolt in the battery positive clamp. The individual ring terminals need to be clean and bright, as does the bolts and nut. These connections seem to get erratic especially when the battery isn't correctly clamped down. Anyway, clean and bright with a brass detailer's toothbrush, snug on the nut, plus clean battery posts and clamps. Normal annual maintenance stuff, but sometimes a new look will help find new problems.

Look at teh wiring to the oxy sensor in the CE panel area. The heater shares power from one of those smaller battery wires. Make sure there's nothing shorting to ground in the cabin, through the grommet in the tunnel, and by the eat shields above the exhaust crossover at the sensor itself.

bureau13

Good stuff guys, thank you. I will do those things. It's funny, shortly after I bought the car (5+ years ago or so) I had an intermittent issue where the car would just die (no restarting itself though) and then wouldn't start until some random time later. It was that fuel pump connection at the battery. I guess this symptom seems different so I wasn't thinking that could be it, but all that stuff is pretty easy to check, clean up, etc, and it makes sense to check it.

I've also noticed some water in the back part of the hatch after a strong rain, that could hasten any corrosion I would think. I think that's a bad hatch seal, I have the rubber part but I haven't put it in yet.

Petza914

How new and well connected is the green wire?

dr bob

I think this is for his 86.5, with EZF triggering from a crank position sensor. So no green wire.

But your question does bring us to the related question of the condition of the CPS, its wiring and connections.

Petza914

Clues from the first post should have led me to see it wasn't old enough to have a green wire, but cps definitely a possible issue, especially with the description of what the tach does during a stall event.

bureau13

So the CPS is brand new...I replaced that in the other thread. The connector on the other end seems OK, but the boot did have a slight tear in it. I couldn't see that any bare wiring was exposed, but it was a small tear so I couldn't really see down inside very well. I did patch up the whole with some liquid electrical tape. I would imagine that's a painful job, replacing that? If I'm soldering wires in that location I would say there's a good chance I introduce problems, so I would want to rule everything else out first, I think. Is there a good place to monitor the CPS signal while the car runs? I'd have to beg, borrow or steal (OK I guess I could buy one) an o-scope, but if this seems likely, it's an option. About the tach needle behavior, however, I assumed it was just acting like when you crank the starter? But maybe that doesn't make sense.

I cleaned up and inspected the connections at the battery terminals. They looked fine, for what it's worth. I found my ground strap could be moved around a bit so I snugged them down a bit more. No more movement, but the problem is still there. Speaking of tach needle behavior, I did notice several small "dips" in idle, not in any sort of pattern, and one fairly large one, where it caught itself and the tach jumped back up, which was the first time I've seen it do that, unless those small dips are also related. Frankly, it's always kinda done that though. Also, when it dips, I detected a subtle flicker in the hazard light, which was on due to the parking break.

I have no idea if these minor observations are actual clues, or just me being paranoid and tying things together that shouldn't be.

I can look at the fuel pump feed perhaps, but if something else is the trigger, the fuel pump gets shut off anyway, right? Not sure exactly how that works though.

gazfish

Have your LH and EZF ECU’s ever been rebuilt. If they are original it might be time for a refresh?

Mrmerlin

did you use a Bosch CPS or the less expensive version?

dr bob

The CPS is related to lots of the symptoms you mention. When the engine threatens to stall, does the tach go to zero or just fall with the RPM drop. If the former, CPS is a suspect. The CPS via the tach signal sent to the injection controller is one thing that tells the fuel pump to run.

How is the rest of the top of engine wiring? Did you clean and secure the injection system ground point at the top rear by the CPS? Then on to the injection wiring, where a fault (short) in any injector's wiring will cause all to stop working. If the wiring for any of those is similar to what you report for your CPS connector, you may decide to get new connectors for all (injectors and CPS) and have a soldering-iron festival event under the hood. I think Roger stocks all the correct connector shells and pins. Do the throttle switch connector and look hard at the MAF connector at the same time; all live in the same environment and any could cause the erratic symptoms you describe.

How are the plug wires? Those usually show up as a rough idle and miss under load. Coil wire plugged in completely? You can use an Ohm meter to check the wires for open, but checking for "leaks" to ground takes a little more work. Easy first test is with a spray bottle and tap water, fogging the water over a running engine in the dark. Little lightning flashes tell you where spark energy is leaking to ground. I have a vintage CRT oscilloscope dedicated to automotive diagnosis. I think it still works... Anyway, it's handy to finding ignition issues, with just a little bit of creative connecting and probing. Replacing every ignition piece is cheaper than buying a decent 'scope though. Borrow one or find one used if you can rather than buy new.

The Forgotten On

How old is your temp II sensor? It should be replaced with every timing belt as when they fail they can cause all kinds of issues.

The battery terminals being loose as mentioned above is what caused my issues on my 89. Check those too as they're easy to get at.

Landseer

Valley ground wire corrosion on entry to ring terminals must be questioned then. Even the pattern of intermittancy is intermittent when these biotches fail. But it includes the range of symptoms described.

Due to being completely surrounded by fuel related components, the clip and resolder process for these has one hell of a pucker factor.

Solved the stall / no start /stutter / water in gas symptoms definitively on two cars for me.

Actually three counting the 84 euro. But that set of LH jetronic wires grounded to the cam cover instead of valley. Same thing solved it.

I'm in the east. My stuff is 35 years old and gets rained on. West guys don't necessarily have this concern.

dr bob

Unless fuel is leaking, soldering connector pins in the area has a zero pucker factor. There's always a fire extinguisher handy in the workbay, but no excess risk there vs. on the floor in thee passenger footwell doing other recovery fixes with the soldering iron and heatshrink with the butane torch.