Motor hits wall at 5000RPM (power loss)

[1SICKGT]

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CAR: 1991 5.0 mostly stock except for mods listed in sig.

PROBLEM: I took my car for a boot today and noticed a wee bit of a problem. At 5000RPM on my Autometer tach(and 5500RPM on my stocker), my car feels like it's hitting a rev limiter, because it wont allow my car to exceed 5000RPM(5500RPM on stock tach). It sounds like the fuel is still being delivered because you can hear the exhaust popping as it would when fuel hits the hot headers.

I though it might have been a problem with my soft touch rev limiter on my 6Al so I disconnected it. Still the same problem.

My question is, where should I start with this one? TFI? bypass the 6AL? all input appreciated!

Thanks!

EDIT: tried bypassing the 6Al, still the same problem. Could this be a valve float issue?

 

[Ranchero5.0]

First try regapping the plugs to about .040". Worked wonders on my friends '88 TC 5.0 conversion with an A trim. Thing fell on it's face at 4500rpm acting like it was popping out the TB, but it was loss of spark.

He replaced the plugs and had them gapped to .054 with a crane ignition.

Jamie

 

[Aliate X]

wow I didnt know stock tach's could be off by that much.

 

[Deleted member 87397]

Try advancing your timing a little too.

 

[90mustangGT]

A weak coil, module or pickup on/in distributer going bad, bad plugs, could be many things. Even a weak fuel pump, it's hard to say.

 

[CrazyCobra]

Does it do this in all gears? I had what sounds like the same problem, after my 6AL died and had only the coil, it would miss only in first gear and sometimes second. As mentioned above I regapped the plugs to .035" and everything was fine. I had to regap 8000kms later, when the problem reoccured.
I would also start here as it's free, however with a 6AL you should be able to run close to .060" gap . maybe its somthing else.

 

[CrazyCobra]

wow I didnt know stock tach's could be off by that much.

My stock tach reads 6500rpm when my autometer shift light comes on at 5800rpm, rev limiter is passed 7000rpm, this really impresses the ricers because they don't know any better(around here anyways) .

 

[1SICKGT]

The fuel pump is a brand new 255lph, and the coil is a brand new MSD unit. I will look into the plug gap, but last I remember it was .035

Crazycobra: yes, it does it in all gears.

Thanks for the replys guys

 

[BlooDReigN]

A buddy of mine had the same problem with his 5.0 except it did it at like 3500 RPM. Turns out it was the distributor. He went and got a new one for the junk yard and all was well.

 

[1SICKGT]

to the top!

 

[1SICKGT]

Anybody else have input!?

 

[ECU5.0]

the stock cam doesnt make power much past 5k anyways. it could also be valve float....i know my car runs great and pulls hard all the way to redline but at like 4k rpms it breaks up like crazy because of valve float.

just a few things to add