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Did my timing chain skip a few teeth? by Hank is Here
Started on: 11-23-2003 07:34 PM
Replies: 16
Last post by: fierofetish on 11-24-2003 04:02 PM
Hank is Here
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Report this Post11-23-2003 07:34 PM Click Here to See the Profile for Hank is HereClick Here to Email Hank is HereSend a Private Message to Hank is HereDirect Link to This Post
After much frustration this weekend I have been able to get my GT to run again. Sadly I think the timing chain skipped a tooth or two. My father on the other hand thinks the problem is electrical.
The other week when I left work the car lacked power and finally died going up a hill after about 10 miles. It slowly lost power, bogged down to about 1700 rmp for 20 seconds then totally died.
Today I finally got the car to run. After much frustration I loosened up the distributor. After turning it counterclockwise some the car finally started. I shorted terminals A and B the car really seemed to bog down while I timed it. Once I removed the paper-clip from the terminals the car idled nicely.
I just took the car for a drive, when I started to slow down the car bogged, when I went to park the car I tried to rev it. The car revved to 4500 rmp then died.
Does this problem sound like it is eletrical or a timing chain issue?
Hank

[This message has been edited by Hank is Here (edited 11-23-2003).]

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Dennis LaGrua
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Report this Post11-23-2003 08:08 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaDirect Link to This Post
It is difficult to diagnose a problem such as you have without doing a full scan of the ECM. Assuming that you have first checked for spark and fuel there are a number of possibilites that could cause the car not to lose power or not start. If the timing chain slipped the engine would probably exhibit a miss or backfire. Without seeing the car, I'm guessing ignition but at least check for fault codes and go from there.

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fierofetish
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Report this Post11-23-2003 08:13 PM Click Here to See the Profile for fierofetishClick Here to Email fierofetishSend a Private Message to fierofetishDirect Link to This Post
It sounds more likely that your cat is blocked...chains don't just jump a cog or two and then stay there..they go on jumping, until the timing is so far out the pistons hit the valves and you go nowhere!!!Unless the chain tensioner has gone, it is very hard to jump cogs..it must have at least 1/2 inch more play than normal.I have worked on British cars for many years with timing chains,and have only ever seen them too loose or broken...Now if it was a modern type that uses timing belts, I can see that happening, and in fact have, at my own cost!!!Chain links are rigid, but timing belts have very shallow grooves, and when they become too worn or soft, it is very easy for them to allow the timing pulley to slip a notch or two.It was almost unheard of for mechanical timing chains to jump a cog, until the flexi timing belts came into fashion...now it is a frequent but erroneous diagnosis, in chain driven timing systems. If it seemed to improve by moving the timing, that could be because by doing so, you have reduced the efficiency of the engine, thus giving the cat less work to do!!I would guess that it is your cat...unless you don't have one,which then leaves other possibilities before you look at timing problems...fuel and electrical
Just my 2c's worth, and hope it helps
fierofetish

[This message has been edited by fierofetish (edited 11-23-2003).]

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Report this Post11-23-2003 08:47 PM Click Here to See the Profile for I'm BackClick Here to Email I'm BackSend a Private Message to I'm BackDirect Link to This Post
There should be no chain tensioner on a 2.8 V6. What I would do first is to establish the mechanical state of the engine. I would run the crank to TDC #1 and check the proximity of the valve train. If that checks ok, I would then check fuel pressure. If that's ok, I would then check the cat and consider changing it, as a previous poster wrote.
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Report this Post11-23-2003 09:26 PM Click Here to See the Profile for jelly2m8Click Here to Email jelly2m8Send a Private Message to jelly2m8Direct Link to This Post
Yes there is a timing chain tensioner in a 2.8L V6. It's basically a block to asorb timing chain deflection.

The general consensous is that a timing chain in a 2.8L won't jump a few teeth and stay put. I though this myself untill this past summer.

I had a customers 2.8L Fiero here with a drivability issue. After diagnosing the car I was sure it had a jumped timing chain. I though this wasn't possible and I even posted the question on here. The replies were as I though, won't happen.

Curiousity got the better of me and I pulled the timing chain from the engine, and there was the timing chain, in position, but 2 teeth out of proper Cam -Crank gear alignment.

The only way to actually answer your question is to pull the timing chain and visually check things in there.

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GTDude
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Report this Post11-23-2003 09:38 PM Click Here to See the Profile for GTDudeClick Here to Email GTDudeDirect Link to This Post
NO. 1......chains do jump just a few teeth. I've seen it happen toooo many times.

I have a feeling you have a clogged cat, but the only way to tell for sure is to disconnect it.

