Intermittent Low Power Part II

[ninetytwo]

As some of you may recall, last summer my 400E ran into low power/stumbling situations every now and then. I replaced the caps & rotors, which looked a bit dirty with condensation. Today about 1,000 miles later, its back and worse.

Same situation: 13 miles from home on the same hill, when I press for more power to climb it the engine suddenly has no power, stumbles, and can maintain 40MPH but really struggles to accelerate. Today it something else happened: it sounded like it had a "fart cannon" exhaust, had a terrible idle, and stalled immediately after being put into reverse after I pulled off the road for 20 minutes.

There was also what seemed like excessive heat and cooling noises from the exhaust system along with a nasty fuel smell. The caps & rotors look fine. The past 1,000 miles have been fine. This is the second time time in a week that its had this issue and like last year, the problem went away on the return trip home.

I need to plug in the laptop later tonight to see if there are codes but man this is annoying. I've read a few posts about clogged cats. Wouldn't a clogged cat always present a problem? or does the debris shift around to present as "ok" every now and then?

Aside from checking the rotors, what else might an amateur mechanic check?

 

[gsxr]

What you describe sounds VERY much like misfiring, i.e. secondary ignition problems. If so, there will be no fault codes. And, the problem may disappear either later the same day, or may disappear if the car is driven regularly (daily, or almost daily). If the car pulls strong to redline when it isn't misfiring, the cats are fine.

Questions:

1) You mentioned a laptop, do you have SDS with HHT-Win to view live data from the EZL? This will prove if it's an ignition problem, and also pinpoint the specific cylinders at fault.

2) Is the scenario a cold start, followed by a 13 mile drive on mostly level ground, then there's a hill where it misfires and has no power? This would fit perfectly with the secondary ignition faults.

3) What brand caps/rotors were installed, and were the insulators replaced at the same time? How old are the wires, coils, plugs, what brands, etc etc.

4) Were the cam oil seals inspected for leakage behind the insulator? The insulator must be removed to check this.

5) Have you added the additional venting slots to the new (1000-mile old) caps as described in @JC220's epic thread here? See posts 2 and 3.

6) Has the crank sensor (CKP) ever been replaced, at the flywheel behind the driver side cylinder head?

 

[nocfn]

You may want to check that your moisture is not oily. The cam seals harden with age and when they are replaced, along with the caps/rotors and you are certain that the wires are good too, then you can most likely rule out ignition components directly. Cam magnets can be sealed but they fail later (leak) so while you are there it is incremental to change them out. (armature change as well). As for the catalyst - perhaps GSXR will assert his prowess on the plugging.... in my view it is possible.

 

[nocfn]

Dave(GSXR) typed in before me lol you are in good hands.

 

[ninetytwo]

SDS reported no stored codes nor any faults while idling.

@gsxr Thank you for your detailed question. To reply:

1) Yes I do- I have the HHT emulator from Xentry. The only live data I’m able to capture right now is with the car idling in the garage. I’ll have to find help to capture it while driving. SDS reported no stored codes or faults while idling. Idle sounded normal this time, reported at 646rpm. When the car stalled in reverse it was much lower.

I’m curious to know how that pin-pointing might go? Will the HHT-Win identify a fault? Or will I need to look for something specific from the live data?

2) Yes, that is very much the scenario. The odd thing is how rarely it happens. Prior to this I’ve been in stop/go traffic in 92F weather, climbed steeper hills, and done a multi-stop errand trip, all flawlessly.

3) The shop installed Bosch. I can’t say with certainty if the insulators were replaced. For the sake of diagnosis, I’ll say no. The wires and plugs were replaced in 2018 with OEM parts. I made sure to have the shop buy the German-made Bosch plugs. That is roughly 12,000 miles ago.

The coils have not been changed under my ownership.

4) I have no checked them yet during this recent recurrence. I didn’t see any oily residue last year.

5) No, I haven’t added those venting slots. I read that thread last year and had hoped that this replacement would work but I should just buy the tools needed and try to modify this myself.

6) No, to the best of my knowledge the crank sensor has not been replaced.

@nocfn

Thank you for your reply, too.

The cam seals haven’t been replaced under my ownership. I have noticed more fuzzy oil grime under the front vanity cover than was there last year. Unfortunately my well regarded shop closed suddenly due to retirement. The next one with good word of mouth is farther away but I’ve got an appointment.

I really need to commit some of the procedures to memory and not be afraid to follow guides to take things apart.

The moisture didn’t seem oily but I don’t have a basis of comparison. It didn’t seem like 3 in 1 oil.

What is the armature changed you mentioned?

 

[gsxr]

SDS reported no stored codes nor any faults while idling.

