engine cuts out

[yousaidpoo]

i've got a 1974 1.8 and whenever i rev the engine about about 4000-4200 rpm, it starts to cut out. it starts to feel like its bucking, and it does it through all the gears. i know for a fact its not the clutch. i'm thinking it may be that the throttle is dirty or has some gunk on it and isnt letting enough air through to allow the engine to rev above about 4k. i'm going to take it out and clean it either today or tomorrow so that may fix it.

what other things are most likely to cause this to happen?

[silver2.0]

I think I may know your problem, becuase I just got done fixing mine. It is the throttle position sensor. It has 20 small swithches that must be made at different throttle positions, and it will cut out on you in the area that is defective. It is a small black sensor located at the top of your throttle body. It has a slot that allows you to postion the switch exactly right, when reinstalling the switch. Hope this works, it sounds just like the condition I experienced. Let us know!

Tony

[BURN-BROS]

Fuel volume/pressure?

[pbanders]

If it's a 1.8, it doesn't have the same TPS that the D-Jet has, which has the 20 "clicks" for acceleration enhancement.

Cut-out's in all gears at a specific engine speed sounds like an ignition problem to me first, and an FI problem second. I'd check through the entire ignition system. The newest 914 is now about 28 years old, and I'd wager that many of them are still on their first distributor. Worn points plates, broken mechanical advance, and wobbly shafts are very common.

[yousaidpoo]

if it is an ignition problem, would it be worth it to go ahead and upgrade to an electronic ignition kit?

[Dave at Pelican Parts]

IMHO, any excuse to ditch the points is a good one. I really don't like points--they're far too fussy, and they take a whole lot of abuse for something as delicate and hard to adjust as they are.

--DD

[914GT]

Dave, I had to chuckle a little reading your post. I owned my old '68 Chevelle for about 25 years when I decided to dump the points and switch over to a Mallory Unilite system. It ran fine but no earthshaking improvement in performance. About a year ago (Mallory in there after about 4-5 years of occasional driving) it wouldn't start. Discovered the ignition module was blown, and a new one was $100. Went back to a $5 points kit.

I'll never know what took out the output transistor, maybe it failed on its own or a voltage spike. However one thing to consider in upgrading to electronic ignition is the compatibility to the old mechanical voltage regulators. Those things can spike and that might take out your ignition.

I just bought a $200 Accel distributor for my 914 V8 project, hopefully I'm safe with the alternator with its solid-state voltage regulator.

[Dave Bell]

Check the Air Flow meter for sticking.

To little fuel at higher RPM or spark is screwing up.

If the engine does this in all gears... I suppose you can make it happen in the garage while you are in neutral.

Get a buddy to rev the engine while you check a few things

1) Check fuel pressure... make sure you have enough

2) Put a timing light on one of the spark plug leads... if your spark is cutting out badly, you should be able to see in indication of that on the timing light. I still use points to trigger and electronic ignition on my 1.8L. If I haven't checked them in a while, the car will start to stumble sometimes when the points block has worn down and the gap is getting to small forcing some missing.

3) Check your AFM for sticking points and lubricate the hinge.
I had an AFM on my 1.8L that would occasionally stick in the open position and then flood the motor when the RPM's went down. With your condition, you could be having a sticking point part way open that limits injector open time causing you to go super lean at high RPM's and lose power.

- Dave

[yousaidpoo]

I figured out the problem(s):

1) The AFM was getting snagged at about half way open.

2) There was some dried gunk in the throttle body that limited airflow and made it tough to open the throttle all the way.

3) There was some crud on the inside of the distributor cap (dont know how it got there) on the little plates that the spark plug wires connect to. This meant not enough spark

Problem is all fixed now Now its time to fix the other stuff on the car. See post entitled "cant control my hose." for details

thanks for everybody's help

[yousaidpoo]

dave, you pretty much hit the nail right on the head, you had this kind of problem before?

[Dave at Pelican Parts]

OK, now you've found out the "what". Now time to find the "why"...

The crud on the cap is likely metal from the terminals inside the cap and the terminal on the rotor. This is why you replace caps and rotors periodically--even when they stay in good shape, the electrical contacts wear and the material moves around a bit.

The most pressing question to me--why does the AFM get stuck partway open? One of the least-happy causes of that is a backfire can warp the flap just a little bit... Or it could just be dirt/crud. See if you can clean everything up and get the AFM so that the flap moves nicely again.

--DD