rafrench

have 1987 928 s4 53k mi all orig near mint. Bought from my son as he became very frustrated after 3 shops could not find following problem. I'm hanging in there! When cold,surges until warm then smooths out although seems to run rich then when you shut off and let it sit for a few minutes it starts but stumbles badly and sometimes dies but starts back up. After pumping accelerator a no. of times after restart it smoothes out. After that it either runs ok or surges a little. Probably a coincidence but couple mos. ago put in new o2 sensor and it ran great untill now. It's up to it's old tricks again and is in it's 4th shop with no good news yet. Have done most obvious fixes: MAF(rebuilt),drainded gas,new fuel reg.,checked or replaced most electrical components, etc. Please help! Thanks, Russel

Randy V

You probably wanted to post this in the 928 tech forum:

https://rennlist.com/forums/928-forum-69/

rafrench

thanks, can I switch it without typing the whole thing again?

911SLOW

Moved to the 928 forum.

Landseer

Russel,
There are a lot of little things that can make them run poorly.
Only a 928-specific shop can efficiently sort it out.
Or guys here.
What is your location?

Be patient, you are in the right place.
Probably we need to see a few photographs of engine bay and fuse box.

87 coil wire nick will really mess-up running.
Also, wrong fitting wires.
Corrosion under the coil caps, visible with light and mirror, is another problem.
Vac leak, also under maf.


Also, bad grounds ( there are a few very specific ones, battery strap itself fails), also the engine electronics ground to the engine deep below the MAF at back of valle.

Generally, I'm finding that at this age/miles they need a thorough refresh of ancilliary wear parts and electrical for reliability sake.

Being as you are a new owner of 928S4, a few very important general things, though, deserve mention.

First is fuel lines. At 47psi, a crack in a rubber fuel line, which notoriously happen after somebody has had their hands in the engine bay, will burn your car to a crisp. There is a process for easily and inexpensively replacing all the engine bay fuel lines with new. Don't let the low miles cause you to overlook this.

Second is dropping bell housing cover, releasing flexplate tension on automatic cars and measuring crankshaft endplay. There is a design flaw with these cars that will cause the engine to drag internally and destroy itself -- all 32V automatic cars need to have the pressure released and then measurement made. There are inexpensive auxillary clamps to prevent progression. Search for flexplate measurement or TBF (thrust bearing failure) to find the right information and procedure. The right shop can do it inexpensively, but few have a clue.

Third is timing belt / water pump. Interference engine. 50K miles was the approximate recommended replacement interval. This one might have original belt and you could be on the edge of failure, especially if its stumbling and running poorly due to added stresses that will be on the belt in that situation.

Here is the absolute best news. These cars are very, very cool and reliable and strong. Core is bulletproof -- heavily built engine and trans. ALL the documentation on the cars is available, not hidden. So long as the thrust bearing is ok --- that car is going to serve you very well.

rafrench

thanks for great advice

WallyP

Go here http://members.rennlist.com/v1uhoh/underthe.htm and locate the fuel pressure dampeners (one front, one rear of the engine on the fuel rails) and the fuel pressure regulator (one on the rear). Each will have a small rubber vacuum line attached. Each has a fabric and rubber diaphragm with fuel pressure on one side and manifold vacuum on the other. A leak in a diaphragm can cause problems similar to yours. Pull the vacuum lines and check for any trace of fuel in the line. Any trace of fuel indicates the unit should be replaced.

rafrench

Do you guys have an owners manual for 1987s4? I appreciate your advice on my problem.

Rob Edwards

Link to all MY owner's manuals, generously provided by AO:

https://rennlist.com/forums/928-foru...al-online.html

1987:

https://docs.google.com/viewer?a=v&p...yYWFi&hl=en_US

rafrench

thx, but looking for actual manual

Speedtoys

Where are you? You could be a block away from an expert and we dont know it.

Whats in the manual that'll fix it?

docmirror

I'll toss something out.

Idle stabilizer valve. Although your car is low mileage, they do stick, and are affected by cold and hot because they sit right in the valley of the engine under the intake. Also, while you are in there, check for vacuum leaks. Very common problem as the rubber gets old and brittle, or cracked.

NoVector

I didn't check all the links. http://www.cannell.co.uk/Manuals.htm If this doesn't work, Google search. I forget which volume, but one has the diagnostic matrix--maybe 1 or 1a.

I'm with Wallly--easy to check. Tke the vacuum hose off the FPR and FPD, put your thumb on the hose and then see if it smells like gas. Good luck--don't give up!