I expected this... ignition problems rarely store fault codes unless the car is driven a long time with a persistent misfire. This is partly why it's difficult to diagnose.

1) Yes I do- I have the HHT emulator from Xentry. The only live data I’m able to capture right now is with the car idling in the garage. I’ll have to find help to capture it while driving. SDS reported no stored codes or faults while idling. Idle sounded normal this time, reported at 646rpm. When the car stalled in reverse it was much lower.

I’m curious to know how that pin-pointing might go? Will the HHT-Win identify a fault? Or will I need to look for something specific from the live data?

You view live data from EZL/DI while the misfire / power loss is occurring. Cylinders which intermittently show double normal voltage (65-70v instead of 30-35v) are misfiring. This will show you which cylinders are causing the problem. If the problem is occurring and all voltages remain normal, it may not be a misfire, but I doubt it. Note that idle RPM should be 650 in P/N and 500-550 in gear, but may be lower if misfiring.

2) Yes, that is very much the scenario. The odd thing is how rarely it happens. Prior to this I’ve been in stop/go traffic in 92F weather, climbed steeper hills, and done a multi-stop errand trip, all flawlessly.

It's often related to time after a cold start, along with time since the engine last reached operating temp. In prior scenarios (see posts years ago on the forum), another symptom was the car would perform flawlessly if driven frequently, but if parked for 2-3 weeks then it would misfire badly 10-20 minutes after the next cold start. In some cases, new caps/rotors AND insulators would cure the issue. In a humid climate, additional venting may be needed.

3) The shop installed Bosch. I can’t say with certainty if the insulators were replaced. For the sake of diagnosis, I’ll say no. The wires and plugs were replaced in 2018 with OEM parts. I made sure to have the shop buy the German-made Bosch plugs. That is roughly 12,000 miles ago.

Shops rarely replace the insulators. I'd pull the insulators and inspect the back side. If there is liquid present, this may be related to your problems, but at that point you'll need to replace the insulators / check the cam seals / etc etc. Lots of forum threads about the Liquid-Behind-Insulator syndrome.

The coils have not been changed under my ownership.

New coils would be nice preventive maintenance, but if the coils were bad, the car would likely run poorly all the time. I think the problem is elsewhere. Coils are a relatively rare failure.

4) I have no checked them yet during this recent recurrence. I didn’t see any oily residue last year.

If the cam seals show no trace of oil leakage you could leave them alone, but it wouldn't hurt to change proactively either. They are cheap and it's not a bad DIY job. If the insulators are dry, I doubt this is the root cause.

5) No, I haven’t added those venting slots. I read that thread last year and had hoped that this replacement would work but I should just buy the tools needed and try to modify this myself.

I'd add the slots ASAP. It's quick and easy. With Dremel you don't even have to remove the wires from the cap, just remove from the head and hold it with the wires attached.

6) No, to the best of my knowledge the crank sensor has not been replaced.

The CKP is a long shot but when flaky/intermittent, it can cause some seriously bizarre behavior, with no fault codes, and no way to diagnose (that I'm aware of) besides replacing with OE to see if there's any difference. I'd rule out ignition first. If the live data was showing normal ignition voltages on all cylinders while misfiring or losing power, then I'd try a new CKP.


Oh, and for whatever reason, it's the passenger side cap/rotor that usually causes the misfiring...

 

[nocfn]

I was right, Dave has you in good hands.

Since I replaced all of the ignition stuff, I also placed a piece of fiberglass insulation, maybe 4"x 6" outside the passenger side cap, tucked around it and then placed the black vanity cover over it. Now it may or may not help, but their may be something to the fan, airflow to the proximity to that side of the flow thru the grille/fan that produces an increase in condensate.

It may be that I am just all sorted so I do not have any other issues since the R/R of cam seals and all new bits relating to ignition.

I may have the same results wearing a tinfoil hat, standing on my left leg facing east. If not, that little swatch of bats insulation I pealed back from my shop's attic acts as my pacifier. YMMV

 

[gsxr]

@ninetytwo, any update on your low power problems?

 

[ninetytwo]

Oh no, I never wanted to be one of those members who abandon their threads. But here I am, I apologize.

My shop was able to fix the problem by the replacement method. Its tough in New England; the driving season is short, the vintage/classic cars are numerous, and the shops that people trust to work on them are always booking a month or more out. I'm not a proponent of throwing new parts at something, especially when there's a useful modification. Last year I was willing to throw money at it so I could drive the car a few more weeks before this region desalinates the oceans and deposits it on the roads.

I spoke with the shop today about helping me cut the rotor caps for the venting modification. We also replaced the seals, which the previous shop didn't do. So hopefully this will be a good season and the problem won't return. As always I appreciate everyone's help. Its great not feeling (or being) stranded with a problem on such a lovely car.