3.2 - Throttle occasionally hesitates below 3k

TheSt|G · 06-08-2015, 06:15 AM

Occasionally in my '85 3.2 the throttle pauses/dips while applying gas, only to pick up again a half second later. The issue only seems to happen below 3,000 rpm and only when the car is warmed up. May be unrelated, but she also just completely died when going around a slow 2nd gear bend, but fired right back up without complaint. The stall was also very smooth, as if one had just flicked a light switch.

The hesitations have me thinking the AFM wiper might need to be adjusted to a new track, but the random stalling out seems to be a complicating variable. Thoughts?

CCM911 · 06-08-2015, 09:10 AM

If memory serves me correct, you replaced the plugs and filters less than a year ago, correct? Mine has started to do the same thing, so I am leaning towards the fuel pump. Why else would there be that small delay? I also need to change my fuel filter.

TheSt|G · 06-08-2015, 09:59 AM

Quote:

Originally Posted by CCM911

If memory serves me correct, you replaced the plugs and filters less than a year ago, correct? Mine has started to do the same thing, so I am leaning towards the fuel pump. Why else would there be that small delay? I also need to change my fuel filter.

Also possible, though it does seem odd that it's only below 3k rpm.

On the fuel side of things, swapped the filter last year and put in some Techron this spring.

MrBonus · 06-08-2015, 10:12 AM

I've had this issue since I bought my car. Changed the fuel filter, plugs, wires, and air filter and it improved. Replaced the alternator and the hesitation was even less noticeable but it still persists just a bit and only below 3000 RPMs. I wonder if it's a vacuum leak somewhere.

TheSt|G · 10:52 AM

Quote:

Originally Posted by MrBonus

I've had this issue since I bought my car. Changed the fuel filter, plugs, wires, and air filter and it improved. Replaced the alternator and the hesitation was even less noticeable but it still persists just a bit and only below 3000 RPMs. I wonder if it's a vacuum leak somewhere.

Fuel filter, plugs, wires, and air filter have all been replaced within the last year.

It's not so much a hesitation as during a consistant throttle application, the power cuts, and then kicks back on again a half second later. I think Chris is on to something with the fuel pump, as I now remember hearing it buzz fairly loudly the other day.

Len 911 · Len 911's Garage

I also have an 85, I just went thru the same issues as you. The fuel pump was going up and then did, I put a new pump from our host and runs so much smoother in lower rpms. I would start with the fuel pump, Plus its a good piece of mind knowing it is new. I went up and had to have it towed home.
If it was loud the other day it is the pump for sure, Mine did the same thing. The wife asked why there was a loud noise in the front, I told her fuel pump going up two days later it did.

Not hard at all to do
Good luck

TheSt|G · 06-08-2015, 11:24 AM

Quote:

Originally Posted by Len 911

I also have an 85, I just went thru the same issues as you. The fuel pump was going up and then did, I put a new pump from our host and runs so much smoother in lower rpms. I would start with the fuel pump, Plus its a good piece of mind knowing it is new. I went up and had to have it towed home.
If it was loud the other day it is the pump for sure, Mine did the same thing. The wife asked why there was a loud noise in the front, I told her fuel pump going up two days later it did.

Not hard at all to do
Good luck

Yup, pricing it out now. Does not seem at all bad. ~$350 for the Porsche OE pump, new brackets, new hardware, new mounts, and new clamps.

Cevan · 06-08-2015, 11:26 AM

I had a similar issue with very slight bucking at little load around 2500-3000 RPMs. I did two things that seemed to fix the issue. I removed my AFM, cleaned the track and contacts and lowered the contact arm so it ran on a new track. While the right side of the air box was removed, I checked most of the 12 intake bolts. Two were very loose. There was at least one I simply couldn't get to.

DRACO A5OG · DRACO A5OG's Garage

Take care on the OEM PAG pump, make sure it does not buzz out of the box. Take note of the 2 year warranty.

Mine started to buzz after a year, thinking no way it is bad since it is OEM. waited to long and tried to replace but warranty ran out.

MrBonus · 06-08-2015, 11:32 AM

Quote:

Originally Posted by TheSt|G

Fuel filter, plugs, wires, and air filter have all been replaced within the last year.

It's not so much a hesitation as during a consistant throttle application, the power cuts, and then kicks back on again a half second later. I think Chris is on to something with the fuel pump, as I now remember hearing it buzz fairly loudly the other day.

Describes my problem as well. Group fuel pump replacement day?

Len 911 · Len 911's Garage

Order a new rubber hose. The one from the tank to the inlet side also. Very easy job but you will get some gas down your arm....

TheSt|G · 11:49 AM

Quote:

Originally Posted by Cevan

I had a similar issue with very slight bucking at little load around 2500-3000 RPMs. I did two things that seemed to fix the issue. I removed my AFM, cleaned the track and contacts and lowered the contact arm so it ran on a new track. While the right side of the air box was removed, I checked most of the 12 intake bolts. Two were very loose. There was at least one I simply couldn't get to.

That's on the plan. Doing the sound pad while I'm in there.

Quote:

Originally Posted by DRACO A5OG

Take care on the OEM PAG pump, make sure it does not buzz out of the box. Take note of the 2 year warranty.

Mine started to buzz after a year, thinking no way it is bad since it is OEM. waited to long and tried to replace but warranty ran out.

What a pain in the ass. Noted.

Quote:

Originally Posted by MrBonus

Describes my problem as well. Group fuel pump replacement day?

Welcome to stop in when my parts get here.

Quote:

Originally Posted by Len 911

Order a new rubber hose. The one from the tank to the inlet side also. Very easy job but you will get some gas down your arm....

PET seems to have no part number for that. Any ideas?

*Edit* Found it on Pelican, added to order. Thanks for the heads up.

Len 911 · Len 911's Garage

I called pelican and asked them .told them what pump I was getting and they new. .I think it was 12mm rubber fuel line...

TheSt|G · 06-08-2015, 11:50 AM

Quote:

Originally Posted by Len 911

I called pelican and asked them .told them what pump I was getting and they new. .I think it was 12mm rubber fuel line...

Yup, just found it in the catalog and sent them a memo to add it to the order with another hose clamp.

doublebuffle · doublebuffle's Garage

I had the throttle cut in/out at WOT. I found this while T/S'ing:

http://forums.pelicanparts.com/porsche-911-technical-forum/867226-1984-carrera-bucks-pops-when-cruising-medium-throttle.html

Was not the problem. It turns plugs/wires/cap/rotor/and fuel filter ended up resolving the issue. There is a procedure for testing the Throttle position sensor, can't remember whether it was in Bentley or on the forum though...