I have a 2000 Nissan Xterra 3.3L, at 114,000 miles I changed all the belts two days ago these being 3 serpentine asscesory belts and the timing belt with tensioner. I do believe that the engine did not move (cams & crank) while replacing timing belt and even made sure the timing marks all lined up on the cams and the crank upon installation. The belt tension on timing belt was done to Chilton Spec. as well. I did not tighten the serpentines to spec. , but just to best judgment. Between idle -to- 3000 the engine does not seem as strong especially up hill. It idles smooth, does not over heat and there is no tapping/knocking or a check engine light. I was told that that with new belts (especially the timing belt) the motor may have to wear to the belts or vice versa and there may be some power loss till all wears in togather do to now tighter tolerances. I was going to relieve some tension on the serpentines to see if maybe that would make a differeance in regaining power. Has anyone ever heard of this problem when repacling all the belts espcially the timing or does anyone have any other suggestions to what might have causesd this slight loss (15%-18%) of power loss?
Did the Chilton spec include loosening the rocker arm shaft nuts prior to setting the timing belt tensioner?
Tester
Nothing in the process in changing any of the belts involved loosening a rocker arm or bolts. The only thing that was in need of loosening was the tensioner which was replaced with a new one. The belt tension was set to 0.5-0.6 with 22lbs of force at the top center defelction point between the two cam shafts along with the specified feeler gauge inbetween th etension with a thickness of around .014 as described in Chilton Manual
Since this vehicle has a distributor, maybe the ignition timing has gotten retarded a bit. JMHO, but any timing belt job that involves a distributor should always have the timing checked as a final step.
Just something for consideration anyway as retarded timing can make an engine pretty anemic.
Here’s what it says probatum.
Make sure cylinder one is at TDC and all timing marks line up.
Remove the valve covers.
NOTE: The rocker shaft bolts must be loosened prior to setting the timing belt tensioner in order to aquire the proper timing belt tension.
Retighten the rocker shaft bolts and reinstall the valve covers.
Tester
My mistake it is not a Chilton but a Haynes Manual, however starting from page 2B-5 section 7 it does not say anything about removal or loosing of rocker arm in the Haynes Manual. I do not see any reason why the rocker arms would need to be loosed in order to change timing belt or its adjustment from what I have been reading. Any other suggestions?
I don’t see why the rocker shafts would need to be loosened either. But then, I didn’t design the engine.
Tester
No harm done to verify the ignition timing is correct with a timing light on the crank pulley – you may have to set the ECM to open-loop, check your Haynes for the procedure. That’s easy to do. I doubt that is the problem though. Changing the timing belt or any of the other belts doesn’t change the ignition timing I expect. And I doubt the problem has to do with belt tension on the accessory belts – if you have 1/2 to 3/4 inch of play in the belt at the midpoint between pulleys, close enough to make the car run correctly at least. And from what you say it looks like the timing belt tension is adjusted to the procedure, so I doubt that’s the problem. And I don’t think breaking the timing belt in will help. If it ain’t working now, it’s not going to work until you fix it up good and right.
I agree w/@tester that this appears to be a timing belt installation problem.
There was a call on CT a while ago about a caller having a problem similar to yours, setting the timing belt timing marks on a dual overhead cam engine, where the timing belt is routed over two separate cam sprockets. The brothers said this is a very difficult procedure, easy for the inexperienced to make a mistake, and must be done exactly as spec’d in the shop manual for the make/model/year. Otherwise the symptom you are reporting – or worse – will occur; i.e. you are off a notch or two . (They said doing this job for a car with a single cam sprocket is much easier. I can verify this, as my Corolla – while being a dual overhead cam – has only one cam sprocket to route the timing belt around. The other camshaft is driven from the first by gearing.)
For a timing belt install procedure, me, I wouldn’t rely on anything but the shop manual or a Motor manual. The other manuals do a good job for most things, but they have to cram the information for several years and several models into one manual, and sometimes they have to leave out important specifics which only apply to certain years and models to make everything fit in one book. If I didn’t have access to either the shop manual or the Motor, then I’d look up the procedure online on AllData. That service is usually pretty reliable. But not always, so I’d confirm it by asking here and Googling “timing belt installation procedure for make/model/year” first.
Be sure to verify the igntion timing first, but I expect once the timing belt is aligned correctly, the problem you are having will disappear. Best of luck.
@XterraddoG60, did you turn the crank through 2 full revolutions and check that the timing marks were still spot on before putting everything back together?
@db4690 … I’m not sure if what I did on my Corolla is recommended – it’s possible it isn’t safe to do exactly, for either the mechanic or the engine, so I’m not recommending this – but after doing what you said above, a static timing mark check – then I put everything back together except the timing belt covers, which I left off, and verified the timing marks were spot on with the engine idling, using a timing light. Once I was convinced the timing belt was aligned correctly this way, only then did I put the timing belt covers on.
XterraddoG60 - you asked for advice, then argued with one of the most knowing posters on the site.
@GeorgeSanJose, yeah, I’ve occasionally gone that extra step also.
@XterraddoG60, I’ve done several timing belt jobs in the past few years and some of them involved cars with adjustable ignition timing.
On occasion, even though the timing marks were perfect (at least I thought so), I still had to verify and slightly adjust the ignition timing.
But I must say, it wasn’t far off.
I went back in and moved the belt by one tooth. It did remedy the power loss between idle-to-3000. However the idle is now slightly ruff. I turned the distributor and it helped the idle out some but it is still a little ruff and now the check engine light has come on. Now im really puzzled. (Plugs, wires and rotor cap have been recently changed with high quality NGK.)
Here’s a cut and paste regarding the procedure that Tester alluded to.
CAUTION
Before installing the timing belt, confirm that the No. 1 cylinder is set at the TDC of the compression stroke.
- Remove both cylinder head covers and loosen all rocker arm shaft retaining bolts.
NOTE
The rocker arm shaft bolts MUST be loosened so that the correct belt tension can be obtained
(The caps in the last statement are not mine)
Regarding the turning the distributor thing, you really need to do this with a timing light and by following the correct ignition timing procedure.
Back in the old days one could set the timing by ear; at least to an acceptable degree. With modern era cars it’s not so simple and improper setting of the distributor could lead to a wiped engine.
I might also add that you should take info in many Chiltons and Haynes manuals with a grain, or more, of salt. They have inaccuracies much the same as ALLDATA.
Even factory service manuals have flaws.