i have searched for the past few hours and i'm wondering if the problems my new 83' 944 is exhibiting have a common cause.

-temp / gas gauge both work intermittently- gas is relatively reliable but the temp will hit max temp side at idle and goes down every time the car gets moving again (no red light at any point)
-heater not working at all, blows cold air. but peculiarly, with the blower heat will emanate from the vents, but very little
-engine vibrates the cabin violently at idle, but smooths out with throttle input. but the engine mounts seem fine as the engine itself does not buck under throttle
-hitting the dash will occasionally bob the temp needle
-the oil pressure gauge is also quite bouncy

i apologize for making you deal with another newbie, but please know that any input is absolute gold to me. thanks, i'm excited about having a relatively reliable dd!

 

check all the grounds on the car. they are notorious on 944s for causing electrical issues.

check your coolant system for air bubbles. also, your fans may not be coming on when they should be, which is why temp climbs while sitting but goes to normal when moving. the fan thermoswitch is on the radiator and is an easy part to replace.

your heater valve may be disconnected. it is located at the back of the engine bay, under the intake manifold and above the bellhousing. there should be some cables running to it, they may be unhooked or the valve is busted.

shaking at idle is almost certainly your motor mounts going bad. what is your idle speed set at? on an early car you can adjust idle speed by taking a flat-blade screwdriver and an 8mm wrench to the throttle body and adjusting the throttle stop screw.

 

If idle is the only time it vibrates, it's probably the motor mounts.

I've seen that same temp gauge problem on my 944 and others. If your problem is like mine, it's the gauge, and every time it happens I smack the dash and the needle shifts back. One of these days I will open up the gauge and resolder all the solder joints, hopefully that will help.

It also sounds like you have air in the coolant system though. The coolant system on 944s does not self-bleed. The bleeder screw is a 12mm bolt on the top of the water pipe coming from the front of the engine. This pipe connects to the upper radiator hose. Fill up the coolant tank, warm up the car to operating temp (so the thermostat opens), open the bolt and wait for water to squirt out. Revving helps. Close the bolt while water is squirting out. Don't over-tighten this bolt, it always looks to me like it's just waiting to either get stripped out or snap.

 

i will try the bleed process tomorrow, along with some coolant and distilled water. is there a common preference amongst the 944'ers? idle sits around 900-1100, depending on how it's feeling. the temp gauge and gas gauge both seem slightly sketchy.

well the temp gauge does seem to have some kind of consistency... if i hit the dash it might readjust it, but sitting in traffic the only thing i've done is mess with the hvac, which arbitrarily eases the needle down to 3/4ths

also, i hear a slight grinding noise when i downshift... clutch (rubber seal) going out?

i would like to thank you both for the time yall took to help specifically diagnose my situation. best welcome i've received thusfar on a new project. i would also like to ask... the engine mounts alone can cause this much vibration in the cabin? what characteristic of the engine mounts enable less vibration when you gas the car, as opposed to idle? centrifugal nature of the engine? it doesn't seem to buck visually at all from the engine bay

nice, thanks for the tips.

 

That should be "gone bad". Both of them I would think, if the cabin is "shaking violently at idle".

This should be fixed ASAP -- it is well documented that bad things can result from all that vibration (oil pickup tubes breaking, etc.) As well as it being no fun, of course.

BTW, I've never heard of "bucking under acceleration" as a symptom of bad engine mounts, at least not on these cars. The main clue is the vibration smoothing out as engine RPM increases, as observed.

 

I have an aftermarket gauge cluster showing temp, oil, and voltage, but I wondered about the stock temp gauge not working, or was it unhooked. I found it was hooked up, but badly corroded. I cleaned it, and it started working again. I have two temp guages now. (Other guage is separately wired from another source.)

The oilpressure guage (stock) seems to bounce when I come to a stoplight. Normal cruising it sits near the top of the guage. There seems to be a slight delay which causes the needle to bounce around. It appears to be normal from what I have read.

violent shaking at idle could be motor mounts. I would just increase the idle slightly (to keep it from vibrating), and worry about the mounts once you get these other items worked out. Mine seems to like 1050-1100rpm. Any lower, and mine will vibrate just enough to make it annoying.

 

Bad advice, IMHO.