As far as timing goes, pull #1 plug and rotate the engine until you can feel compression on the cyl. Look at you timing mark and it should be very near the pointer on 0 degrees. Then pull the dist cap and see if it lines up with #1 on the cap. If all this is correct, it's not the timing.

Don't forget the module......yeah, I know, the module again. The module can simulate electronically a bad timing chain, not enough fuel......and lots of other things.
Good luck!

Phil

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fierofetish
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Report this Post11-23-2003 09:42 PM Click Here to See the Profile for fierofetishClick Here to Email fierofetishSend a Private Message to fierofetishDirect Link to This Post
I suspect somebody had messed with the timing chain..It is impossible for the chain to jump unless it is broken, or the teeth on the cam sprocket are so worn down, or some foreign body has got in and inserted itself betewwn the chain and the gear,or the chain has stretched by more than one inch..that is the amount of play required for the teeth of the cam gear to engage one tooth out, let alone two.The chain is I believe a double type,and the amount of force needed to stretch it enough to jump a cog is more than the gear would stand.
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jelly2m8
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Report this Post11-23-2003 11:29 PM Click Here to See the Profile for jelly2m8Click Here to Email jelly2m8Send a Private Message to jelly2m8Direct Link to This Post
 
quote
Originally posted by fierofetish:

I suspect somebody had messed with the timing chain..It is impossible for the chain to jump unless it is broken, or the teeth on the cam sprocket are so worn down, or some foreign body has got in and inserted itself betewwn the chain and the gear,or the chain has stretched by more than one inch..that is the amount of play required for the teeth of the cam gear to engage one tooth out, let alone two.The chain is I believe a double type,and the amount of force needed to stretch it enough to jump a cog is more than the gear would stand.


Hate to ruin your day, it's been a proven fact that a timing chain will jump the teeth if it's stretch enough, without having severly worn gears and sprockets, or missing teeth.

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Report this Post11-24-2003 01:19 AM Click Here to See the Profile for I'm BackClick Here to Email I'm BackSend a Private Message to I'm BackDirect Link to This Post
 
quote
Originally posted by jelly2m8:

Yes there is a timing chain tensioner in a 2.8L V6. It's basically a block to asorb timing chain deflection.

The general consensous is that a timing chain in a 2.8L won't jump a few teeth and stay put. I though this myself untill this past summer.

I had a customers 2.8L Fiero here with a drivability issue. After diagnosing the car I was sure it had a jumped timing chain. I though this wasn't possible and I even posted the question on here. The replies were as I though, won't happen.

Curiousity got the better of me and I pulled the timing chain from the engine, and there was the timing chain, in position, but 2 teeth out of proper Cam -Crank gear alignment.

The only way to actually answer your question is to pull the timing chain and visually check things in there.

Is it technically termed a, "tensioner?" Can't you TDC #1 and check valve position?

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Report this Post11-24-2003 01:24 AM Click Here to See the Profile for I'm BackClick Here to Email I'm BackSend a Private Message to I'm BackDirect Link to This Post

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quote
Originally posted by GTDude:

NO. 1......chains do jump just a few teeth. I've seen it happen toooo many times.

I have a feeling you have a clogged cat, but the only way to tell for sure is to disconnect it.

Don't forget the module......yeah, I know, the module again. The module can simulate electronically a bad timing chain, not enough fuel......and lots of other things.
Good luck!

Phil


"As far as timing goes, pull #1 plug and rotate the engine until you can feel compression on the cyl. Look at you timing mark and it should be very near the pointer on 0 degrees. Then pull the dist cap and see if it lines up with #1 on the cap. If all this is correct, it's not the timing."

Yes, when there is compression, then stick a wooden dowel into the spark plug hole until you are at TDC - do this by rocking it back and forth to see the 'middle ground.' Then check the valve overlap area, if good, then check the harmonic balancer to be at 0 degrees. The reason you need to check it in this order is that the outer ring on the HB can slip. Then, check the distributor rotor in relation to the #1 cylinder wire. Do it in this order to ensure that all components are where they are supposed to be and functioning/serviceable.

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Report this Post11-24-2003 01:25 AM Click Here to See the Profile for I'm BackClick Here to Email I'm BackSend a Private Message to I'm BackDirect Link to This Post

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quote
Originally posted by fierofetish:

I suspect somebody had messed with the timing chain..It is impossible for the chain to jump unless it is broken, or the teeth on the cam sprocket are so worn down, or some foreign body has got in and inserted itself betewwn the chain and the gear,or the chain has stretched by more than one inch..that is the amount of play required for the teeth of the cam gear to engage one tooth out, let alone two.The chain is I believe a double type,and the amount of force needed to stretch it enough to jump a cog is more than the gear would stand.


tell that to my 83 454 pick up, or a friends AMC whatever the f it was. It is rare, but chains do slip.

