Jump to content

Find TDC with a frozen #1 plug


dglywasky
 Share

Recommended Posts

Hey Gents (and Ladies?)

New again member (after several years) - have a 96 Path XE 4wd V6 3.3L and was chasing an idle issue. As I have tuned it so I can drive I believe I still have a timing issue. When I check timing, the marks jump around with timing gun, to get engine to run happy (sounds best) I had to adjust distributor way off. Runs ok but want to truely double check timing.

 

My problem is, my #1 plug (and only this plug) is stuck will NOT come out or go in, dont want to mess with it.

 

So how can I determine TDC without removing the #1 plug?

 

Any help would be greatly appreciated. Ive spent a great # of hours in garage tuning so I can drive but I dont want to cause long term damage if timing is off.

Link to comment
Share on other sites

When my distributor was truly bad. We found it because my timing would wander and never stay steady. Took the distributor off and sure enough the shaft had a ton of play and shift around effectively change the timing.

Link to comment
Share on other sites

+1 on the dizzy, and on at least checking the condition and tension of the timing belt (especially if you don't know when it was done last).

 

The only way that the marks on the crank pulley will display incorrect timing is if either the keyway between the balancer and the crank has sheared (which finding TDC manually and comparing could identify) or some numbnuts put the pulley on wrong. The pulley has six bolts, so it can go on five wrong ways and one right one. If the pulley's on wrong, the engine wouldn't care but the timing marks would appear at least 60° from where they should be when you looked at it with a timing light.

 

You could also check for top dead on #4 instead of #1. Looking at a picture of a VG30 short block, and thinking about the firing order, I'm pretty sure #1 and #4 should be at top dead at the same time. Three cylinders fire per crank revolution, firing order is 123456, so 1 and 4 must be synched up.

Link to comment
Share on other sites

Four stroke, so not three firing at the same time. Some would be firing, some on compression stroke. Three firing at the same time on a 6 cylinder would require a two stroke. Which would be awesome power, a two stroke 3.0L V 6.

Link to comment
Share on other sites

+1 on the dizzy, and on at least checking the condition and tension of the timing belt (especially if you don't know when it was done last).

 

The only way that the marks on the crank pulley will display incorrect timing is if either the keyway between the balancer and the crank has sheared (which finding TDC manually and comparing could identify) or some numbnuts put the pulley on wrong. The pulley has six bolts, so it can go on five wrong ways and one right one. If the pulley's on wrong, the engine wouldn't care but the timing marks would appear at least 60° from where they should be when you looked at it with a timing light.

 

You could also check for top dead on #4 instead of #1. Looking at a picture of a VG30 short block, and thinking about the firing order, I'm pretty sure #1 and #4 should be at top dead at the same time. Three cylinders fire per crank revolution, firing order is 123456, so 1 and 4 must be synched up.

Thanks for the input... I had to put my troubleshooting on hold for a few days - wife in hospital... so timing wasnt the most of my concerns. But now back to business

I appreciate the input. My distributor points looked ok (just cleaned em some more) and rotor looks ok.

My timing belt is fairly new... replaced approx 1 year ago when found leaking H2o pump. I reused by time belt tensioner though (long story - trying to match mechanic work before me) so perhaps it has gone bad and maybe I jumped a tooth? I will tear-down and check alignment marks vs dist rotor position vs # of teeth in next day (I hope)... and put on new tensioner which I still have in box on my shelf.

 

I didnt understand the post about the pulley has 6 bolts so can go in wrong 5 ways... crankshaft pulley only has key-weigh and center bolt (1 way) and tensioner puller only has 1 bolt but cambered. Can you clarify what pulley you are referring?

 

Great idea on #1 and #4 being sync'd up... this will help.

Link to comment
Share on other sites

The crankshaft pulley has the pulleys for all the belts. The pulley is attached to the harmonic balancer which then is bolted down with 6 bolts to the harmonic balancer. The harmonic balancer is what is slotted in the keyway of the crankshaft snout.

  • Like 1
Link to comment
Share on other sites

I just looked up a few pictures of the R50 balancer and I see the confusion now--the pulley appears to be one with the balancer. I assumed it was the same design as the WD21 with a separate pulley that bolts on. Learn something new every day! Sorry for the confusion.

 

There's more to the distributor than the cap/rotor. There's an angle sensor under the rotor that causes timing issues when it starts to fail, or when the bearings supporting the distributor shaft wear out.

Hope your wife's alright.

  • Like 1
Link to comment
Share on other sites

Thanks... she is out and feeling better but they dont really know what it was. So good news ??? I guess... some parallels to my Pathfinder (dont tell her I said that).

 

For those looking to checking TDC with #1 piston stuck.... as Coung Nguyen suggested (correctly) I took all plugs out, and distributor cap off, rotate crackshaft as distributor rotor approaches #1 position you will start to feel resistance (this is compression stroke) you will then have to judge when is highest resistance. Also, #4 does also seem to reach TDC at same time.

 

For my situation: Tore down to timing belt, spacing of teeth between cam shaft mark to cam shaft mark and cam shaft mark to crank shaft mark ok, belt looks in good condition (it should with less than 20k on it) crack-shaft pulley / damper seem in good condition (no separation etc) and crank-shaft pulley at TDC when timing marks aligned and distributor rotor points to #1 position. So, mechanically I seem to be ok... so good news. Now what is wrong? From previous post of Slartibartfast I suspect the distributor assembly (including the angle sensor).

Upon reassembly, I am thinking to install the new belt tensioner - just seems to be very stiff, does not free spin a bit when I turn it. I checked at auto parts place another new tensioner and seems the same. It just feels wrong vs the one that is installed which seems to have smooth rotation which continues to turn when you spin in your hand (doesnt continue for a long time like no resistance it just feels like how you would think it should).

 

I will look into and report back.

 

 

Link to comment
Share on other sites

  • 2 weeks later...

RESOLVED!!!

 

Ok as the title of this thread doesnt match all content - I will report here and will post a new subject to hopefully help someone else out.

 

My root problem was an idle issue: had 3 problems: 1} fuel line leak - fixed with flex line replacements 2} Large vacuum leak - fixed by replace lower intake manifold gaskets and the creme-de le-crem 3} CAM SHAFT position sensor (in distributor assembly).

 

From research and suggestion from Startibartfast (thanks bossman) looked at distributor. Replaced with junkyard part, re=adjusted position on idle from service manual and BAM smooth as silk.

 

Also - when checking timing... you will see from previous posts that I questioned the timing belt tensioner. I did NOT remove/replace/adjust the tensioner, belt etc. I didnt want to introduce another variable.

 

Thank you to the forum and your suggestions it was so helpful.

 

As said, I will post another topic with subject on the idle issue I had and provie information on the fix, hopefully will help someone.

 

Thanks again

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...