I think I killed my engine

[Ctrout]

Well, I think I finally went and did some major damage to my engine. I have been chasing down vacuum leaks for a while because I thought I was running lean and I had a few other minor irritations with the way the motor was running. I had replaced all of the hoses and lines except for the fat ones between the plenum and intake runners. There was really no perceptible improvement. I had the car out for a spin on Saturday and it started to occasionally lose power. I wouould be driving along and all of a sudden it was like my rev limiter was kicking in. When I accelerate, I go through some major dead spots and the car surges badly. I thought I may have dropped a valve seat but when I did a search, it left me still wondering. It acts like an electrical problem but I suck at troubleshooting circuits so I'm ready to call it quits and move on to a 911 targa instead of my current 914 "project car". I've been kind of shopping anyway. Anybody need a 74 1.8l 914 cheap? Kind of a bummer after 2 years of very dependable fun.

[Scrappy]

Depends on where it is and what your definition of "cheap" is.

It is not an unsolvable problem.

[Ctrout]

Through a bit more troubleshooting and a minor electrical shock I have found that my #3 injector is not firing. The plug certainly is Anyway, when I was replacing the manifold gaskets, I noticed that the #3 injector had a bad insulator on the tip so I swapped it out with what I had thought was a good injector. I started the car and pulled the wire to #3 injector and there was no change in idle. when I pulled the plug wire at #3 Only hurts for a second. anyway, the engine stumbles when I tap the throttle and if I try to rev, it pops through through the AFM. I'm glad I have a spare.

[Ctrout]

Just swapped AFM and it runs perfectly. Why when I pulled the #3 injector did the idle not change before? Does the AFM control the injectors? When I pulled the other injectors, the car would stall. I don't get it.

[Ctrout]

And after more tinkering, I am convinced that I still have a vacuum leak somewhere. I can put my hand over the intake snorkel and the motor will not stall. I think I can hear a slight hiss from somewhere but can't for the life of me find it. I have changed every vac line, intake runner hoses, intake runner gaskets, fuel injector seals, oil filler box cork gasket. What could I have possibly missed? I'm really beginning to lose hope in ever getting this thing fixed. It runs extremely well compared to a week ago before this fiasco started though.

[RandyLok]

Take the air cleaner off and put your hand right over the throttle body at an idle. If that doesn't kill it...

Maybe there's a crack in the plenum?

Double check the hoses that connect to the plenum below the throttle body... maybe pull one off at a time and block with your thumb to make sure there isn't a leak further upstream (for example, a stuck AAR could feed extra air even if the hoses are good - but if you pull the hose and block it you'll rule out that tap).

[Dave at Pelican Parts]

The rubber boot from the air flow meter to the throttle body. It loves to crack down in the accordion pleats. You may be able to fix it with your favorite type of rubber goop. Someone on the Other Board fixed his up with the rubber paint you dip tool handles in, if I recall correctly!

--DD

[Ctrout]

I ruled out the plenum when I removed and cleaned/inspected it. While the intake was apart I also scrubbed the intake elbow with mineral spirits and then gave it two coats of tool handle dip so I don't think that's it either. I guess it's time to invest in a good stethiscope. Also, how do you check for a leak by covering the intake at the throttle body? I don't think the car will even start without the AFM installed will it?

[jim912928]

I agree with dave...check the big rubber piece the AFM plugs into (that big curvy thing). Mine had cracks within the accordian part..cant see them unless you bend it.