Well, This is Odd (Engine Tuning Issue?), Changed batteries, and something strange happened. Options

[JDW914]

I'm not sure what's going on here, but I'm hoping somebody here will.

I've been driving my car ('74 2.0 all original engine and FI) for a few years now, I did some tuning last summer, and it's been running great since. But, having it out only once a week at most, this winter the battery had started to show signs of wearing out - the car was getting hard to start and often needed charging - so last week I bought a new battery and installed it.

Initially, this seemed to work great: I turned the key, the car started immediately, and it idled perfectly at 1200rpm. However, as soon as I touched the gas, the engine revved to 3000 and stayed there for about 20 seconds. Upon experimentation, it seemed that the engine would retain both power and speed of any throttle position for a ~20s period after the throttle was returned to idle. I was able to alleviate this to some extent by turning the idle-mixture adjustment to maximum and opening the idle bypass by 5 turns, but it still acts weird.

When I set the idle mixture to do anything besides flood the rpm down, the engine stays at 1500 rpm even with the idle bypass closed all the way and the AAV closed off.

My instinct is that it's a vacuum leak, but there's not a whistle to be hard or lose hose to be seen. Could it be (I hope not) something to do with the FI system?

[dralf]

I has been quite some time since I have been on this web site, but it is just like riding a bike... one never forgets and it is always fun. Reading about your problem, I have a suggestion for something you may try. Perhaps changing your battery has slightly affected voltage throughout the FI system and thus your throttle position sensor is now acting up. I think generally a worn/dirty throttle position sensor causes hesitation, but perhaps it can cause a lag as would be the case with a worn dimmer switch on a lamp.

It is an easy thing to remove, clean and re-install... I eventually replaced mine with a brand new one before they became a bit pricey. In my case throttle response was noticeably better with the new unit..God luck with your problem...