Violent shuddering at half throttle

[Devin]

The last two days when I am getting up into the post 3500 RPM range in gear the power will cut out for a fraction of a second. I don't remember if the actual RPM drop or not but the whole car will slow down, then speed up, slow down, speed up, and so on. It's almost whiplash inducing. There is no idiot light coming on. What should I check? It almost seems like fuel or spark is cutting out for a fraction of a second and so the engine stops making power. I reved my engine in neutral and the butterflies open. Where should I start looking?

This sucks cause it's really hard to keep the car under 3500 RPM.

 

[SHO GoDz 89]

Sounds like bucking.
Cam/crank sensor
DIS?

Either one of those things can give those symptoms.
Doubt it is a fuel issue, I'd put my money on cam/crank sensors though.

If you end up stalling, check your tach and see where it is when it stalls.

 

[Devin]

Bucking, that's it. I couldn't think of the correct word. Hopefully it's not the CKS because it has been replaced. The cam sensor is original though. Would either of those throw a code? I'm not sure how to troubleshoot a sensor issue.

 

[SHO GoDz 89]

Sometimes they don't throw codes until they completely fail. Mine didn't throw a code when my CKP went.
Also, if your CKP was changed (like mine was) and the wire loom wasn't actually bolted to the water pump then it can come lose and rub up against your pulley...that's how my new CKP went. It shorted out the wires.

I got the same "bucking" when it failed, the CPS I think would just give you starting issues since it has mostly to do with injector synchronization on start up.
Check your DIS too. Check your grounds, and if you have a spare DIS then replace it. Do everything you can before spending money. Best advice I could give you is to try and eliminate all other possibilities.

 

[oneqwicksho]

Sounds like crank sensor going south or inproper clearance on instalation of cps. another thing would try double check fuel pressure and clean maf just to elimanate thoes two

But sounds like cps

 

[Devin]

CKS = crankshaft and CPS = camshaft, right?

No issues on startup. I had developed the problem a few months back sometimes when clutch in and the RPMs drop, they will drop all the way down and stall. Only happens on clutch in and is spotty. I went out on a test drive after my wife lost her keys (had to go home to give her spares) just a few minutes ago and I didn't have any issues until I was in second up in the upper part of the band (5-6K) It started bucking and acceleration is just flat from 4K and up. Shifted into third and got up to 60 MPH. Clutch in and stall. I down shifted and compression started (since I was still moving). Definitely seems like a sensor issue.

So it sounds like you guys thing it might be spark then, since that's what the DIS controls.

 

[pitaSHO]

Sounds like the same thing that happened to a friend's car. It was the cam sensor. The car would drive fine for the first ten minutes or so and then would buck like a ****** off bronco. If it was the crank sensor the car would just stall and not re-start.

Chris K.

 

[SuperHO]

as already been stated, your cam sensor has committed suicide. replace it, say a few words, and move on with life, and remember, if you need help grieving the loss of your cam sensor, SHOforum's here for you,

 

[Devin]

Thanks! I believe it's the only sensor that has not been replaced since the refresh.

Anyway, I will be picking up a sensor this evening. Does it require seperate gaskets?

 

[pitaSHO]

No gaskets. You might check to see if any oil is leaking from that cam seal. If it is, I would replace the rear cam seal or the leak could damage the new cam sensor...

The cam sensor is just the plug and two 5.5mm screws. If you do the cam seal, the aluminum shroud thing has to come off, too. That's two 8mm bolts.

 

[N3FOL]

I may go ahead and replace my cam sensor, since it has been there for the last 100K miles and the car is bucking. Just ordered a cam sensor from Advance Auto for $36 bucks. It this ok to use or should I stick with Motorcraft?

 

[Devin]

I just used whatever was sent to me. I can't remember the brand but I know it isn't motorcraft.

 

[Devin]

As a followup, the CPS was definitely the problem. No problems with dying or bucking at all since I replaced it.

 

[walser]

this exact thing happened to me, cam sensor, and it did not throw any codes, i think i got it for about $30 at napa. i would start there amd it only takes like 15 min to swap