Late model Carrera engine lugging

[LeckerNeunelf]

I washed the car last night ('89 Carrera), dried it off as good as I could, then did my usual, which is to drive it with as much spirit as the law will allow for a 5-8 mile trip. I figure warming the engine through and blowing some residual water out of the cracks after a wash is a good idea.

I happened to get stuck behind an annoyingly slow drivers. I'm not sure why, but I allowed the car lug a little while in 5th gear at 42-45 mph. The tach was below 2k but over 1.5k.

The reason I'm posting is because, the engine shuddered and spluttered in a way that I had not experienced before. It was quite annoyed at me. I downshifted to fourth. The revs picked up but some gurgle-surges continued, but much less. I built the revs up a little and everything smoothed out.

Then I gave the car a solid run through the gears; red lined it a couple of times. She seemed as happy as a clam in mud.

Question: Am I just a dork for lugging the engine, and this is normal? I've lugged engines before and they just seem to grumble a little before things correct. This was slightly more dramatic.

Is this perhaps a sign that the clutch is about to go?

I bought some transmission fluid (Mobile One Delvac) some months ago, with the idea of getting some clean stuff in there. I have not had a chance to do it yet. Does this factor?

Your thoughts appreciated.

[Hnichols]

I don't know, but I doubt it has anything to do with the clutch. Hopefully someone will chime in with some good ideas.

You weren't following that stupid "shift up" light, were you? If you go past 2K it tells you to shift up.

[stlrj]

Originally Posted by LeckerNeunelf

I happened to get stuck behind an annoyingly slow drivers. I'm not sure why, but I allowed the car lug a little while in 5th gear at 42-45 mph. The tach was below 2k but over 1.5k.

That's not lugging an engine. But adding throttle at that speed would be considered lugging.

The problem was when you washed the car the night before and got the ignition cables/distributor cap wet, they never got dry. Beru ignition cables are notorious for acting up when you get them wet. It has nothing to do with lugging.

Cheers,

Joe

[stlrj]

Originally Posted by Hnichols

You weren't following that stupid "shift up" light, were you? If you go past 2K it tells you to shift up.

That stupid "shift up" light is there to keep us graying adolescents from looking stupid with our engines all rev'd up like we had a bad tranny on the way to AMCO.


Cheers,

Joe

[twistoffat]

+1 on moisture in the dizzy. Dirty fuel will also give the same symptoms. Had you let the tank possibly run low and then refuelled?

[GH85Carrera]

Moisture in the distributor is one possibility for sure.

I had the strange issue of my 911 not running quite right after washing it for a while. I chased a lot of possibilities. The problem was solved when I replaced a bad fuel injector. If there was any moisture on the electrical connection it would go wonky until it was hot enough to evaporate the water. Then it was fine. I just replaced that one injector and all was well.

I even had all 6 injectors tested at a local shop. They all tested fine, but they obviously don't do it with a wet connection. I should have kept that injector but I had great joy in smashing it with a hammer.

[Drisump]

I personally never use 5th at under, say 55mph. I find that even routinely driving in a spirited manner, quite a bit of city driving (in my car at least) creates a situation where the car has difficulty in idling when cold, and it develops a mid RPM miss. At that point I usually add some Techron to the fuel and take her for an "Italian tune up"....this invariably solves the issues. My car at least, doesn't seem to thrive when driven at low RPM. I usually use 94 Chevron (available here) which contains no ethanol. From your description I wouldn't be concerned with the clutch or tranny, either the fuel or the spark were temporarily "acting up"...and was said before, probably a little water inside the cap.

[scarceller]

Open the dizzy and dry it out real good, it could still have moisture in it.

Why this mis-firing happens:
When you increase load on the engine cyl pressures go way up and the ability for spark to jump the spark plug gap gets harder, as this happens the spark tries to find the easiest path to ground and at light loads cyl pressures are low so that easy path is at the plug gap but as the pressures increase the easy path becomes the moisture in the dizzy and it follows the wet path to the dizzy's grounded metal body. And/or it also can find a wet path along the wires.

