Dan Brock

Hey guys,

I just did the timing belt maintenance on my 928 GT - was my first time ever doing any kind of mechanical work on a car, but I got it all back in one piece and it starts up so I'm happy with that. It was actually a lot of fun!

However, I noticed it's idling at around 500RPM... and that it will stall out at idle if I don't let it warm up for a good 15 minutes.

Is this common?

Also, would it be possible for the car to start up and run with only 7 out of 8 pistons activated?

I think I'm just being paranoid, but I feel like the engine is running a bit different after checking my timing belt. I'm hearing a strange sliding sound that goes along with the normal gurgle of the car. Keep in mind it's been in the garage for about 9 months so maybe it just needs to stretch it's legs?

Thanks dudes!
Dan

James Bailey

NOPE

Kiln_Red

Set the #1 piston to 0°TDC. Remove the TB covers. Expose the belt and cam gears. Photograph the alignment of each cam gear and post the pictures here. If the car ran fine before, then I bet the belt is off by a couple teeth.

17prospective buyer

Deffinitely seems like cam timing is off, retarded i guess?

Dan Brock

Thanks guys.

So it occurred to me that I probably didn't do the timing belt procedure correctly as I realized I only checked the tension on the passenger side timing belt and didn't check the right drivers side timing belt.

Do I need to do the timing belt check procedure on both sides?

Lastly, I forgot to check the tensions at 0' TDC. I just kind of checked it where it sat lol!

How exactly do I measure TDC? Do I need to jack the back wheels up so the engine will crank, or can I just put the car in neutral? How exactly do I tell if TDC is at 0'?

Thanks for the help dudes, and sorry for all the questions I am completely new to this!

Dan

Kiln_Red

Leave it in park if you want. Rear tires can sit on the ground. Just turn the crank over to 0°TDC. Tension is important, but make sure that the belt is on correctly. Your cam gears have to be positioned correctly before slipping on the belt.

Dan Brock

Thanks Kiln-Red

I'm actually only trying to check/adjust the timing belt.

I had a new one put on a year ago, however the former owner told me it was important to check timing belt tension once a year.

How exactly do you turn the crank/what part on the engine is the actual crank?

Do I need to take something off the engine in order to kill the compression inside in order to turn it? Like a spark plug or two?

Thanks ugys!
Dan

Dan Brock

Also, I noticed on the left hand side, underneath the left-side timing belt cover there is a pully that appears to be missing a belt. Here is the image of the belt that I think is missing and and arrow pointing to the component.



Any ideas what this component is for/is it crucial?

Rob Edwards

Hi Dan-

What year GT? 89, 90, or 91? Sounds like your issue might be timing related but the model year might become important if it's not timing.

You can leave it in neutral (with the parking brake on....). There's a 27 mm bolt buried in the center of the pulley on the nose of the crankshft. You need a 1/2"-drive breaker bar or long ratchet with a 3" extension. Then you need to turn the crankshaft (clockwise only! Clockwise when you're standing in front of the car, looking at the engine) to TDC, where cylinder #1 is at TDC. Since the passenger side distributor cap will be off in order to measure belt tension, you can make sure you're at #1 TDC because the two cast-in marks on the face of the cam gear will be pointing to 3 o'clock.

Here's the marking on the damper showing TDC, but you don't know from this alone whether it's TDC on cylinder 1 or cylinder 6. (Your damper will be black, not orange):



And this pic shows the cam gear marks pointing to 3 o-clock, which indicates TDC #1. (The marks also show where the rotor is supposed to point when mounting it, so you don't have to guess....)




Here's the position on the passenger side where you measure the belt tension, with the engine at TDC on #1. Note that this pic shows a belt that's too loose- this was the belt tension on my GT right after I bought it.

terry gt

This sounds scary , with the questions you are asking . You need some one to HELP you , and or do search on timing belt replacement . Where are you located ? did you change the water pump ? Did you change the tensioner rollers ? How did you set the belt tension ?

MainePorsche

That is your AC compressor.

Agree with Terry above. How does one change a TB, mis-set the belt on a cam gear, if one doesn't know how to hand turn the crankshaft to either 0' or 45' ? Something amiss here.

MainePorsche

Thinking about it Dan, what EXACTLY did you do re: the timing belt service ?

Dan Brock

@Rob Edwards - Thanks a lot! Very helpful my friend! To answer your question, mine is a 1990 GT. When I did my reading, the tension was actually a little on the tight side, however still within the window of the Kempf tool. The thing I think I messed up was that I didn't take my reading at TDC 0. I just took the reading wherever it was positioned when I last parked the car.

@terry gt & @MainePorsche

I'm actually not trying to replace the timing belt - that was done about a year and a half ago has only had a few thousand miles put on it. The owner of the car previous to me said that it was crucial that I check the timing belt tension once per year to make sure it wasn't too loose, so that's what I did last night.

However, since doing so I have a feeling that only 7 out of 8 pistons are firing... or something is off because it's idling at 500RPM.

Does anyone know if the order of the wires you re-attach to the distributor cap on the passenger side are important? Do you think crossing up the order on that could be the problem?

Thanks for the help so far everyone. You've all be awesome!

Rob Edwards

Yes, the order of ignition wires is important. Assuming you're in the U.S (and/or your car is left-hand drive), the passenger side distributor cap wires go to cylinders 4-6-7-1, in that order. The numbers are cast into the cap itself on the front surface, for idiotproofing purposes. On the drivers side cap, the order is 5-2-3-8.

There should also be a sticker on top of the radiator that shows this information as well.

I once accidentally swapped the wires for 2 and 3, the car idled low and ran like crap for the 1 block that I tried to drive it. Hopefully that's the trivial answer to your problem.

Dan Brock

THANKS ROB!

Will go out to my garage tomorrow and give it a check! My guess is that is the problem considering im experiencing the low RPMs as well.

Dan