 

I agree that new motor mounts should be high on your 'to do' list. Another high priority item is the cam and balance shaft belts (if you have no history on when they were last replaced). A broken T-belt will almost guarantee bent valves, etc. so you don't want to ignore this maintenance item. As for grinding noise on downshift, I'd try bleeding the clutch hydraulics (and looking for leaks). You can find a lot of good information here on 'how-to':
http://clarks-garage.com/

 

is this symptomatically mutually exclusive of other underlying causes? doing engine mounts does not sound fun

also, why do you think higher idle to compensate for the vibration is a bad idea? haha aside from the obvious, which is that i'm not actually solving the problem

 

what did you use to clean? temp gauge seems to be functioning in the sense that when the car is cold, it will be to the far left, and with air flow, the meter stays almost dead center. it is just that in traffic the temp will swing all the way right and the car sounds incredibly unhappy. and agreed, 1100 seems to be where the idle seems most comfortable. <1k is an unhappy place. when sitting in traffic actually the car will surge idle to about 1000-1100, but only occasionally.

you guys reckon there's some correlation between the idle surge and the way the needle dips below standard idle for a brief period? or that's attributable to the inferior DME's of earlier year 944s, as i've heard mention.

 

It's not a bad a job as some people say. It is a bit tricky, meaning it's a lot easier if you know a few tricks. At least that was my experience. I really didn't think it was a difficult job at all.

Even if this lessens the problem, the engine will still be subject to more potentially damaging vibration than if it was fixed. If the engine is vibrating as badly as you say, I wouldn't mess around. Sounds like this is long overdue, actually.

 

i haven't seen any leaks thus far, but replacing fluids sounds like an optimistic and economical start to diagnosing the problem. as for the t-belt... all these silly porsche exclusive tools required are quite daunting to get me started! the car itself seems to run very strong, and the car allegedly has an aftermarket exhaust manifold and muffler, which i cannot confirm because they look to be OEM and old as dirt. i'll take pics when i can.

seems like the first thing i should do is flush, fill, and bleed? my cooling system.

is there any way to visually identify t-belt deterioration?

 

Unfortunately no. They can be well past their replacement time and still look as good as new (which is a potential trap for the unwary, obviously ).

 

While not the proper way to do it, it was also mentioned the timing belts should be changed, as well as a host of other things, if this is someones first Porsche and they are not mechanically inclined, or have the proper tools/place to work safely, these can be a huge undertaking. When considering someone may have paid less than $4K, these expenses can effectively increase the cost of the car by 50% or more. Not to mention risking doing it wrong, simply breaking things accidentally while working on them, or finding out more that needs to be replaced once you get into a task. (while your at it syndrome)

I am looking at this as triage. Fixing a motor mount only to have the car overheat the next day is not the best way to maintain a car demonstrating multiple symptoms. Look after the small things yourself, and for larger jobs, take it to someone you trust to fix it properly.

To the original poster, clean any/all wire connectors using some contact cleaner (spray) and some 400-600 grit sandpaper to make it all shiny bare metal again. Some dilectric grease to seal the connections from moisture will help protect it after it is cleaned up.

Good luck!

 

Hey mala..... well you know who you are! LOL! I just bought my first in October. A red 84 that I now love. That has not alway been true. I came very near to pulling it out of the shop and setting it on fire. That is not an exaggeration. Welcome to Rennlist and 944 ownership. I followed the help and advice of these guys and they did me right. I will do my best to return the favor. Ask a lot of questions and read the Clarks Garage page.

I haven't had the same electrical problems as you have now. However the rattle is most certainly the mounts. Replace them! It is running and you have already started on the project. The job is not something I want to do again but it is so very nice when they are done! Other than the clutch it is the one thing I did that transformed the car from junker to sports car. Mine rattled so bad that it made it hard to diagnose anything else.

Since October I've replaced or repaired:

Engine mounts
DME
Speed and reference sensors....twice
Clutch-includes everything associated
Clutch master and slave cylinders
All wheel bearings and seals
Both axle shafts
Various bulbs, about a dozen I think
Both tie rods
Brakes- rotors, lines, pads, calipers, fluid
Steering wheel
Speakers
Arm Rest-center
Battery cables and grounds
Windshield wipers
Battery
Water drains
Heater valve
Arm rests-doors
Seat runners
E-brake handle/system
Hood and hatch props
Exhaust system
Locks, latches and hinges
Tune-up and fluid changes throughout
Struts and shocks
Shifter and linkages

Jesus that's depressing when I see it typed out here! And I still have a list almost as long to do yet! Nevertheless, I have less than $3,000 in it, I have some new tools and it is now an amazing little car to drive. Good luck and we're here to help!