At very low RPMs like 40MPH in 5th gear at 2000RPMs it does not take much to increase load, simply tipping in on the Throttle sends cyl pressures way up!

One more thing I've learned:
The engine fan needs to spin and spin fast if ambient temps are above 80F! I monitor a lot of signals in my 3.2L with my laptop setup and you'd be amazed how CylHeadTemps rise at less than 3000RPMs. On a 90F day my CHTs are in the 170C range if RPMs are above 3000RPMs but take those RPMs down to <2500RPMs and very very quickly CHTs rise to 190C range! Bottom line is if it's hot out don't run these cars below 3000RPMs! You really need that engine fan moving a lot of air to keep the CHTs down.

[Dave Colangelo]

I usually do a spark plugs/air filter/oil change/dizzy cap and rotor change once or twice a season and often when this starts happening. It has never failed to smooth out my engine time and time again. On one occasion my plug wires were just old but a fresh set along with the mid season change helped everything quite nicely. I consider these high cycle parts (not that everything else isnt) but these tend to wear faster than other parts. Try doing the change on these things and see if it helps, wont run you more than $75.


Regards
Dave

[LeckerNeunelf]

Great info. Now that I think about it, I think I noticed this one other time (to a lesser extent), after washing the car. So, moisture is the likely culprit. Also, I've only owned the car for a couple of years. I have not changed the plugs, plug wires, distributor cap and rotor, etc. (dizzy?) in my time with it. I'll be on that soon. That said, twice annually seems OCD. In any case, the moisture theory make perfect sense.

Which prompts a question: I don't wash my car obsessively, but I wash it once a month (at least). It's a driveway job with a garden hose and P21s products for the most part. Be that as it may, it has always bothered me that inevitably rinse water goes through the whale tail grill into the engine bay. Most of it probably hits the air conditioning condenser and rolls toward the back. But a fair amount must end up on the engine around the, ahem, dizzy. It might drip onto the top too, near the MAF, etc.. As mentioned by others -- not good. So, how should I wash? Do people cover the grill on the whale-tail to keep water out? What about non-whale-tail set-ups?

Side note to scarceller -- I have a nice little hill that's exactly one mile from my house, it leads to a short flat, then a left turn through a light, followed by a right, then a left into my driveway, which is flat and leads to my garage. Throwing it into neutral at the top of the hill, if my timing is good on the light, I have just enough gravity power to coast all the way into my garage. Don't laugh! It's a lot of fun trying to make it. Be that as it may, I noticed my engine temp gauge actually ticks up a hair on this little coasting section. It certainly does not go down. I would have assumed that the engine would cool on a 60 second coast down a hill, but it seems to increase. I think this lends credence to your observation that RPMs should be high on a hot days.

A comment to stlrj: As a matter of fact, while I was not exactly following that stupid yellow shift light at the time, I was "influenced" by its hyperactive tendency to want me to shift up no matter how slow I'm driving. It made me think my German father taught me how to drive all wrong: "Shivft ven de motohr iz verking too high, like zo", then he runs our red Beetle up through every gear and back down before reaching the stop sign at the end of the empty parking lot. Cool but stressful. This is basically how I have been driving ever since. That is until I encountered the weird yellow light. My only saving grace it that it does not always work. I seems to go on long vacations, then mysteriously comes back to life only to show me that I'm shifting all wrong. Ha, ha. So, I have recently been trying to shift up more frequently and leave it in fifth for longer periods of time as a result of this "feature."

[scarceller]

That shift light is controlled by the Injector Timing pulse width (IPW), the tach actually gets it's signal for that light directly from the inj pulse width it then combines that IPW with RPM to determine when it lights. In other DME model cars the IPW signal is used for a fuel economy gauge, Mercedes and BMW had these in the 1980s. But in the 911 they used it to drive that fancy light.

[Steve W]

Check the condition of your cap and rotor, specifically for grooving on the rotor contacts. Grooving and/or excess wear causes the car to stumble badly when moisture is present because spark has an easier time flowing along moisture to ground, than bridging a 1mm gap.

