Head scratcher

[Erik the Awful]

I liked them right up until Renault bought them out, but Nissan had no other way forward. They were half a billion in the hole and had even quit making Z cars. As bad as it sounds, Carlos Ghosn's extreme cost-cutting measures saved them. Now they need to turn their reliability around before they Mitsubishi their reputation.

 

[L31MaxExpress]

I liked them right up until Renault bought them out, but Nissan had no other way forward. They were half a billion in the hole and had even quit making Z cars. As bad as it sounds, Carlos Ghosn's extreme cost-cutting measures saved them. Now they need to turn their reliability around before they Mitsubishi their reputation.

The CVT and their stubborn desire to keep that POS around is the biggest part of their reliability issue. RWD stuff luckily has a normal automatic.

 

[L31MaxExpress]

I messed with it a bit this afternoon cutting injectors off and messing with stuff attempting a further diagnoses. At idle, all 8 cylinders are contributing equal power. At 2,000+ rpm all 8 cylinders are contributing equal power. At 1,750 rpm, cylinder 3 is dead, 4 and 7 are weak. I repeated the same test multiple times and same results every time. I actually advanced and retarded the ignition timing at 1,750 rpm to alter the rotor phasing to see if it was the timing advance at 1,750 rpm causing the issue. Stayed the same. If I play with the throttle between idle and 4,000 rpm it shows a large misfire count climbing on #3 and some misfiring on #4 and #7. About a year ago I fought a #4 misfire that acted similar. Did a Cap, Rotor, Plugs, Wires and lifter adjustment. At 1,750 rpm it sounds like it nearly has collapsed lifters in it. The valvetrain was absolutely sounding horrible. Honestly now feel like it is probably all lifter related. It has crossed my mind to go to the shop, grab the cam, lifters, intake and 24x stuff and shot gun it all into place. I want to get the longer pushrods into it and verify the intake is not leaking before tearing the top end apart but it is looking like that is going to be the ultimate solution. I want to test the longer pushrods and the greater lifter preload because I have 2 or 3 other sets of new GM LS7 lifters that I really want to be able to use in future builds. There are guys running over 400# open spring pressure on some builds with them, so I do not understand why mine seem to hate the 350# spring pressure.

I took it down the road a few miles outside of town, turned around, layed into from a stop, WOT all the way to 80 mph and not a single misfire count. Exactly opposite of what I would expect from any kind of ignition system failure too.

 

[Sean Buick 76]

Very frustrating! Can you use a dial indicator to check rocker lift?

 

[L31MaxExpress]

Very frustrating! Can you use a dial indicator to check rocker lift?

It is possible to do, would need to bottom out the hydraulic lifters first. Are you thinking wiped cam lobe(s). It is a hydraulic roller cam and nothing gives me that kind of failure sign. This has a completely different sound, it just sounds like it is losing lifter pre-load at 1,750 rpm and sounds like it has multiple loosely adjusted rocker arms.

 

[Sean Buick 76]

It is possible to do, would need to bottom out the hydraulic lifters first. Are you thinking wiped cam lobe(s). It is a hydraulic roller cam and nothing gives me that kind of failure sign. This has a completely different sound, it just sounds like it is losing lifter pre-load at 1,750 rpm and sounds like it has multiple loosely adjusted rocker arms.

Yeah I didn’t really think a lobe was going away but just looking to see if there is a way to test the lifter health by watching the lift? Being a hydraulic lifter doesn’t help any testing ideas as you say.

I guess what I’m picturing is the dial indicator on the rocker while it’s revved up to monitor the lift but I’m guessing it only acts up under load.

I think the valve noise is your clue that you have sone bad lifters. We have issues with all lifters these days it seems.

I finally went solid lifter on my Buick but it’s rarely driven so it’s not an issue to check them. Not saying that’s your solution either.

 

[L31MaxExpress]

Yeah I didn’t really think a lobe was going away but just looking to see if there is a way to test the lifter health by watching the lift? Being a hydraulic lifter doesn’t help any testing ideas as you say.

I guess what I’m picturing is the dial indicator on the rocker while it’s revved up to monitor the lift but I’m guessing it only acts up under load.

I think the valve noise is your clue that you have sone bad lifters. We have issues with all lifters these days it seems.

I finally went solid lifter on my Buick but it’s rarely driven so it’s not an issue to check them. Not saying that’s your solution either.

Hindsight being 20/20, should have just gone with a small, tight lash solid roller using a step nose roller camshaft ground for the solid roller lifters. Then used the solid roller lifters that drop in place of the hydraulic lifters. I have honestly been tired of hydraulic lifters for 15 years myself. Solid lifters can hold adjustment for a ton of miles without issue.

 

[Sean Buick 76]

Agreed, good detective work though!

 

[Sean Buick 76]

Not that this is your issue, but for discussion:

You got me thinking about your combo and I’m not sure how much of a gain the roller cam is in your case. Flat tappet cams outperform roller cams in the lower lift numbers. Your cam profile is very mild, and likely doesn’t showcase the inherent advantages the roller design offers. Plus there are a few drawbacks to the roller, cost and weight. The extra valve-train weight means stiffer valvesprings and energy absorbed. Vizard wrote an article on this topic.

Of course with todays oils many people aren’t interested in anything flat tappet, but with nitrating and good oil they can work well for a fraction of the cost. Especially when the valve events are mild such as a street use vehicle.

 

[Scooterwrench]

Hindsight being 20/20, should have just gone with a small, tight lash solid roller using a step nose roller camshaft ground for the solid roller lifters. Then used the solid roller lifters that drop in place of the hydraulic lifters. I have honestly been tired of hydraulic lifters for 15 years myself. Solid lifters can hold adjustment for a ton of miles without issue.

Have you ever done a lifter leakdown test. Something I've done just by hand using a phillips screwdriver to see how quickly the plunger leaks down(lifter has to be filled with oil). Guess you could get more scientific by setting the lifter up in a drill press and hanging a weight on the feed handle then timing how long it takes for the lifter to bleed down.
What about running Rhoads anti pump ups?

I used to recommend 10,000 mile re-adjustments for solid lifters in Harleys.