Well, just finished replacing head gaskets on my old beater, which I love. Got it all back together, added fluids and cranked her up. Couple fits and starts but started running, albeit rough and smoky at first. Seemed as if there was a timing issue. After double checking my plug wires and the distributor, I pulled it out and dropped it back in to see if maybe I had put it in off by a tooth. Seems to run much better now, but I do have to rotate it CCW to the fullest amount for the smoothest running, which really is pretty smooth (occasional miss, but it's an old engine). However, I'm not so sure that's really the best mode of running or timing. Any thoughts?
Rotor points to #1 cylinder at TDC, and everything seems in order. But, is it likely that the distributor is still off by a tooth? Doesn't seem like it, as I doubt it would be running as smoothly as it is.
Also, as for the oil. Drained, new filter, and refilled. However, very peculiar in that I have five quarts in it and still NO reading on the dip stick! Since there is an aux cooler up front, which I always thought was for the tranny, I'm wondering if it's actually for the oil and I just have an extra large oil capacity, which is fine. But, I thought I'd ask, is there any other thing that could cause the dip stick to be showing no oil line?
The oil pan only holds 4 quarts, so something is up if you can't see the oil level after adding 5. Are you sure it isn't just clean oil on the dipstick?
Timing should be about 15° BTDC.
The timing belt could have jumped a tooth, also. How many miles has the timing belt been on there? It is supposed to be replaced every 60,000 miles.
Thanks much for the feedback. Sure enough, the oil was indeed on the stick. It was just so clean that it was tough to see. (A good problem!)
You also answered my question about the timing... use a timing light to check degrees before TDC. I couldn't find any source to confirm use of a light.
My truck seems to start okay, runs rough when cold, but runs fine and strong by the time I get home (it's warmed up). I'm really hoping I don't have an issue with the timing belt. I just replaced it and hand cranked the engine through a couple cycles to confirm no valve collisions, which it did not have.
There is a Trouble Diagnoses section in the 1994 Service Manual in the EF & EC Section that deals with the engine stalling when cold (the closest I could find to your issue). It says to check 1) the IACV-Air Regulator and IACV-AAC Valve, 2) the Injectors, 3) the Spark Plugs and Wires, and 4) the Fuel Pressure (including a clogged fuel filter).
It sounds like either the timing belt was installed a tooth off when the heads were replaced or the distributor was installed incorrectly. Usually you can see a shadow of the hold down bolt washer on the distributor base where it was originally set at, which should be just a hair off from the center of the adjustment groove. Always verify timing with a timing light. Remember that the distributor is driving off of the gear on the left camshaft, so if the left camshaft or the crank is not properly timed, it will affect the distributor timing.
Well, after being out of commission for a week with the flu (working in cold garage late at night whilst also having a cold = getting the flu) I've just now gotten a chance to put that timing light on it. It's waaay off of 15 degrees BTDC, closer to 25 degrees ATDC, when it's running it's best. If I turn the distributor back to 15 d BTDC, the engine nearly dies. This makes me think that smj99smj may well be right in that my belt is off by one tooth. I will be checking the computer codes, however, before cracking into the timing belt task.
Biggest challenge I anticipate in checking belt is possible need to remove the main pulley. I don't have an air ratchet hammer (if that's the correct name), and though the electric one I rented to loosen the main bolt initially worked very well, it's large size does require dismantling the front of the truck (coolers, grill, bumper, etc). Hopefully I can simply remove the top half of the belt dust cover, allowing the belt to stay wrapped around the lower main gear while I slip it off either of the top cam gears to make a necessary adjustment. (BTW, does anyone know any tricks for grasping and carefully rotating a cam w/o a special "Gear Holder" tool? Can this just be done with a wrench on the cam timing gear mounting bolt?)
Still, all this said, I DID confirm proper timing belt / gear positions before buttoning up the front of the engine.
And, also, from a practical perspective, last thing I want to do about now is spend another late night working in a cold garage... while trying to recover from the flu.
jp2code,
Thanks much for the tip about tapping a breaker bar. Works great!
Sure enough, it looks like the passenger's side cam is one tooth off, when I compare it to the driver's side cam and the main pulley.
Another question: Is there a "real" method for identifying TDC on the main crank gear when pulley is off? Previous owner left a paint dab, and a felt pen mark to line up. But I don't see any marks formed into the cast, for example, to line up with the spline on the crank or divot on the gear, again, for example. Only proper method I see is to put the pulley back on an use the timing marks, which I don't think actually is a workable method.