[911pcars]

Originally Posted by scarceller

Open the dizzy and dry it out real good, it could still have moisture in it.

Why this mis-firing happens:
When you increase load on the engine cyl pressures go way up and the ability for spark to jump the spark plug gap gets harder, as this happens the spark tries to find the easiest path to ground and at light loads cyl pressures are low so that easy path is at the plug gap but as the pressures increase the easy path becomes the moisture in the dizzy and it follows the wet path to the dizzy's grounded metal body. And/or it also can find a wet path along the wires.

At very low RPMs like 40MPH in 5th gear at 2000RPMs it does not take much to increase load, simply tipping in on the Throttle sends cyl pressures way up!

One more thing I've learned:
The engine fan needs to spin and spin fast if ambient temps are above 80F! I monitor a lot of signals in my 3.2L with my laptop setup and you'd be amazed how CylHeadTemps rise at less than 3000RPMs. On a 90F day my CHTs are in the 170C range if RPMs are above 3000RPMs but take those RPMs down to <2500RPMs and very very quickly CHTs rise to 190C range! Bottom line is if it's hot out don't run these cars below 3000RPMs! You really need that engine fan moving a lot of air to keep the CHTs down.

+1

The symptom the OP experienced is feedback that a load is being applied to the engine (power demand) at low rpm, commensurate with wider-than-normal throttle opening below a threshold rpm. This is not to say that changing rotors, dist. caps, spark plugs and wires on an annual basis is the proper solution.

Merely cruising at "low rpms" is not necessarily lugging if the throttle is closed or just about (if you must,) but it's better practice to keep engine speed/throttle opening away from the lugging range. OTOH, keeping engine speed above 4000 rpm is also unnecessary for normal cruising unless you prefer a more aggressive driving style. In lesser cars, it's called the small penis syndrome. After all, there is a time and a place for everything. YMMV.

Sherwood

[kojo911]

Before you start buying parts I would suggest you buy a couple of bottles of fuel injector cleaner. I've had really good results with Red Line, others on the board have had good results with BG44 (?). Most people time the use of cleaners so that it occurs just before an oil change. The thought is that any of the cleaner that makes it's way to the oil will be disposed of. I typically put a full bottle of cleaner (enough to treat 20 gallons) into about 5 gallons or 1/4 above empty on my fuel gauge, then drive the car pretty hard. I use the second bottle in a full tank, burn that off, then change the oil. My '87 would lug/hesitate, or not take throttle smoothly at low RPM. This seemed to cure it. Even if this isn't the problem, it's probably been a while since the injectors have had any attention.

[scarceller]

I like to think of lugging as a condition that produces very hi Injector Pulse Width times with very little acceleration. Like doing 30MPH in 5th gear and going WOT. Here the IPW goes sky high and engine load goes to 100% instantly but not much happens acceleration wise. Couple this with the fact that the engine is not in it's peak torque band and you quickly generate a ton of heat into the surrounding cyl components. At this same time you are at WOT in low RPMs you have very reduced engine cooling air because of low RPM speeds. These motors don't do well under these conditions.

[Dave Colangelo]

Originally Posted by LeckerNeunelf

Great info. Now that I think about it, I think I noticed this one other time (to a lesser extent), after washing the car. So, moisture is the likely culprit. Also, I've only owned the car for a couple of years. I have not changed the plugs, plug wires, distributor cap and rotor, etc. (dizzy?) in my time with it. I'll be on that soon. That said, twice annually seems OCD. In any case, the moisture theory make perfect sense.

Which prompts a question: I don't wash my car obsessively, but I wash it once a month (at least). It's a driveway job with a garden hose and P21s products for the most part. Be that as it may, it has always bothered me that inevitably rinse water goes through the whale tail grill into the engine bay. Most of it probably hits the air conditioning condenser and rolls toward the back. But a fair amount must end up on the engine around the, ahem, dizzy. It might drip onto the top too, near the MAF, etc.. As mentioned by others -- not good. So, how should I wash? Do people cover the grill on the whale-tail to keep water out? What about non-whale-tail set-ups?

