Cam chain and camshafts -> HOW TO
12-10-2004, 01:24 PM
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Cam chain and camshafts -> HOW TO
Troubleshooting 89'GT rich mixture condition it seems that intake camshaft is late. Now could it be that intake cam is installed one teeth off on cam chain. Is there any online procedure where a proper way of installing camshafts on chain is described (Did a search in forum - did not help...)?
Last edited by martini928; 12-10-2004 at 02:30 PM.
12-11-2004, 05:05 AM
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Wait untill tomorrow. Questions seem to get answered in spurts around here. Somebody will know your answer.
I just noticed that you're in Latvia. I'm looking into getting a masters degree in Latvia or Estonia.
I just noticed that you're in Latvia. I'm looking into getting a masters degree in Latvia or Estonia.
12-11-2004, 07:32 AM
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There is a load of info in the WSM on the set up, special tools to set the cams etc. IIRC there are only12 or 13 teeth on the cam chain wheels, and to be one out is a lot, so I think it would show up immediately on start up after work in there, its not something that would creep up on you. Exactly what symptom are you trying to solve? How rich is the mixture? Is it only on one bank? Couldnt it be a leaking injector? Is one plug dirtier than the others?
jp 83 S
jp 83 S
12-11-2004, 11:14 AM
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Hi.
The camshafts are marked in relation to one another. There is a little straight line that you use on 85-86 camshafts and come 1987s. On most 1987 and later units you have to measure about 113mm if I recall from nub to nub-a cast point in the camshaft right next to the chain gear toward the front of the engine. This tells you if the camshafts are in correct orientation with one another.
Good luck
The camshafts are marked in relation to one another. There is a little straight line that you use on 85-86 camshafts and come 1987s. On most 1987 and later units you have to measure about 113mm if I recall from nub to nub-a cast point in the camshaft right next to the chain gear toward the front of the engine. This tells you if the camshafts are in correct orientation with one another.
Good luck
12-11-2004, 11:21 AM
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The cam shafts on the '89GT are not marked as indicated in the WSM. I have yet to find in the WSM the procedure for determining the relative timing between the intake and exhaust cams - but I'm still searching.
I agree with JP that the cam timing is the last thing I'd check for a rich mixture. More likely it is the MAS, injectors, or something else directly related to the engine management system and components.
I agree with JP that the cam timing is the last thing I'd check for a rich mixture. More likely it is the MAS, injectors, or something else directly related to the engine management system and components.
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12-11-2004, 03:16 PM
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The WSM shows two kinds of alignment marks on the cams (straight line on the sprocket boss, cast hump next to it), and shows that you align the marks straight up with seven links of chain between the marks.
That being said, I haven't looked at the cams on my '90 GT to see if the marks are there...
The cam timing is given, so you could use that to check the alignment of the cams...
On the '89 GT, the intake opens three deg ATDC and the exhaust opens thirty deg BBDC.
That being said, I haven't looked at the cams on my '90 GT to see if the marks are there...
The cam timing is given, so you could use that to check the alignment of the cams...
On the '89 GT, the intake opens three deg ATDC and the exhaust opens thirty deg BBDC.
12-15-2004, 02:37 PM
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Feeeww...
No that really was the problem and cams really have pointers :-)
Now the adjustment specs for cam timing: Are those true for 89GT?
For cylinder bank 1-4, it's 2.8 +/- 0.1 mm
For cylinder bank 5-8, it's 3.1 +/- 0.1 mm
Just cant wait to see how the car will go after adjustment - means that my car never worked the way it should - with so late intake...
No that really was the problem and cams really have pointers :-)
Now the adjustment specs for cam timing: Are those true for 89GT?
For cylinder bank 1-4, it's 2.8 +/- 0.1 mm
For cylinder bank 5-8, it's 3.1 +/- 0.1 mm
Just cant wait to see how the car will go after adjustment - means that my car never worked the way it should - with so late intake...
12-15-2004, 02:52 PM
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Martins: PM me your email address. I have a video that shows how cams are installed and aligned. Make sure you have a large storage limit.
12-15-2004, 03:04 PM
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Originally Posted by martini928
Feeeww...
