porsche928guy

The 85 has developed a bit of a problem. When I got the car the A/F gauge would cycle between lean and what (I think) Carl said was 12.3:1. It would hunt for an idle a little bit before settling down but has gotten much worse.

The other day I was driving it down the road and noticed the A/F gauge was all the way to lean. It would come up every now and again but never got to 14.7 and it is steady with no movement. I've checked all the vacuum hoses I can find and all are connected, checked the lines at the FPRs for gas and nothing, redid the intake boots with silicon hose and t-bolt clamps as they were popping off...but still no dice.

The car will idle pretty steady out of gear but once put into gear it will hunt up and down for an idle and will even die once in a while. It seems to run fine going down the road. I haven't driven the car under these circumstances except to get it home for fear of causing some damage...any troubleshooting ideas?

Mrmerlin

is the O2 sensor new?? Or is it connected? Can you give more specs on the car your working on, what was the last thing you fixed?

porsche928guy

Mrmerlin...thanks for the reply. I haven't really fixed anything. I haven't done much to the car as I just bought it and the problem with the idle was somewhat existing when I bought it...it has just gotten worse and the A/F gauge thing just started. I noticed the boots on the intake kept coming loose so I replaced those with better clamps and silicon hose thinking that wouldn't hurt and hoping it'd help but it didn't. O2 sensor is not new but is connected. Fuel filter is new.

I'm just looking for a few possible starting points to narrow it down. From reading here is seems like a few possibilities could be:

MAF
FPRs
O2 sensor
vac. leak

I'm sure there are plenty others...just needing a good starting point.

John Speake

Start by setting up idle CO and idle speed according to the WSM.

Mike Frye

I think this part may be a clue. Usually people have problems while idling anytime (including in neutral). Isn't there a vacuum connection that goes back to the auto tranny? Maybe you should start there, if there's a problem with that line, then being in gear could exacerbate it, no?

I'm not very familiar with the autos, but vacuum seems to be the most likely cause for rough idle.

PorKen

Could it be the (spark is blowing out)?

I would try (adjusting the MAF). Failing that, if it hasn't been rebuilt, it likely needs to be.