kdurg

The last few days the C4S has been behaving strangely....

During hard acceleration in 2nd, 3rd, 4th gears between 3500-4500 rpms the car will literally surge power and then DROP 200-300 rpms while my foot is on throttle. After this dip, it will regain power....but it sounds and feels very wrong.

Yes, the car is securely in gear. No, my foot is nowhere near the clutch.

Again my foot is on the gas while this is happening....it almost feels like something is slipping and causing this drop or gap in power.

Has anyone experienced this ? Or can anyone suggest any insights to the cause ?? Many TIA !!!!!

kkim

Clutch starting to slip, maybe? Purely a guess.

If so, that could be a blessing in disguise... (LWF).

Steve Weiner-Rennsport Systems

Hi Keith:

First,,...an RPM drop while accelerating is not a clutch problem,....RPM's go UP when then clutch begins to slip.

An RPM drop like yours is usually fuel or ignition related. It can also be an intermittent electrical connection somewhere.

I would ask you how old the fuel filter, spark plugs, wires, caps, rotors are? How many miles on the engine?

Might also be a slipping distributor belt.

If those parts are all relatively fresh, then you might be experiencing some bad fuel, as well.

This type of troubleshooting requires a very systematic approach. Go through this list item-by-item to find the problem.

1) Check plugs, wires, caps & rotors

2) Pull the distributor caps to make certain that the rotors are still in phase. There are small marks on the top edge of the bodies that will line up when #1 is at TDC.

3) Check ALL engine compartment connectors. Any moisture or oxidation wil trigger this and its takes VERY little.

4) After the above is done and everyting is OK, you might be experiencing coil or ignitor failure.

5) If your fuel filter is more than 10K old, get a new one. Bad fuel will clog that up very quickly.

Please let me know what you find.

kdurg

Steve,

The car has 68k on it. 60k service done about 5 months ago. Plugs, wires, caps, rotors and belt, fuel filter were all replaced at this service.

I just got back minutes ago from another run. Definately a problem. The car has increasing revs but then drops a bit and picks up speed again.......While the revs are "surging" the car does NOT increase speed.

I will check engine compartment connectors in a sec. Could this also be a throttle cable or linkage problem ??

Really appreciate your response.....

kkim

Perhaps I read too much in Keith's initial post, but in his ref to "power surge" I took as RPM increase due to the clutch slipping and the drop in revs was the clutch "catching" and the engine coming back to the actual RPM the engine was supposed to be turning w/o clutch slippage.

Not to discount what Steve is suggesting, but have you tried the low (4th or 5th) gear full throttle test to see if indeed the clutch is the problem? Quick and easy way to rule it out immediately and completely.

kdurg

Kelly,

Yes, the revs do increase but the car does not respond with additional power, the rpms dip 200-300 and then the car picks up speed again.

I have not tried this 4th/5th gear test you refer to.....what is it ???

kkim

Keith,

From an earlier thread w/ John D. replying...


Next higher meaning if you are in 3rd, shift to 4th. The idea is to load the engine w/ lots of power to see if it will cause the clutch disc to slip. If it slips the revs will increase, but the car's speed will not. If it doesn't slip, the car will pick up speed proprtionately to the engine revs.

HTH... good luck!

Steve Weiner-Rennsport Systems

Keith:

It doesn't sound like a throttle linkage issue unless the pedal feels sticky to you.

I'd do the clutch test and see if its slipping in the higher (4th-5th-6th) gears.

At 68K, you are "in the window" for a clutch change. If that turns out to be the case, I'd think about the RS LWF package.

kkim

Steve,
From a totally different perspective, I see Keith recently changed out his pedals...

https://rennlist.com/forums/993-forum/186940-does-anyone-have-an-oem-accelerator-pedal.html

Is there any outside chance that his changing the pedals out could somehow be the source of his problem? I know it sounds unrelated, but from my work experience when we encounter a problem, we always go back and see if the work just previous has any type of bearing to the present problem. Like I said, a long shot, but you would be the one to know if he somehow did something to upset the cart.

kdurg

Kelly,

Haven't swapped out the accelerator pedal just yet.....although I checked around the pedal this morning hoping to find debris or something wedged in that would be the culprit...no luck.

kkim

Keith,

Have you tried the "clutch slip" test yet?

kdurg

No, rain and sleet here now. Should be clear in a day or two though..

kkim

Ah, yes... inclement weather... forgot about that. Sorry.