Jimmy Jones

Hello all, I recently purchased an early 85 944. When I test drove it there was no shaking at idle, and the car seemed to be idling fine around 1000 rpm.

Last night I started it up and the car is shaking very badly. Engine RPM gauge is showing that the engine RPM's are not even registering 100 (one hundred). Letting the car warm up does not seem to help. Temperature looks OK, letting it sit at idle for about 10 minutes and it did not get too hot. I took it for a quick drive and the shaking goes away between 1500 and 2000 RPM. Stopping it and letting it idle back down and sometimes it idles around 1000, with shake, and other times it would drop back down to a zero idle reading and shake pretty violently.

First thought was motor mounts, but I am wondering if there is a better path I can follow here, before doing the motor mounts.

Thanks in advance for the help, I am researching but it seems most of the shaking issues on the forum are at higher RPM...

Dougs951S

Something is definitely not right, a motor wont idle at 100 rpm (thats significantly less than cranking speed) so in all likely hood your tach is not working correctly and its losing signal for whatever reason. Your speed sensor may be shot. In any case, shaking can be caused by a few things, but if you are saying that is idles smoothly sometimes that basically eliminates it being the balance shafts out of phase. It sounds like the car has some pretty significant running issues (massive vacuum leak or an electrical hiccup) in addition to having possibly shot motor mounts. Any belt that is squealing obviously just needs to be tensioned. Does the car have A/C or power steering? What is the maintenance history like on this car? it sounds like it was neglected..

Jimmy Jones

I would say it was probably neglected. But the price was cheap enough for me to grab it and start working on it. The power steering belt has been removed, and I know that the ac is not working. The drive belt (serpentine belt) looks like it could us a replacement. My first thought was to grab new drive belts and get them on and tensioned correctly. The only thing I guess I am worried about is continuing to start up the car if it's a more serious issue that could damage the engine block itself.

I am fairly competent at simple mechanical jobs, but diagnosing issues like this is not a strong point for sure. Just trying to get feedback on a path to take.

Dougs951S

forget the squealing belt (which is more than likely your AC/alt belt, personally I'd just delete the A/C and gut the power steering) for now and figure out your much more pressing issue, you have a major electrical problem it sounds like. I'd start with replacing the timing and balance belts and changing the oil if it were my car, and then while you are in there take a look at the vacuum system. Chances are there are multiple leaks. Go from there.

By the way I hope you don't mind me asking but what did you pay for this car?

Jimmy Jones

OK awesome, that's what I was looking for. Thanks for the help.

I paid $2500. Probably too much (yeah I am starting to think I should not have bought it), but the body is in good shape and the interior looks better than any other I looked at.

Jimmy Jones

If I'm going to be doing the timing and balance belts, I am wondering if I should go ahead and replace the rollers while I am in there also?

Dougs951S

Its a good idea given that it sounds like your car was not well taken care of. Put a new water pump in it too, you'll be glad you did.

Jimmy Jones

Today I took it out and it was actually fine, just like before. The only difference between today and the last two days is temperature. It's in the 40's today and it was in the low 20's the last few days. When the tac was working, it's idling just under 800. The shaking was not bad at all today.

william_b_noble

temperature and humidity, maybe - I would absolutely change belt and rollers ASAP. Then change ignition wires, rotor and cap and plugs. Check for a sticky idle bypass valve (it lives under the intake manifold), and check for vac leaks. MAKE SURE the vac lines to the fuel pressure damper and regulator are connected. Change O2 sensor (they are about $30 if you use a generic replacement and not an OEM unit), and check the air flow sensor. check the J-tube for cracks.

Devia

I'd definitely check the vacuum lines, fuel pressure dampener & regulator. AFM is also not difficult to check. I had a fuel regulator go on the rail, sprayed gas over Legoland's shoulder, 6'. Wanted to take a pic, but it's one of those things: you just don't play with gas!

I had an issue where my car wasn't behaving: Speed & crank sensors! You can switch the two, see if it smooths the car out; they're identical. Just make sure that they're seated, before you put the bolts back in...you really wouldn't want to overhaul a transmission over dropping a bolt into one of the holes.

Anyway, regular maintenance, checking simple things are usually WHAT is needed with these cars, to start with. ALWAYS replace the rollers, tensionors every time you replace the timing belt/balance shaft belt. If you're in there, please, please change the waterpump & thermostat! You'll be so glad you did! CHECK the hoses, while you're at it. Are they mushy? Easy, cheap fix!

ALSO: change that oil, in the engine. AND the transaxle! That's overlooked so many times! THAT can cost you an expensive transaxle job.

Check the rotors, brake pads, repack the wheel bearings w/grease or replace them.

Every time you buy a car, unless you get FULL records of service, just best to have everything checked out, replaced. Make a new record, keep it on file for it. You don't want any belts breaking, then wonder why you're in the shop having a valve job done...

Devia

Jimmy: DO the motor mounts look toast?

Dougs951S

How in the world would you end up having to rebuild a tranny because of the speed/reference sensor bolts backing out??

Jimmy Jones

Motor mounts do look bad. It's on my list. New oil yesterday, the mechanic noticed the distributor cap was loose, he could not figure out how to get it on tight, so I did it when I got home, and it seems to be idling slightly better now once warmed up.

I took the car to a muffler shop today because I am getting an exhaust smell in the cabin. He checked and said there was no leaks, but there seems to be something missing next to the oxygen sensor, and exhaust is coming out of the hole. He plugged it with his finger and it was quite a difference in noise.



I am missing either part 21 cap, or part 24 emission tube and everything that goes with it... I'm not exactly sure what this is for but I am doing research now. Input is welcome!

Brakes and rotors are in good shape, suspension parts are in good shape, sounds like the wheel bearings on the rear could be done. I need an alignment too. And of course some oil leaks, nothing major yet but replacing those seals is on the list too.

Jfrahm

There is an exhaust sampling tube for factory diagnostic that goes there, some use a lug nut to cap it, or if the hex head is still there I think you can put a ball bearing in there to replace the tube. The tubes rust off and get tossed.

Dougs951S

yup, a factory aluminum lug will work just fine despite the temperature and pressure, thats what has been on mine for over 2 years.