Shedluv

Ok, I've had a 928 for about a year, and after doing a lot of reading, and it getting really cold for the first time, I've got a few questions. BTW, I did a search and didn't seem to get an answer I needed.

Here's the car:

1982 US model 928 - 3 speed AT

#1) Fuel mileage. The car gets horrible fuel mileage, even for a large V8. After reading about some users gas mileage it got me thinking. I'm getting about 13-14 mpg on the highway (60-70) going very easy on the throttle. In town and letting my g/f drive the car, the mileage goes down in the single digits. This is not from smokey burnouts and racing the like, just normal stop and go with the occasional fast acceleration.

#2) Low end power. I realize that these are high rpm engines, but at low RPM the car just doesn't pull at all. I can't even smoke the tires (take foot off brake, mash the pedal) unless its a little slippery. Not that I need that as a requirement, but I think that it should be able to. Now on WOT acceleration, after reaching about 3500-4000 RPM the car takes off like a rocket. For a comparison, I have a STOCK 98 S10 V6 that will outrun the 928 off the line up to about 40-45 MPG. I have no complaints at all about the high end power, just thought there should be a little more low end torque.

#3) Fuel filter stuck and wrong #. In regards to the above problem I replaced the plugs (not too bad) and noticed a slight increase in power and economy, but not much. The exhaust note did change slightly and I'm not sure why. I thought that maybe the fuel filter could be a problem, so I went to replace that too. I got a replacement WIX filter that did not fit. It was the right size, but the connectors on the ends were too small. I could not get the current filter completely off (got the pass side off, but not the driver's) as it appears to be stuck really good. My filter has the same number as the recommended replacement, but ends in .04 instead of .00. Also after this "attempted" maintenance I got a small fuel leak at the back of the car (like 1 drip every 5 minutes) but the filter and fittings are dry. Could I maybe have knocked something loose in trying to get the old one off? Could this be a loose check valve.

#4) When the car is filled with gas, it is reluctant to start at the station. Also I get a strong gas smell when it is full. It used to leak when full and parked on a hill, but I just figured that it was leaking out of the overflow.

The timing belt was replaced right before I purchased the car (little over a year -- have receipt) and the car has ran the same since I purchased it so these problems are not new (other than the leak). Am I expecting too much of my 928, or is there something wrong. I am fairly mechanically inclined but major disassembly is something that I'm interested in. Could this be a vacuum problem? I can think of several vacuum related systems that are slightly acting up. Those are:

Door locks -- when unlocking the driver's door, the pass door doesn't. Then when start the car the door's either both lock, or both unlock, seems to alternate.

Heater hose valve -- the valve under the air cleaner that allows the warm water to flow into the heater core no longer functions. In the summer I zip-tied it closed, now its open in the winter.

Flappy door in center vent doesn't not operate.

Most of the electrical problems in the car I have found and fixed easily and I've narrowed it down that its not them. Do I need to take the car to a professional and have the timing/ingition/fuel injectors checke, or is there something I can do to diagnose the problem. I have a local shop that works on Porsches, MB's, and a lot of other European cars, but their shop rate is roughly double that of most shops around here and they go way over on estimation (spark plugs estimated at 1.33 hours I did it in 45 min myself the first time). Just trying to get some ideas on what to do, or if the car is "just that way". Thank you for your time in reading this long post and your replies.

Sean79 5spd

You have described the performance and common problems of the average older 928 perfectly.

- Gas Mileage is about right.
- This is a heavy car, tough to spin the wheels on a stock 82
- 22 year old fittings are often hard to undo
- There is a hose between filler neck and main part of fuel tank,this often rots out
- Heater valves often fail
- vacuum and electrical problems are common on the older models

Good luck and have fun
Sean

Lizard928

I get WAY better gas mileage in my 86.5 32V 5.0L V8, I dont think that the L-jetronic should be that bad, it definatly sounds like you have some vacuum issues, as per the off the line, these cars are not off the line cars they have very tall gear ratios if you want an off the line machin, you need a different car, this is meant for running around the country roads at a very high paced speed, or flying down a long section of highway at speed

Jim bailey - 928 International

Shed ..... your engine is a 4.474 liter or 273 cubic inches , it is a SMALL V-8 . It is also NOT a High RPM engine it makes peak torque at 3,600 RPM horsepower at 5,500 . Your car weighs about 3,300 lbs which is heavy for a Porsche BUT pretty light compared to half the stuff on the road today . Go find sixth tenths of a mile of clear road and see how long it takes to cover that distance......... it should be around 29 seconds or find a shop with a dynojet chassis dyno do a couple runs and POST them here . I do not think your car is running right ........that is easy to say determining what might be wrong ....not so easy

Warren928

Sounds like a candidate for the roots supercharger system.

The 3 speed auto with 200+ horsepower is not going to be a rocket off the line. But you take my 86' AT, and even with LSD Ive been able to take off like a raped ape and leave burnouts. I would imagine the older CIS system is not as efficient as the new Jetronic, but a vacuum leak is likely affecting it. Id definatley check into that fuel smell problem. Are you overfilling the tank? that would make problems

Lizard928

Jim dont the 82 have a 4.7L? and L jetronic?
or am I missing something

Shedluv

It is a 4.4 L engine. Yes I know that is small for a V8, but having friends with trucks and big blocks getting better gas mileage than me made me wonder. I realize it will not "rocket" off the line, but in a stop-light to stop-light type race, my mom smoked me in her Lumina (we didn't get above 50 mph) with 3.1 V6 and auto trans. Its a dead heat to about 50 with my S10 (4.3V6, 5 spd, 100k miles), now anything above that and it pulls hard to 110 (that's all I've had it to -- public roads). And by high RPM engine, I meant that it has most of its power and torque up near the top of the rev-range, not a low RPM torquey engine. I don't need an "off the line" car, I just thought this would be a little more than it is.