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Report this Post11-24-2003 08:26 AM Click Here to See the Profile for avengador1Click Here to Email avengador1Send a Private Message to avengador1Direct Link to This Post
Another thing that slips is the outer ring of the harmonic balancer. If this is off you won't be able to set the timing corrctly as the marks will be off. You will need to determine true top dead center with an indicator gauge, or you would need to replace the balancer. This would be a better idea because if it slipped it is bound to self destruct.
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Report this Post11-24-2003 10:24 AM Click Here to See the Profile for blazin'Click Here to Email blazin'Send a Private Message to blazin'Direct Link to This Post
My '87 GT jumped a few teeth on it's timing chain. I couldn't figure out why it was running so bad after sitting through a winter. I finally turned the motor over by hand to get the #1 piston to TDC, and the rotor button was not pointing at cylinder 1, but at cylinder 3. I popped the dist. out, put it back in pointing at #1, timed it up, and it's worked like a top for 9 months.
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Report this Post11-24-2003 11:06 AM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianDirect Link to This Post
yes, I would think the chain jumping would be the last thing to look for. clogged cat or low fuel pressure are good places to look.
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Hank is Here
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Report this Post11-24-2003 11:14 AM Click Here to See the Profile for Hank is HereClick Here to Email Hank is HereSend a Private Message to Hank is HereDirect Link to This Post
I am leaning towards the timing chain for several reasons.

When I tried to start the car I disconnected the cat, the car still would not start.
The fuel pressure is approx 44 PSI, so that is well within spec. In an act of desperation I loosened the distributor, played with the positioning and it finally started, with the cat disconnected. I then reconnected the cat, it continued to run and would start after the timing was readjusted. Also when timing the car the timing mark on the crank seems to jump around a fair bit.

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Paul Prince
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Report this Post11-24-2003 11:24 AM Click Here to See the Profile for Paul PrinceClick Here to Email Paul PrinceSend a Private Message to Paul PrinceDirect Link to This Post
I would take the dist. cap off and unplug the gray and black connectors from the coil, turn the engine with the starter and watch the rotor, if it hesitates, then your chain is prolly really bad.
I suppose it could be electrical (ign. module, ECM), but I would eliminate the mechanical side first.........Paul
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Report this Post11-24-2003 04:02 PM Click Here to See the Profile for fierofetishClick Here to Email fierofetishSend a Private Message to fierofetishDirect Link to This Post
I am sorry, but purely from valve-to -piston timing, you cannot rectify a timing problem by taking out the distributor and re-positioning it(how did it jump whilst being in winter storage? it must have happened before being laid up,or after the end of winter, when you tried to restart it) because then the piston position to valve position to distributor position will ALL be out.For example
:in a perfectly timed engine, the piston arrives at top dead centre as the valves are both shut, and the distributor will have caused a spark in the relevant cylinder the number of degrees in advance recommended in tuning instructions. Now, if the timing chain has allowed the cam to rotate out of position by say 3 cogs, the timing relationship between the pistons and the valves will be in the region of 10-15 degrees retarded,but the valves will still be opening at the correct time in relation to the distributor firing, because valves and distributor both run off the camshaft.So now the piston has hit top dead centre, and 20 degrees later the valves are fully closed, and the distributor fires the sparkplug.Result is an engine which will not run very well,if at all. Now, if you alter the distributor position to fire in conjunction with the piston timimg, you will have the distributor firing the plug in sync with the pistons, but not with the valves, which will still be 20 degrees short of fully closing.If you were to set up an engine like this, you would be in deep trouble.In every case of "jumped timing chain" that I have ever worked on, it has turned out to be somebody has tried to upgrade a camshaft, or for some reason dismantled the engine, and when reassembling it, has moved the cam the wrong way when they find you cant get the chain on,because the links haven't lined up to the teeth, and so they have moved the cam pulley in order to get the chain on, and then gone on to finish the reassembly, only to find the engine doesn't run....then can't stand the thought of all that work to be re-done, and call in a garage to fix a "jumped timing chain".This has been my findings 100% in forty years of working on CHAIN DRIVEN timing problems.As i mentioned before, with belt driven timing,the problem happens all the time if you don't change it at recommended periods. Even with a timing chain being old and stretched, it has to completely rise above the perimeter of all the teeth on either of the cogs in order for the cog to rotate freely from the chain.It can't jump one cog at a
time.
FF
PS I do believe in never saying never, and will always accept being proved wrong!!

[This message has been edited by fierofetish (edited 11-24-2003).]

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