Contour Enthusiasts Group Archives Forums Modifications Zetec Maintenance Found my culprit for the recurring P0171 code!

96 GL 2.0 ZETEC AT 132,000 mi.
After two years of on & off tinkering on my daughters Tour, trying all logically suggested methods with no definate fix, I accidentally stumbled across my vacuum leak.

I recently overhauled the braking system due to poor pedal performance (Brake Fade) and found By accident a 5 in silicone vacuum line to the Power brake booster with a sizeable hole burned thru.

If you remove the vacuum line to the brake booster and follow this down underneath the intake manifold past the inline check valve you will find the tube.

A possible theory was a gradual slow loss of vacuum over time causing P0171 and eventually the hole became big enough to affect the braking system.

All I can say is after MAF & EGR checks and all the suggestions posted here I had no joy. The CEL would always return P0171 with an intermittent rough idle. I replaced the hose with a 15/32 (11.9mm) rubber pcv hose and the car runs better, brakes better then it ever has.

Of course it didn't hurt to change the timing belt, WP, pulleys and lower radiator hose last week.

If you are like me and have no joy with the P0171 code check this vacuum line, it could be leaking.

I've gotten a 171 as a pending code (among other codes, but the 171 is the current one). Intermittent rough idle as well, so I'm sure it's a leak some where, just finding it may be the hard thing. I though it could be from around my TB, but I don't really think it's that, though I'm gonna seal it up. Can you give me a better idea of where the hole in the hose was? Thanks.

Follow the vacuum tube from the brake booster to below the intake manifold. The line is in 3 pieces, all pieces are hard (silicone ABS type plastic) the middle piece has a slight bend below the intake runner. This is where I located the hole. I believe through rubbing over time the hole caused a vacuum leak to cause a P0171 fault and eventually it became big enough to cause the loss of brake booster efficiency. I replaced the bad section with 15/32 PCV hose and the cost was $2.89, the car is running like a top now with no codes pending after 2 days. It is tough to hear because of the TB being right above this area. Feel the length of the tube (engine off) and if you feel a rough area on the tube it could be rubbing as well. HTH

Thanks, I'll definitely check it out.

I'm beginning to suspect my creeping lameness may be a vacuum leak, because it affects mainly lower revs. But it doesn't seem to affect idle, mostly it takes effect during acceleration.

Little off topic. When ya'll with ATXs do a brake stand aka power brake, how high does your car rev? And I thought if I kept give it gas it would break loose from the brakes and roll but it just hangs at ~2500rpm. This can't be good for the powertrain.

i have the p171 code as well. i was told it is my o2 sencer. but i have a rough idle bad gas mileage loss of power. i cant put my finger on it.

Well it has been 1 week and no CEL, the ZETEC is running great and the braking system is fine too. That 3in. section of tube was surely the problem for PO171. Had the hole not opened up large enough to affect the brake booster's performance I'd still be scratching my head. No mods done on this auto, 100% stock, before you go replacing sensors, poke around for the not so obvious vacuum lines.

Always wise to state car info. If you have a '95, 171 code is different than P0171. Former is O2 related, latter is lean code.

I too have been having problems with a recurring P0171 code for the last bit. I recently replaced the ATX in my 1998 Zetec Contour. Upon restarting it I could not get it to idle very smoothly. I tracked it down to a cracked fitting male end on the power brake booster hose where it enters the manifold After moving the car and having no power assist on the brakes. The nipple end had broken off inside the intake . If you ever exchange a tranny and leave the engine in the car and drop the tranny out the bottom as Haynes says, be sure to remove the Power brake booster hose at the power brake booster. Anyway, I repaired the hose fitting by inserting a piece of copper tubing inside to support it and epoxying the end back to the hose. Unknown to me, I had dropped out a soft rubber bushing while removing the broken off piece from the intake. I re-inserted the fitting without hte rubber sealing bushing. Now I am getting a sluggish part throttle start and a hotter running engine when at part throttle. I am also getting a CE light with P0171 code when it does this. Tomorrow I am going to remove the hose and replace the seal and fitting. BTW, a 180 degree T-stat cured the temp on "A" in normal after 140,000 miles. I had accepted it as normal for it to do this.So if your 'tour Zetec is running high side of normal, try that first. Hardly ever hear the fans now.

Charlie