Jim, I'll do the run when I get a chance this weekend. Going on a two hour trip and I should be able to find some nice straight stretch with little traffic. What speed should I hit at the end of the 0.6 -- I'm estimating about 120 from what the math would say.

Sean -- I hope the fuel filter is not 22 years old on this car, or has not been replaced since it was new, if so that would explain a lot of the problems with the car. I'm going to my uncle's this weekend with it and he has a larger garage with more tools than I do so we'll try to at least loosen the filter so that I could get it off later.

The power problems sound a lot like what other users have said about the 32V motor and the flappy valve not working, but I was pretty sure that was only on the 32V version, not the older 16V versions.

Thank you all for your replies and I appreciate any more ideas you can give me.

Randy V

Quite a shopping list you've got there, Lawrence.

I'll recommend that if you want comprehensive discussions on any particular issue that you enter on-going forum discussions on issues that you have a vested interest in, rather than lurking and compiling a list like this.

We're here to help, but this is a community of folks with the 928 as a common interest. What we are not is a drive-thru answer-your-questions service.

So, if you plan on keeping your 928 for awhile, you'll probably stop in here on a regular basis. If so, get to know the people here and post an occasional question.

We'll be here long enough to help you get all your 928 problems sorted out - eventually.

Jim bailey - 928 International

You might start your diagnosis with a compression check that tells a lot about the engine , if one bank is much lower than the other then the camshaft timing is probably off . If any are much below 100 PSI that cylinder is not going to run very well . Next confirm that all 8 injectors are clicking . Check the ignition timing (vacuum line unhook) it should be about 23 degrees at 3,000 RPM , 31 at 6,000 . With the vacuum hooked up check the advance at several different engine speeds write it down and go back and double check each one to see if it is consistent . Look at the spark plugs you remove for the compression test IF THEY all are fouled with carbon or just one or two .................................

mark kibort

Jims right here, as usual, but I will add that my 4.7 got up to 22mph, and often 20mph on a straight level road at 75mph ave.

sounds like you may have a fuel rich situation. cause??

plugs changed, cap and rotor changed?

timing? i thought the 82s were around 20 degrees , 3k, vacuum disconnect. (i know the 84s were in this range)
also, max timing should be in the 38 degree range with it connected 3kplus rpm.

oil , a good 20-50 weight

sounds like you have your work cut out for you .

MK

hacker-pschorr

Welcome to Rennlist!

Once you get your running problems sorted out, the exhaust on these cars are awefull. The stock manifolds can be swapped out with a newer style (can't remember what year) and the rest of the exhaust cleaned up for a few more horses. Not to mentions a 20+ CAT may not be flowing very well anymore.

2nd note. I checked out your web pics. Were those taken at the Douglas County Fair Grounds? Memories...........I grew up in Lawrence, KS. Who's the blonde?

Take care!

Jim bailey - 928 International

Kibort was correct on the timing I was remebering CIS ???? or was it a CRS problem ? thanks Mark K

GlenL

Lot's of stuff that might be wrong with your car. Should get better mileage and have more performance.

If I were you I'd:

Look for gas leaks by pulling the black cap (about 5" across) under the carpet in back and looking from under the car.

Pull the belt covers and make sure the cams are aligned right.

Sniff the exhaust for rich smell.

Get the filter off and check the fittings. The filter is supposed to have brass fittings with it. Someone might have improvised something different, but those lines and the flarenuts on them should be stock.

Look for vacuum leaks due to old, cracked hoses.

See if throttle is opening all the way.

Check spark timing.

karl ruiter

My '82 gets about 20 if I behave. Starts instantly in all conditions. Nice power all over the band. Screams at the top but will pull away from the curb in 5th. I use sticky tires because I dont want them to break loose so I dont know about that, but I can tell you that in 150K miles I have never thought I needed more power. I pulled out the automatic locks(which are electrical on this year) because they were doing what yours are. There are a bunch of (12mm?) vent hoses around the fuel tank that tend to crack when they get old and will leak a little when the tank is full or you are parked on a hill. Some are easy to fix and some are hard...just have to look it over. The only times I've had any trouble with how it ran was when I had some vacume leaks from cracked hoses around the intake. Oh, and once I had a bad plug wire. The wires are pretty expensive so you might want to have somebody put a scope on them rather than shotgunning it.

Shedluv

Thanks again for all of the replies.

I changed the plugs about 2 weeks ago. The old plugs looked ok, slight white discoloration on all plugs, not fouled at all. I did have a slight "red" tint to the discoloration on one of them (2nd back, driver's side). I put in new ones, gapped at 0.028, the old ones were gapped at 0.038 but I figured that was from wear. I'll look for a procedure on the cap and rotor and see if that's something I can tackle. I'll probably have to take it in to get the timing checked as I'm not real familiar with working on that. I do get a small puff of white smoke when doing a full "burp" of the throttle up to like 4k rpm when sitting in park. I'm going to tackle the fuel system this weekend and inspect all the hoses I can from the top or bottom and also check all of the fittings to see if I can find the leak and replace the filter.

Thank you all and I'll post more after the weekend.