One trick I've seen when it comes to loosening and tightening the crank pulley bolt is using a hold-down strap (or utility strap) run from the frame rail, around the crank pulley multiple times and then back to the same frame rail.
There is "supposed to be" an alignment mark on the oil pump that lines up with the crank sprocket timing mark. Honestly, forget about the timing marks on the engine! I never use them. Crank sprocket mark at 5:00 position. Right bank cam sprocket mark at 11:00 position and left bank sprocket timing mark at 1:00 position. It is matching the timing lines on the timing belt with the marks on the sprockets that is what matters. If the lines are worn off the belt, get a new belt! Arrow on belt should point to the front of the vehicle and on most belts, will sit in the span between the two cam sprockets. Dotted or dashed line on the belt lines up with the right bank cam sprocket timing mark. Then, the two solid lines should mate with the left bank cam sprocket and crank sprocket timing marks, respectively. Turn the cams as needed to get the marks and lines to line-up. If you line up the marks on the sprockets with the correct lines on the belt, the engine will be in time at TDC #1 .
Thanks very much for all the tips RE the timing belt and other, above. Used smj99smj's method in placing the belt on the pulley's. Worked very well. In retrospect, I'm not sure that I was off by a tooth at all. In any case, I'm certain that it's now installed and synched correctly. Engine still running about the same, poorly. Haven't had a minute to get back at it; thought I'd check the computer for error codes. Reading my Haynes Guide again, air leaks at the intake manifold are listed as reasons for "Engine misses throughout driving speed range" and also "Engine lacks power" symptoms. This seems worth looking into since I obviously had the mani off, and its seems to me to be one of those issues that was fine before my valve gasket work and now is very poor, unlike other possible causes like spark plug gapping, fuel filter clogged, cracked distributor cap, and others. (They likely would not suddenly change from "fine" to "failed" with the gasket work.) I also want to look into the IACV-Air Regulator and IACV-AAC Valve that jp2code mentions, above.
It seems like there was a specific order that the intake manifold had to be assembled, like torque all bolts in specific order to 7 ft/lbs and then tighten them all down again to 25 ft/lbs.
Thanks very much, Joe. Do you know if there is any accepted best practice regarding the use of gasket sealants with the intake manifold (and air collector for that matter)? Use it? Don't use it?
Thx!
When I took my intake off, I did not use anything but the replacement gaskets that came with it. Nothing in the manual said anything about adding any sort of contact cement and there was nothing existing there when I pulled it off.
That said, whenever I finished, I had spots that apparently didn't seal completely, too (I replaced the knock sensor).
I wound up paying the Nissan dealership $400 to fix my fubar.
If the gaskets have a rubber seal or sealant around the ports, just install them as is. If the gasket is nothing but stamped sheet metal, I use copper spray gasket to coat them on both sides before installing; let the spray gasket dry for a few minutes so it will get tacky before installing. There are several designs that manufacturers use for these gaskets, which is why I can't give you a specific answer.
Okay, I just now confirmed that I indeed did a poor job of tightening down the intake manifold nuts and bolts. I left them all to be very low, something under ten ft/lbs of torque, perhaps under 5 (my torque wrench isn't very accurate that low). Shortly I'm going to start re-torqueing. But, before I do, I thought I'd double check the recommended specs. I have two sources that both seem to call out (max's) of:
Bolts: 3.6, then 14 ft. lbs.
Nuts: 3.6, then 20 ft. lbs.
Does anyone have any sources indicating that they ought to be higher?
It's my hope that the air leaks that must be resulting from the low torques that I applied to the manifold are the primary reason the engine is running so poorly, with symptoms of timing that must be way advanced for the engine to run, and a rich smell of un-burned fuel gas in the exhaust.
BTW, the online downloaded service manual seems to have a typo on this topic. On page EM-33, for the VG30E, it shows a series of three torque-down steps. It appears that steps #2 and #3 are identical, both terminating at max toque at what I've listed above. (ie, 3.6, then 20, then 20 ft. lbs.) This would seem to make step #3 mute. Am I missing something?
You don't back off the intake bolts/nuts after the first series of 20 ft/lbs. You just simply go back and redo the sequence to make sure they are all at 20 ft./lbs.
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