Engine "stumbles" over 2500 rpm

[Geoffrey]

Hey Gang,

    I drove Stella to work today since it was sunny and 78.

I got off the highway after about 25 miles and started on the last “surface street mile” to the office. All of the sudden the engine would stumble at about 2500-3000 rpms and drop power, than go back to 2500-3000 rpms again , drop power etc.. Any Idea what this could be? I re routed the pcv hose recently, could be a vacuum leak maybe? Any suggestions? I have another 8 hrs at work today, so I think I’ll be spending my free time researching 🙁

    Thanks,

              Geoff

[James Cochran]

Geoff,

How’s your fuel pump? I had a similar problem and it turned out to be my fuel pump could not provide enough fuel to the carb bowl. Ran fine at idle, but the higher fuel demand was too much for the old pump. Might be worth checking the fuel system.

James

[Scott A Chynoweth]

Geoff,I’ll jump in with the easy stuff first.Clogged fuel filter,weak fuel pump,cracked or wet distibutor cap,bad wires,causing spark to jump.Ignition control module going bad.And lastley timing belt jumped a tooth.Hope it gets you back home,my guess would be the timing belt.

[Geoffrey]

phew! I hope so too…. Thanks for the tips, I hope it’s an easy fix!

[Geoffrey]

I just started it in the parking lot and let it get to running temp. I could not replicate the issue. I simply refit the pcv hose again. I hope that gets me home so I can check the rest.

   Where do I point the timing light to check timing?

[Dan Rosa]

geoff104  my 2 cents the filter and fuel pump in my cars did the same thing, both my camaro and TD did it I had to change the filter in both and the trouble went away a cheep fix and quick I hope it is simple like mine        Dan

[John McDermon]

Geoff,

My PVC valve (the plastic elbow) was badly cracked and I was having similar issues with both a surging idle and occassional momentary loss of power at 2000-3000 rpm.  Replaced the PVC valve (along with the cracked plastic elbow) and it immediately smoothed out and ran like it should.  Replacement cost was about $2.

Good luck.  And let us know what it turns out to be.

 

 

Hawk52140091.6965509259

[Geoffrey]

Thanks Guys! I will replace the fuel filter, pcv set-up and I think the timing is off too…. It still runs kinda funky. I cant see the notches on the pulley to check the timing. I may need to remove some body panels. Hopefully not!

[Scott A Chynoweth]

I hope the timming comes back where it belongs,if not the belt jumped a tooth.

[James Cochran]

Remember what happened to Ringo . It is tough to see the notches on the pulley, but you may be able without removing anything, just twist around, like a pretzel. I steel wooled the pulley with the timing marks to clean it up and took a silver paint pen and marked the one that needed to show in the timing light. The timing belt cover on mine was very easy to remove to inspect the belt. I have seen some engines with the cover off all the time, but I would rather have it on.

[Geoffrey]

Thanks for the tip James!

[Geoffrey]

So, I re-timed the engine. I looked at the Mustang II manual and they suggested 6 degrees advanced. I ended up setting it to 10 degrees advanced and re-adjusted the mixture/idle speed.

   Wow!!! there is nothing as satisfying as new found Horsepower!! The difference in performance was amazing. First gear whips my head back and I’m not even done burning rubber by the time I need to shift into 2nd with a solid chirp in 3rd! Fun fun fun. You would be hard pressed to be able to tell I’m only running 4 cyl based on the sound or the performance..

   I promptly took her for a ride in the cactus laced desert mountain roads, and I’m still smiling a day later. Thanks for the tips,

                Geoff

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