HELP---Strange Engine Noise is very puzzling

[datzenmike]

The CAS is driven off the crank shaft. Maybe just wear on the mechanical parts.

[raythomas]

CAS? Crank Sensor?

Would replacing the sensor help?  Can they go bad or wear out?

If it's caused the timing to "move" electronically, and I adjusted it manually by turning the distributor,  Is it possible it could move again by itself?

Electronically I mean.

 

Thanks

Ray

[raythomas]

Is this what it looks like? So it's mounted in the distributor?

Ray

[raythomas]

I've got another little issue that I should have mentioned earlier but the "noise" problem sort of took center stage.

After I drive the truck for like 15  to 20 minutes then shut the engine off, about 8 out of 10 times it is really hard to start back.

It turns over fine but acts like its starved for fuel. I can put my foot on the gas and mash it to the floor and the truck will finally start.

Kind of like what you used to do to an old carburerated engine. Only this engine is FI so that throws me for a loop.

Do I need to start a fresh post on just the hard start issue, or run with it here?

 

Thanks
Ray

[datzenmike]

It may have something to do with the CAS timing so get a timing light and set the timing first. It may still be too advanced.

 

 

Yes that's the CAS. If it runs then it's working.

 

There's a wheel with 360 marks plus an outer ring with just 4 marks and a photo cell that reads them. The engine knows within one degree where the crank is and the four TDC points. 

[raythomas]

Well I borrowed a timing light from a buddy at work today.  Checked it and it seems to be slightly off. It didn't check at 10 degrees BTDC it checked closer to the Zero mark. Had the idle correct for a 5 speed manual and when I twist the distributor to 10 degrees BTDC which is factory the truck Pinged and knocked like crazy when I test drove it. In fact it was louder than the original knocking. I moved it back to right around zero degress BTDC and it drove fine. Shifted and pulled through the gears with no pinging or knocking. I even lugged it some in 3rd and 4th and still all was smooth and quiet. Anybody got any ideas why my timing seems to be running better 10 degrees off from factory? 

Thanks

Ray

 

P.S. I've included a small pic of what I'm talking about, just in case I'm thinking or explaining it wrong. According to the manual I should be

timed at the ORANGE mark, but the truck runs best at the BLUE mark.

Edited September 26, 2023 by raythomas

[datzenmike]

Pretty sure the timing for a Z24 is closer to zero. This is because of the dual plugs. With two ignition sources the fuel air mix burns faster so less timing is needed. If running single plug it would be more like 10 degrees. Check your timing specs. Probably 3 degrees BTDC

[raythomas]

Well that's some good news for once. Seems like my engine is close to factory settings and not pinging and clattering. 

Now we just gotta figure out why its hard to start back after driving for 15 to 20 minutes and shut down. 
Thanks

Ray

[Stoffregen Motorsports]

Check the timing all-in.

 

If there's a problem with the distributor (or CAS, or ECM, or even the TPS or AFM, heck even a temp switch) it can mess with the timing curve and cause issues. If there is a problem, and you reset your initial timing to within spec, the total timing may be off.

[datzenmike]

3 hours ago, raythomas said:

Well that's some good news for once. Seems like my engine is close to factory settings and not pinging and clattering. 

Now we just gotta figure out why its hard to start back after driving for 15 to 20 minutes and shut down. 
Thanks

Ray

 

Check valve lash. 0.012" for intake and exhaust.

[raythomas]

4 hours ago, datzenmike said:

 

Check valve lash. 0.012" for intake and exhaust.

 

I had already checked that and it's within spec.

THanks

Ray

[1001001SOS]

The web says obd1 started on the Hardbody in 87, If so you can try to read the codes off the ecu and see if the hot start issue shows up as something. 
 

The pinging you posted in the audio recording definitely sounds like pinging haha. I don’t know much about this engine but I would maybe check resistance on various sensors while it is warmed up and see if they are still in spec. Heat=Resistance and sometimes a warm engine is enough to make a weak electrical connection fail.

 

If it was a KA I’d say knock sensor and MAFS, I have had both cause this. If you messed with the wiring at all there is a warm start signal also that you might could check.

[raythomas]

9 hours ago, 1001001SOS said:

The web says obd1 started on the Hardbody in 87, If so you can try to read the codes off the ecu and see if the hot start issue shows up as something. 
 

The pinging you posted in the audio recording definitely sounds like pinging haha. I don’t know much about this engine but I would maybe check resistance on various sensors while it is warmed up and see if they are still in spec. Heat=Resistance and sometimes a warm engine is enough to make a weak electrical connection fail.

 

It is was a KA I’d say knock sensor and MAFS, I have had both cause this. If you messed with the wiring at all there is a warm start signal also that you might could check.

 

Man I wish it was that simple. When I got this truck the previous owner had used a "shade-tree" mechanic to do a bunch of work on it. It's had ALL the SMOG stuff disabled and removed so I'm sure if I checked codes this ECU would take a royal pewk . So there's that. 

