2008 HM CRE F450XI Logo
Anonymous Posted on Nov 10, 2008

Un usual rpm spikes

When im cruising along at 55 mph 3500 rpms for my 1983 CRE F450XI my rpms will spike if i give it any gas past 4000 rpms. the rpms spike about 500 and the power drops significantly. it feels exactly like someone reached over and pulled my clutch as i was riding. if i continue to give it gas after the spike the rpms keep going up but i dont go any faster just keep going the same speed. if im going uphill and give it gas it does the same thing and the bike slows down if i slowly roll off the throtlle after it has spiked you can feel the bike almost re-engage and the rpms go down about 500 and you feel the power come back but if you give it any more gas it jumps right back into this high rpm powerless stage. it has more effect in the 4th and 5th gears. i might also add that the rear cylinder coughs when it idles and i havent looked into its carb yet. i also just put on straight pipes instead of the baffled ones but it didnt affect the front cylinder. the book also speaks of a mixture control valve that may go bad.

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Anonymous

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  • Posted on Nov 10, 2008
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Joined: Aug 07, 2008
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At a guess.... Your clutch is slipping. Higher gears and increased drag at hiway speeds put the most torque through the clutch and it sounds like that's when the plates start to slip. When you back off the plates grab again until the load over powers the plates again. But that's just a inter-guess through a computer screen...... ,,

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Related Questions:

0helpful
2answers

The rpms seem higher on this vehicle than I am use to seeing, cruising at 80mph the car is hitting 4000rmps. Is this normal for this vehicle?

there is not enough specif details available to be able to be close to exact But I will give an example that you can compare
in a manual transmission with a diff ratio of 3.909 and in 5th gear the rpms for 79 mph is 3200 rpms
the difference between gears is around 250 rpms so if you try to correlate the differences if it was in 4th gear the rpms would be around 3750 rpms so I suspect that the over drive section of the transmission is not engaging ( assuming that it is auto transmission)
so to answer your question , I am saying that it is too high in rpms for that speed and I suspect that the od is not being engaged as the rpms at 80mph I would be looking at around 3200-3500 rpms depending on the diff ratio
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Why is my rpm runs high at 55 mphr at 3500

Your transmission is not shifting make sure it is in D, if automatic
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Problem accelerating after 40 rpms shoot up

You have a failed transaxle

The rpm flairs,that is a dead give away

You may have a worn out & clogged exhaust converter, adding to the problem, but the trans is gone, if the rpm flairs & after 45, you it doesn't run half decent
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Along with the other poest if i smack the steering wheel while driving on the freeway or or just doing 50 mph,the rpm will rev up or if i tap the break while driving the same thing will accur what can...

year make and model would be a good start???And what do you mean by smack on the steering wheel? You mean turn sharp? or actually smack the wheel, which I do often. Need more info dude
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95 T-bird LX, V-8 hesitates after a soft stop, some turns, after small climb and after a bump or crossing tracks; try to accelerate the rpms whip up past 3-4 car is not moving, what's up with that

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