Peter Zimmermann

My '74 914 1.8 now starts well and idles pretty good. However, it refuses to smoothly accept throttle, instead of revving it bucks, shakes violently, sometimes even backfires in the exhaust.

My question, have any of you run across an issue like this that was caused by piston rings seized in their pistons? My compression ranges from a low of 108 to a high of 112. This might be too low across the board but I don't know/have a spec for what is acceptable. Also, when I did the valve adjustment I discovered a lot of condensation rust in the valve covers.

Thinking back on that rust I'm beginning to wonder if the piston rings are sufficiently stuck in their ring grooves to affect what's happening in the combustion chambers. In review, I have a perfect ignition system, a very good FI system with many new parts, and no air/vacuum leaks. I have not put Marvel Oil or an aerosol spray (like PB Blaster) into the combustion chambers.

Matt Romanowski

It's been a long time since my motor was stock, so I don't exactly remember, but I think my compression numbers were around 130-140 lbs. Do a leak down and you'll learn a lot more very quickly.

Trying to remember the fuel injection system - where does it have potentiameters? Does it have a tps? One for the maf? Are those putting out good signals?

Jay Gratton

Speaking of the TPS Matty, "did you get the TPS report? NO! I will send you another one."

Come one, name that movie!!!!!

Matt Romanowski

It's "did you get the memo?"

http://www.dailymotion.com/video/xhr...moy_shortfilms

Peter Zimmermann

HEY!!!

Just because you relented and told me that you will sell your basement boat anchor to me doesn't mean that you have Carte Blanche to be a thread hijacker!

Sheeeesh...

Jay Gratton

Sorry Pete! I am sorry for stealing your thunder. I feel since I can't offer and actual help I will at least bust people's ***** from time to time.

Matthew, thank you for clearing up my error.

Peter Zimmermann

Jay Gratton

I have done my job!

Peter Zimmermann

Good!

Now ship that boat anchor, I think my piston rings are rusted in place and reduced compression is preventing the engine from revving. I might as well build a 2.0 w/carbs if I'm going to build an engine!

ca993twin

Just poking my nose where it doesn't belong, but your symptoms sound more like ignition timing.

Peter Zimmermann

Poking is OK, actually it's welcome! I thought ignition timing as well, so much so that I again removed the distributor, took it completely apart, serviced/cleaned it to perfection, re-installed the distributor drive and put the whole thing back together (new coil, condenser, points, rotor & cap, dwell = 47).

One thing that puzzles me is that my timing light (a good quality, but old, SnapOn unit) kept shutting off, then coming back on, as I tried to rev the engine (on a 1.8 L-jet engine the timing is set at idle at 7.5 degrees BTDC) to see what the distributor advance was doing. I did not get back to that because I ordered a new spark plug wire set (just delivered) but haven't had time to install it and re-check timing again.

Matt Romanowski

Is the coil or points signal bad?

You should be really nice to Racing916 and get him to ship his good 1.8 out to you. Anything from him is going to be A+.

Peter Zimmermann

That is the $64,000 question! I had to create a new harness from the regulator board to the different engine points. I never thought to measure voltage from the board to the coil (with the engine running), but I did measure continuity, which was good. It's been really hot here (over 100F in my garage), so I haven't done anything in the last few days, but if you think that I'm getting a pulsing signal that could explain the on/off with the timing light, and the very bad off idle running.

The weather is supposed to be hot for another day, so I'm going to spray PB Blaster into the cylinders tomorrow, hopefully it'll reach the rings, and try to get the car running again on Friday morning. Voltmeter on the coil will be my priority.

Jay Gratton

Not a bad idea actually! That is Matt's good idea for the day, he is now closed for business.

Matt Romanowski

The day is still young, I'll come up with another good idea.