308QV smooth acceleration??

It should be very smooth. What is happening? Bucking?

A thing I find remarkable about CIS is how the car just pulls smoothly at any rpm. It's a car you can slowly let the clutch pedal out from a standstill without gas and the car doesn't stall. I would have expected CIS to be quite a crude system, but the reality is that it's performance is excellent.

 

I haven't had mine a long time, but the one word I would use to describe the motor/ acceleration is smooth. Certainly not fast, but smooth and it sings above 4500 rpm . No hesitation whatsoever. There are a lot of facets to the fuel system, did you change everything? The throttle cable could very well be sticking a little, it is >30 years old. Good luck!

 

First off, I am no great diagnostcian. Some of the more experienced hands are sure to chime in.

I'd say though if it feels like something is sticking, something probably is. I would first suspect your throttle cable but the metering plate in the CIS unit itself probably can stick too.

The whole system is mechanically and hydraulically controlled (with gasoline as the hydraulic fluid) so is pretty simple and completely analog.

 

Sounds like the throttle cable is getting caught somewhere. I had a similar problem. Cable was lubed at both ends and is fine now.

 

Is it the acceleration in engine revving that is not smooth or the gas pedal that isn't smooth?
Because if it is the pedal, you don't have to have the engine running to feel how rough the pedal is.

 

Try the actual throttle plate. They build up with carbon, especially around the shaft, and it doesn't operate smoothly. Mine had actually stuck open it got so bad. Also check if your idle switch is operating properly, listen for the "click" when opening the throttle off idle. This can be done with the engine off.

 

I have been feeling this, too, since I got my '85 QV. Pretty much everything was original, so I've been assuming it is a sticky throttle cable or pedal assembly. It feels like there's a hitch in the acceleration just after I get off the line unless I increase significantly the rate of pedal pressure relative to clutch release. My mind immediately goes to fuel delivery, but I just replaced the Bosch TPS w a brand new one and the car came back from a major service and fuel system optimization by Francisco at FastCars, so I circle back to the mechanicals of the pedal/cable....

Beau LeBlanc

 

I've had the problem described. The fix was to pull the floor mat away from the gas pedal, it was touching it barely and causing it to shudder, stay revved when decelerating.

 

With the engine off is the accelerator pedal feel smooth?

 

The other thing you may want to investigate is the throttle mechanism itself. I had the same symptoms described by the OP with my 328 and the problem was solved by cleaning and re-greasing the articulating portions of the throttle mechanism. My primary problem was with the the lever pin (#35 in the diagram) on which the throttle control lever (#33 in the diagram) articulates. You don't see it well in the diagram, but over that lever pin is a metal bushing with grooves which, when greased, allows the throttle control lever to move freely over the lever pin which secures to the throttle housing. Upon disassembly I found very little grease left on that bushing and the grease that remained was rock hard. The first photo shows what the throttle looked like when I first removed it from the car. The second photo shows the lever pin, bushing, and throttle control lever disassembled and cleaned. The third photo shows everything back together. I hope this helps
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It wasn't the sticky pedal or cable. I took the car out and played with the symptoms a bunch. Here's what I can best describe it as:

If I leave a stop with anything less than decidedly aggressive clutch release/throttle application, then the throttle rise up to about 4,000 rpm will happen slowly and with seemingly no control of my own. If I put the throttle to pedal to 50% or more, the engine still revs slowly with no direct correlation to how quickly or how much I opened the throttle. If I needed all of a sudden to accelerate faster, I am totally sol. Sometimes during this rise time, I get a backfire or two. Then, all of a sudden, the engine responds and I have control again. It feels like I bogged it, but I can't have because I made a nice smooth transition from clutch to throttle without slipping, dumping, or missing the friction point at all.


Beau

 

Beau, I sent you a PM a month ago, did you get it?

 

Seems to me the plunjer in fuel distributor is sticky...

There is an intresting article how to clean the plunjer...

http://www.cis-jetronic.com/public_doc/07.3-0997-06.pdf

Guido

 

Mine acted like this when the distributor was on the way out on one bank. I also had fueling problems at the same time though.

 

I think you need to see a Bosch specialist. the one thing that I don't think is happening is that the FI plunger is getting stuck that would be pretty hard to believe and indicate there are other issues. so I would refrain from playing with the plunger... I would check for air leaks, and or if your check valve on the fuel pump is good. also check the relay protection fuse in the right hand side trunk - its under the carpet held on with 4 bolts.

t My experience has been its either electrical or air leak... rarely an actual physical FI problem. again to be sure get some one trained in Bosch Kjetronic Lambda.

 

Could be worth to to take a look at the ignition side also. I had some hesitation on low gears and low rews on my -85 Euro QV. Did all the throttle stuff and also changed the injectors, still the same. Looked inside the distributors and someone had managed to break the rear bank center connector cole in 45 degrees angle! Lots of sparks going in wrong places. New distributor caps and rotors from SP and no more hesitation.