Side note to scarceller -- I have a nice little hill that's exactly one mile from my house, it leads to a short flat, then a left turn through a light, followed by a right, then a left into my driveway, which is flat and leads to my garage. Throwing it into neutral at the top of the hill, if my timing is good on the light, I have just enough gravity power to coast all the way into my garage. Don't laugh! It's a lot of fun trying to make it. Be that as it may, I noticed my engine temp gauge actually ticks up a hair on this little coasting section. It certainly does not go down. I would have assumed that the engine would cool on a 60 second coast down a hill, but it seems to increase. I think this lends credence to your observation that RPMs should be high on a hot days.

A comment to stlrj: As a matter of fact, while I was not exactly following that stupid yellow shift light at the time, I was "influenced" by its hyperactive tendency to want me to shift up no matter how slow I'm driving. It made me think my German father taught me how to drive all wrong: "Shivft ven de motohr iz verking too high, like zo", then he runs our red Beetle up through every gear and back down before reaching the stop sign at the end of the empty parking lot. Cool but stressful. This is basically how I have been driving ever since. That is until I encountered the weird yellow light. My only saving grace it that it does not always work. I seems to go on long vacations, then mysteriously comes back to life only to show me that I'm shifting all wrong. Ha, ha. So, I have recently been trying to shift up more frequently and leave it in fifth for longer periods of time as a result of this "feature."

I will admit twice annually is a bit much however the car is my DD and I drive it (at least to some extent) through the winter so its more about miles than time for me. Now that Im in a city I drive it less so I predict that time interval will get bigger and I dont always do everything at the same time. Oil filter is done every other change. Plugs in and around 6K or less if Im in there. Air filter, when it looks like its getting dirty. and dizzy cap and rotor if there is bucking or a lot of carbon build up on them.

Regards
Dave

[stlrj]

Originally Posted by LeckerNeunelf

It seems to go on long vacations, then mysteriously comes back to life only to show me that I'm shifting all wrong. Ha, ha. So, I have recently been trying to shift up more frequently and leave it in fifth for longer periods of time as a result of this "feature."

Again, that stupid "upshift light" is there to keep you from doing something stupid so you don't look stupid running with your engine all reved up for no good reason. Shifting when the light comes on will not result in lugging.

[LeckerNeunelf]

Yeah, I'm pretty sure "engine lugging" was the wrong thing for me to say. Although, allowing the RPMs to drop while in 5th, with moisture infecting the distributor cap/rotor (also perhaps the plug wires) from the preceding car wash, must have caused poor performance for a moment that felt sort of like "lugging". The car was running perfectly immediately before, and after I gave it more vroom.

I would like to thank everyone who replied. I just placed an order for some electrical tune up parts from our host. I will also soon be changing the tranny fluid. I've been meaning to do that for a while; and, I plan on running some fuel injection + valve cleaner. Not so much as a direct cure for this issue, but because I probably should have done this 3 months ago.

As for the "yellow up-shift light" not causing lugging --fully true. But it does seem to demand upshifts on the soon side. I'm sure it's doing some calculation that favors fuel economy. But it made me conscious of the idea that I should consider upshifting more frequently. Bear in mind, my yellow light only comes on from time to time, and it was not operational at the time.

[69-912-swt]

Sounds like your not getting the motor up to a good operating temp. I always try to run my 87 Carrera at least 15min every time she gets run !! And I live in Central Florida where it's always warm to HOT year round. It takes that long to get 12qts of oil up to operating temp. A few red line shifts seems to make her run better and idle smother.

I just back from the "Tail of the Dragon' and other NC mtn roads where it seemed like 2nd gear was best. Rpms from 2.5k to 5.5 for the curves and short straights was a blast with the Targa top off. Was a good exercise for my car !!

"Drive it like you STOLE IT"