74 914 1.8

[dimmer]

Hi;
I hope you can give me some ideas on my problem.

I have a stock 74 914 with a 1.8 litre with L-jetronic fuel injection.

The car has just been tuned up, but the problem predated the tune up. I have checked the idle, dwell and timing. As I rev the car the dwell does not move. It is set at 45 degrees. I have also checked the valve clearance. The engine was completly rebuilt with less than 5000 miles on it.

The car runs great at idle or when I rev it up in the driveway

The problem is when I am driving the car. If I suddenly put the clutch in it idles at about 1400 rpms. If I come to a stop and then put in the clutch at the last minute the car idles back at 900 rpms. It does not always do the 1400 rpm stunt, but I can always get it to idle at 900 if I put the clutch in at the last minute.

At 1400 rpms when I take drive away I get valve chatter if the rpms go below 2000 or if I accerate hard.

Any thoughts would be appreciated.

Thanks

[jamcleod]

do you still have the deceleration valve connected in the FI system? i think the decel valve is supposed to gradually lower the rpm's to lessen emissions so my first thought is it's operating the way it's supposed to.

[philinjax]

Your clutch cable and accelerator cable are interferring with one another. Remove the accel. cable from the pedal assembly and reroute it so that it doesn't touch the clutch cable.
Phil

[dimmer]

Thanks for your imput
I do not beleive it is the accelerator cable as I checked the throttle body and it is fully released.
I tried disconnecting the small hose on the decel valve and there is no change.
The valve chatter really concerns me, I am going to check the valves again tonight to ensure they are up to spec.

[jamcleod]

your valve chatter is not "pinging" is it? probably not since the 1.8 has a paltry 7.6:1 compression ratio and runs on regular. the reason i ask is that i would have thought valve noise would be all the time not just on accel. again, i'm a wanna-be mechanic so hopefully there are more informed answers to come. live on 1.8's (i have a 74 1.8 also :>) )

[Dave at Pelican Parts]

My old 1.8 pinged on acceleration, particularly when the engine was fully warmed up and when I put in a middling-high amount of throttle in a high gear at low-ish RPMs.

An air leak can cause that, as an overly-lean mixture will preignite easier.

900-1400 RPM out of gear is a very very small change in throttle position. I kind of doubt you'd notice it just by looking. Try checking the throttle and clutch cables, as Phil noted. This is a pretty common problem in 914s.

--DD

[scg]

Plug the hose from the decel valve to the air manifold and see if that stops it.