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does a 99 5.7 thunderbolt 4 ignition system have a rev limiter?

S

stang32

Regular Contributor
i can't find any posts regarding this issue. hope to clarrify if ther is a problem or not.
it seems that the ignition breaks down when goosing the throttle in gear over 4500, i had a timing light hooked up reading the rpms and over 4500 the rpms got all scattered.
 
No rev limiter on TB-IV

Either Cap, rotor or pickup (sensor).
Also see if wires are good. Spark jump can occur on bad wires at higher rpm

Typically when a timing module fails, (Not all the time) the timing will not advance past ~ 2400 rpm
 
Just re-read post title,
A '99 would not have a TB-IV
It would have a TB-V and most likely a knock sensor.

Double check you info ......
 
correction, it is a 96, not 99. fat fingers syndrome,
there is no knock sensor and there is no knock module. just the 1 amplifier mounted on the distributor and no , there is no harness plug unused where a knock module may be missing from.
 
Last edited:
OK,
I did some research on 1990's to 2000 TB IV and TB V
Service manual 17 1993-1997
Service Manual 24-1998-2001

Everything I read thru showed the following.

Both manuals show if TB V with knock module and require to jumper wire for base timing then there are two additional timing modes built in.

1. MBT - mean best timing
2. Over rev control - if engine spec says 4800-5000 max rpm the Over rev will kick in at 5100 and reset when rpm is reduced to a "preset" lower rpm the rev limiter will "reset". They use an example of 4750 rpm as a "reset"

In manual 17 {1993-1997} there is a cross over of TB IV and TB V.

It does not specify when that occurred but the original TB V modules started to be mounted to the distributor with no knock module and was the same basic function as the TB-IV. No jumper needed to adjust base timing and no MBT or Rev control.

What is clear is all references to rev control show knock sensor piggy backed on timing module.

So I do not know first hand how to identify what you have other than part number on timing module.

Manual 24 (1998-2001) does not show any reference to the TB V ignition system without the Knock sensor. All show Knock module and have MBT and rev control.

So I would look up the part number on module to confirm what it is and what TB V it is.


that's all I have.

Maybe someone has more first hand experience with trouble shooting this.
 
Last edited:
Rev limiter/no rev limiter.... This issue has nothing to do with a rev limiter.... Start with an OEM tune up, change the pick up (Especially if it only has 2 wires) disconnect the helm tach at the coil and retest....
 
Docksidemarineservices said:
Rev limiter/no rev limiter.... This issue has nothing to do with a rev limiter.... Start with an OEM tune up, change the pick up (Especially if it only has 2 wires) disconnect the helm tach at the coil and retest....
Click to expand...

I agree,
I was answering the question on rev limiter timing module.

Virtually all carbed small blocks rpm range is 4400-4800 and newer models may spec out at 5000.
If he is not able to get passed 4500 its not a rev limit issue.
 
ok, i retested with another tach and at exactly 4800rpms, it breaks down. it has a full ignition tune up including sensor and coil.
i think i was chasing a ghost that was not there.
there is no id mark on the module ( mounted on the dizzy)
other than part #'s it does not say tbIV or TB V like the module usually found mounted to the manifold
 
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