Thanks

Ray

[datzenmike]

Depends what was removed. The timing and air fuel is regulated by the ECU with inputs from the engine sensors. Mixture and timing could be anywhere without them. Some failures force the ECU into 'limp home' mode an engine saving over rich condition.... maybe this has been circumvented by removal of smog equipment causing problems..  

[Stoffregen Motorsports]

Most of the "sensors" are designed to work in conjunction with each other. So if one is removed, it would definitely cause a problem. The MAF (or AFM), temp switch and TPS all send signals to the ECU which then adjusts air/fuel ration and timing.

[raythomas]

1 hour ago, Stoffregen Motorsports said:

Most of the "sensors" are designed to work in conjunction with each other. So if one is removed, it would definitely cause a problem. The MAF (or AFM), temp switch and TPS all send signals to the ECU which then adjusts air/fuel ration and timing.

 

So is it possible that the SMOG stuff is all taken off but these sensors you speak of are still working and doing what they are suppose to do? Reason I ask is this truck has been driven for years without any issues at all up until the pinging/clatter started. Could you define "LIMP" mode please? I'm assuming its just to get you home and not really for everyday driving?.....ie low power output?

 

Thanks
Ray

[datzenmike]

Limp Home mode:

 

The air fuel ratio in an EFI can vary widely under certain conditions including being dangerously lean which is detrimental to pistons and valves. Thus if certain error conditions happen, the ECU selects a preprogrammed safe overly rich condition. It's assumed the operator will notice the terrible gas mileage and investigate.

[raythomas]

23 minutes ago, datzenmike said:

Limp Home mode:

 

The air fuel ratio in an EFI can vary widely under certain conditions including being dangerously lean which is detrimental to pistons and valves. Thus if certain error conditions happen, the ECU selects a preprogrammed safe overly rich condition. It's assumed the operator will notice the terrible gas mileage and investigate.

 

 

Well this truck has plenty of power, doesn't foul spark plugs and gets right at 35 mpg. So I guess it's not limping.

Ray

[powderfinger]

12 minutes ago, raythomas said:

gets right at 35 mpg

come again?

[raythomas]

8 hours ago, powderfinger said:

come again?

 

Gets between 30 and 35 miles per gallon.

Ray

[powderfinger]

first i have ever heard of a z24 getting that kind of gas mileage 

[datzenmike]

Mid twenties for 2wd would be normal.

[1001001SOS]

Check out this thread, had some good things to check (clutch safety switch and battery terminal jankiness):

https://www.nissanforums.com/threads/hot-no-start-problem-on-86-5.168820/

 

Regarding getting 35mpg, how accurate is your speedo? Tire size?

[Stoffregen Motorsports]

23 hours ago, raythomas said:

 

So is it possible that the SMOG stuff is all taken off but these sensors you speak of are still working and doing what they are suppose to do? Reason I ask is this truck has been driven for years without any issues at all up until the pinging/clatter started. Could you define "LIMP" mode please? I'm assuming its just to get you home and not really for everyday driving?.....ie low power output?

 

Thanks
Ray

What smog devices did you remove? There's really only a couple on a Z motor. EGR and PCV. Some motors misbehave when the EGR is removed, but I don't think the Z is one of them. L motors certainly benefit from EGR delete.

 

It's more likely that something has either suddenly come out of adjustment or failed completely.

 

Limp mode usually throws a bunch of fuel in to help keep from burning the motor down. Doesn't sound like that's what is going on here. A bad sensor would probably put it into limp mode. It sounds more like something came out of adjustment.

 

Is there no diagnostic port on this thing? Even OBDI had a diag port.

[raythomas]

5 hours ago, Stoffregen Motorsports said:

What smog devices did you remove? There's really only a couple on a Z motor. EGR and PCV. Some motors misbehave when the EGR is removed, but I don't think the Z is one of them. L motors certainly benefit from EGR delete.

 

It's more likely that something has either suddenly come out of adjustment or failed completely.

 

Limp mode usually throws a bunch of fuel in to help keep from burning the motor down. Doesn't sound like that's what is going on here. A bad sensor would probably put it into limp mode. It sounds more like something came out of adjustment.

 

Is there no diagnostic port on this thing? Even OBDI had a diag port.

 

I have read there is a switch or dial you rotate or switch on the ECU under the passenger seat and then read the check engine light blinks. But I've never tried it simply because I figured with all the shadetree work done that it would be loaded with tons of codes just relating to that.  It did have a slow to start as in slow turning over years ago, but that was because the negative battery cable was loose. The problem I have now is it turns over fast it just seems like it isn't getting fuel or spark for some reason. It will usually start if I hold the throttle to the floor while its turning over. After a few seconds it will start sorta blubery for a few seconds and then it smooths out and runs fine. It has had this little quirk for a year of so and was doing it before the pinging / clatter had started. 

Thanks

Ray

Edited September 28, 2023 by raythomas