Hanging idle: Solved!

[Quantum TD]

I thought I might post this in this section. If I'm in the wrong area, please feel free to move it mods. I just wanted to share an experience.

I've got a 1982 Caddy with a 1986 Golf 1.6 engine in it. I didn't have a history on the motor that I swapped into it, but I started it on the floor of my garage and it ran great. Compression test showed great compression too.

So, I put it in, and replaced just about every seal on the motor/trans, including the seals in the pump.

It's been running fine since I resurrected the truck, but I've had a really bad hanging idle problem. I've never played with the fuel or idle screws, because it always idled perfectly when warm. It only hung, when I came off of acceleration. I'd be sitting at a stop light and it would hang for about 20sec-3 minutes. Sometimes, it would never come down.

After reading some posts to the effect, I went ahead and rebuilt my injectors. Before doing so, I pop tested them to see what they looked like. 3 out of 4 looked ok (break pressure and pattern), but one popped WAAAY too early, and if you slowly worked up the pressure, it would piss out sideways in a stream that would work around in a circle, before the injector finally opened fully at a below-spec pressure.

Anyway, since rebuilind the injectors (new "cheap-0" Bosch Indian injector nozzles), and setting the pressure, NO MORE hanging idle.

So, I guess the bottom line is. In my opinion, if you have a hanging idle problem, you may want to look to your injectors first, before you start playing with the pump.

A similar story happened to a customer of mine. His truck ran fine, but had a leaking injection pump. I resealed the pump, and then his idle started to hang breifly after accelerations. I swapped in some Bosch rebuilt injectors from a parts dealer. It still hung. It turns out, 3 out of the 4 injectors were leaking and one was pining badly (nice work Bosch!!!). I rebuilt him another set, and ate the crummy Bosch rebuilds. My rebuilt injectors solved the hanging idle, and gave his truck more power. Even better, had I rebuilt the set from the start, I would have made more money on the deal, since nozzles are cheap (like $32 a set), versus BOSCH rebuilts which list for like $45-65 each!

It seems like I've read alot of posts recently about people having thier pumps resealed, only to have hanging idle issues afterwards. They generally assume that it has something to do with the reseal. I think it may have more to do with the pump putting out more pressure (or residual pressure) than before, and making worn injectors dribble, thus leaving a hanging idle.

Just some food for thought...