No that really was the problem
No that really was the problem
and cams really have pointers :-)
Now the adjustment specs for cam timing: Are those true for 89GT?
For cylinder bank 1-4, it's 2.8 +/- 0.1 mm
For cylinder bank 5-8, it's 3.1 +/- 0.1 mm
For cylinder bank 1-4, it's 2.8 +/- 0.1 mm
For cylinder bank 5-8, it's 3.1 +/- 0.1 mm
12-16-2004, 02:26 AM
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BigDave - thanks a lot but its already too late...
Worf928: Yes the beer made a lot of a problem by the next morning :-) Real problem was that the intake cam was one teeth of on a chain, so it opened valves late -> lower compression on one side -> not completely burned fuel -> rich micture -> this solves the problem and makes me think that the guy who assembled the engine for me after I bought the car is one to blaim!
Cams had those upward pointers for putting them on a chain but those were not the nicest words what mechanic said about them :-) Those are welded or something - not really white and not so obvios.
Not really using WSM procedures, but mechanic is the one I finally can trust :-)
Worf928: Yes the beer made a lot of a problem by the next morning :-) Real problem was that the intake cam was one teeth of on a chain, so it opened valves late -> lower compression on one side -> not completely burned fuel -> rich micture -> this solves the problem and makes me think that the guy who assembled the engine for me after I bought the car is one to blaim!
Cams had those upward pointers for putting them on a chain but those were not the nicest words what mechanic said about them :-) Those are welded or something - not really white and not so obvios.
Not really using WSM procedures, but mechanic is the one I finally can trust :-)
12-17-2004, 02:16 AM
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Originally Posted by martini928
Troubleshooting 89'GT rich mixture condition it seems that intake camshaft is late. Now could it be that intake cam is installed one teeth off on cam chain. Is there any online procedure where a proper way of installing camshafts on chain is described (Did a search in forum - did not help...)?
If it feels like your GT is only running on 4 cylinders and the exhaust has unburnded gas, one of your "two" ignition systems could be bad (coil, coil wire, final stage, etc). From '89 onwards, there is a special circuit that monitors manifold temperature and shuts off the fuel injectors to the cylinders of the engine that are "cold."
When ignition circuit 1 (cylinders 1,4,6,7) is shut-down, a red LED is illuminated.
When ignition circuit 2 (cylinders 2,3,5,8) is shut-down, a green LED is illuminated.
Leaking fuel injectors could be the problem. Quite often the MAF or the LH fuel injection controller are the cause of the problem.To check the MAF, run the engine until warm. Unplug the conncetor to the MAF (under the air box), start the engine. If it runs better, not as rich, your MAF is likely the problem. If it makes no difference your LH Fuel injection module could be going bad. One of the failure modes is an over rich fuel mixture.
If you know anyone who owns an S4 or newer 928 (doesn't have to be a GT), borrow their module and plug it into your LH connector and see if the problem goes away. If it does, time for an LH rebuild. If you can't locate a "test" LH, send yours in to a reputable shop for inspection.
12-17-2004, 06:35 AM
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Problem solved...
No finnaly I can state -> Yes it is possible that intake camshaft is off by one teeth on a camchain (intake valves opens late) and it creates a rich condition, but car is drivable and the only thing is a little roughtness in idle if this happened on one side of the V. First thing to check is the compression and in this case it was low on the side, where the intake cam was late - so it leeded to the trobleshooting this issue.
Now I am really impressed by this engine as such a mulfanction still could spin the tires :-)
Cams reasembled correctly and adjusted - engine running smooth and nice!
Can't wait for a test drive!!!!
Big thanks to everyone for input - Rennlist is the best! :-)
No finnaly I can state -> Yes it is possible that intake camshaft is off by one teeth on a camchain (intake valves opens late) and it creates a rich condition, but car is drivable and the only thing is a little roughtness in idle if this happened on one side of the V. First thing to check is the compression and in this case it was low on the side, where the intake cam was late - so it leeded to the trobleshooting this issue.
Now I am really impressed by this engine as such a mulfanction still could spin the tires :-)
Cams reasembled correctly and adjusted - engine running smooth and nice!
Can't wait for a test drive!!!!
Big thanks to everyone for input - Rennlist is the best! :-)