[T3] Bad day at the (FI) office

Daniel Nohejl d.nohejl at gmail.com
Tue Mar 15 06:58:00 PDT 2016


Thanks for all the replies. I’ll respond generally since there’s enough to add that replying one by one would flood everybody’s inbox….

Yes, we’re on our 4th motor in this car: the original, the rebuild of that, an interim motor to replace the failed rebuild, and now a brand new one. Each of these motors has had varying combinations of FI components and each has presented its own issues, the worst being over the summer on the interim motor when it’d randomly cut out, shut down, and leave us or me on the side of the road. That seemed to have been eliminated by replacing a frayed TS2 and an MPS that didn’t hold vacuum. 

The recent symptoms are akin to that, but the motor doesn’t cut out, it just hiccups and almost stalls like it would with a vacuum leak. I’m sure anyone with FI is familiar with a hunt at idle, that big lope up and then down in a rhythmic cycle. On the AFR gauge, you can see lean peaks and rich valleys as it cycles. However, the new symptom isn’t rhythmic like that…..it’s intermittent and it doesn’t surge. It’ll idle at normal speed and then almost cut out at which point the AFR shows richness before rebounding to “normal”. It seemed to be aggravated by the headlights being on but it also happens with them off, just not as often. It also seems to happen under load which would explain the bucking I experienced yesterday. 

I only paid attention to the hissing noise you hear in the video because I was wondering about a vac leak based on the symptoms.  In my mind, there’s always a bit of a non-localized hiss which I’ve attributed to the sound of the generator, the fuel pressure regulator, and air moving around the engine bay combining to make a noise but I figured I’d listen around anyway. At the same time, if there was such a major air leak that you could hear it loudly on video, then I imagine there’d be a big hunt at idle or worse. Then again, I’m getting like 15 mpg and obviously running rich with sometimes weak throttle response so who knows?

We’ve been chasing FI problems on and off from the moment we got the car as a roller in June of 2012, so we’re coming up on 4 years now. I can’t help wondering if daily driving FI is a bad idea. Everyone says it should be “set it and forget it” reliable but that’s never been true for us for more than relatively brief periods. I’ve put 1100 miles on it in less than a month and I wonder if in driving it like this, we’re pushing the “issue threshold” of these old components. In other words, maybe those who drive a lot less see fewer problems simply because they drive less and ask less of their 47 year old electronics? Of course I say all of this after having to wake up 45 minutes earlier, triple my commute time, and all of that on account of the car!

Oh, and yes, there is still a gas heater in place, but I’ve disabled it and the booster fan in the engine compartment. The fan gave me issues for a while as it would randomly turn on when I’d shut a door or close the rear hatch and I couldn’t track down the cause. Once, I didn’t realize it had gone on after I left the car and it drained the battery overnight. 

At the very least, I can check that the distributor hasn’t moved and that the timing hasn’t changed. Other than that, what else to look at/for?





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