4.0L ohv startup rattle

[DangerangerHD]

1994 Mazda 4.0L rattles during first 1000 rpms. 142k miles. Has as long as can remember. Exhaust shop said there was a tick they could hear in the oil pan/bell housing area when I had them install a test pipe. I swear I can barely hear a tick while driving (only under load), maybe, or I'm imagining it lol. I'm running fresh mobile 1 10w/30 high millage and a can of liquimoly ceratec additive. Had the valve covers off yesterday and had zero sludge or carbon buildup as I recently did a 3 stage flush and replaced pushrods and rocker arms.

Does anyone else have a half second rattle noise immediately after startup?

Could it be a wrist pin, rod bearing?

 

[BlackBII]

If it goes away right after starting then it could be the starter motor. Sometimes the bendix drive will stick and the flywheel will spin the starter.

 

[RonD]

+1 on starter motor drive run on

My '94 4.0l is very high miles now, I use the "Clear Flooded Engine" software in the computer on cold starts now.

This pumps up oil pressure before the engine starts
All fuel injection computers have Clear Flooded Engine routine in the operating system.

Turn on Key
Press gas pedal down to the floor and hold it down all the way
With 0 RPMs and TPS(throttle position sensor) above 4.5volts computer enters Clear Flooded Engine routine
This turns off fuel injector pulses, spark stays on, with no fuel it will cause a No Start
Crank engine for a few seconds then let off on the gas pedal, injectors will start and so will engine.

See if rattle is less or goes away, indicating oil was draining out of the engine system while it is off, could just be from age and larger bearing gaps.

Oil filters should have backflow preventer valve built in to hold oil in the main passages when engine is off.
But since this has been happening, I assume over a few new oil filters, that's probably not the issue.


Just a heads up if you try the Clear Flooded Engine routine
If engine starts right up with gas pedal to the floor then you need to do the "Throttle Cable Mod"
Google: Ranger throttle cable mod

Your throttle cable has stretched so you no longer have Full Throttle, do the mod, very very easy, then try the Routine again

 

[DangerangerHD]

Thanks for the input guys! Filter does have anti drain back valve (mbl 1 gold). I've never thought of using the flooded engine system as an oil priming method but will have to give it a try, and of course the cable mod is the first thing I've done on all of my rangers because free power is the best hp!

 

[DangerangerHD]

Actually the starter hang up is beginning to make more sense because I've been fighting a high idle issue where on startup it jumps to 2500 rpm or higher them settles at about 1300rpm. I had the anti diesel screw backed all the way out and disconnected the iac and it would start and idle at about 500rpm.... But i don't remember the rattle! My guess is the starter gear cant disengage fast enough when it jumps to 2500.

Anybody have experience with modifying the iac gasket to limit idle due to Teflon throttle body coating deterioration?

 

[cp2295]

My 4.0 rattled on cold start, and then when it was hot it would rattle at 3000+ rpms when in gear and under very light load. When i rebuilt it all the rod journals were scored beyond machining and the bearings were down to the copper. Never blew up or rod knocked however. If i was you i'd hook up a mechanical oil pressure gauge and see what your readings are. I was 8 psi oil pressure..

I was in disbelief that the motor didnt blow up, a real testament to these things tougher than nails


Sent from my iPhone using Tapatalk

 

[cp2295]

+1 on starter motor drive run on

My '94 4.0l is very high miles now, I use the "Clear Flooded Engine" software in the computer on cold starts now.

This pumps up oil pressure before the engine starts
All fuel injection computers have Clear Flooded Engine routine in the operating system.

Turn on Key
Press gas pedal down to the floor and hold it down all the way
With 0 RPMs and TPS(throttle position sensor) above 4.5volts computer enters Clear Flooded Engine routine
This turns off fuel injector pulses, spark stays on, with no fuel it will cause a No Start
Crank engine for a few seconds then let off on the gas pedal, injectors will start and so will engine.

See if rattle is less or goes away, indicating oil was draining out of the engine system while it is off, could just be from age and larger bearing gaps.

Oil filters should have backflow preventer valve built in to hold oil in the main passages when engine is off.
But since this has been happening, I assume over a few new oil filters, that's probably not the issue.


Just a heads up if you try the Clear Flooded Engine routine
If engine starts right up with gas pedal to the floor then you need to do the "Throttle Cable Mod"
Google: Ranger throttle cable mod

Your throttle cable has stretched so you no longer have Full Throttle, do the mod, very very easy, then try the Routine again

I suggested an oil pressure gauge but this is much easier good call ron!


Sent from my iPhone using Tapatalk

 

[Mark56]

I need to do throttle hold down n crank on my 3.0....it ticks and misfires on
cold starts.....
That's why have to find out if the 98 4.0 from explorer will work computer n wiring ect n m.y 1999 ranger 4x4 xlt....

 

[2ndSS]

the oil priming thing is more of a band aid than a fix, could be a lifter bleeding down overnite , you need to distinquish if its a lower end rattle or a lifter type rattle.