Bruno DeSousa

first off let me say im new to this site and i just bought my first porsche and im sure you guys are sick of hearing the same questions over and over.. but here i go anyways...1981 928 with 43k original miles. black with black leather 5 spd! its in sweet condition except for the way its running.. it was sitting for years and im trying to breath new life into it... the fuel pump/filter have been replaced.. new oil and filter.. new gas(93 octane) in tank and new plugs.... now excuse me if i sound like an idiot here... my car doesnt seem to have this WUR that everyone is complaining about on cold/warm issues BUT my car seems to have those symptoms...(starts and runs fine on cold startups then once warm it starts to run rough/hesitate under acceleration and also seems to be misfiring.. some white smoke out of the tail pipe..eventually it will just stall out and when i try to restart it, it doesnt want to fire until i throttle the gas pedal and also wont keep an idle the motor warms up.... since it is original 43k mile motor.. should i still be concerned with the diagrams in the fuel regulators? i suppose they could dry rot..also besides checking all the vacuum lines i did notice towards the rear of the engine on the passenger side under the airbox a 2 pronged sensor looking thing with t vacuum hoses coming out of it. one of the prongs was broken off, would this be my problem? also what else can i be testing or looking for? thanks in advance guys i hope to enjoy my journey! im located in connecticut.. if any guys are local and willing to come help in person let me know thanks, Bruno

Bruno DeSousa

first off let me say im new to this site and i just bought my first porsche and im sure you guys are sick of hearing the same questions over and over.. but here i go anyways...1981 928 with 43k original miles. black with black leather 5 spd! its in sweet condition except for the way its running.. it was sitting for years and im trying to breath new life into it... the fuel pump/filter have been replaced.. new oil and filter.. new gas(93 octane) in tank and new plugs.... now excuse me if i sound like an idiot here... my car doesnt seem to have this WUR that everyone is complaining about on cold/warm issues BUT my car seems to have those symptoms...(starts and runs fine on cold startups then once warm it starts to run rough/hesitate under acceleration and also seems to be misfiring.. some white smoke out of the tail pipe..eventually it will just stall out and when i try to restart it, it doesnt want to fire until i throttle the gas pedal and also wont keep an idle once the motor warms up.... since it is original 43k mile motor.. should i still be concerned with the diagrams in the fuel regulators? i suppose they could dry rot..also besides checking all the vacuum lines i did notice towards the rear of the engine on the passenger side under the airbox a 2 pronged sensor looking thing with two vacuum hoses coming out of it. one of the prongs was broken off, would this be my problem? also what else can i be testing or looking for? thanks in advance guys i hope to enjoy my journey! im located in connecticut.. if any guys are local and willing to come help in person let me know thanks, Bruno

granprixweiss928

that little two pronged thing is a vacuum switch that is heat-from-the-engine triggered.
If one of the lines is broke off them you have a vaccuum leak. I think this is for the evap system.

white smoke aint good, might be leaking coolant into the cylinders when warm.

have you checked compression when warm?

1981 engines have Bosch L-jet Fuel injection, so no WUR ( thats for CIS systems, 78-79)

Those fuel regulators are easy to check, pull the vacuum line off and if there is fluid coming out, then they are really failed, if there is fuel smell in the vacuum line or at the nipple, they they have also failed

do the tests for the thermotime switchm and coolant temp switch (located on top of the water bridge) and also, have you tried unplugging the 02 sensor and seeing how it behaves then

Mark

77tony

....

Bruno DeSousa

thanks mark! ill check compression tomorrow.. but it runs and sounds fine when i start it cold.. it smells rich. so i thought the white smoke was from running rich.. hard to believe 43k original mile motor to have bad rings or a coolant leak internal(head gaskets) hmm but ill check it out.. what should i do about the vacuum switch.. ill try to find one to buy and replace it. ill also check the regulators and see if they hold vacuum..if that doesnt work ill try unplugging the o2 to see if there is a reaction.. all the plug wires are firing so i think the dist is ok.. but ill take the cap off and check . thanks again for the tips. ill try to post some pics of the car soon

GregBBRD

Send the injectors out for cleaning.

Bruno DeSousa

haha thanx for the pic resize... hmm injectors clogged? even with only 43k miles?

hacker-pschorr

Welcome to the tank.

I merged your two threads together and copied the re-sized photos from Tony's post to your post so the large ones went away.

bureau13

I suspect cloggy injectors might be more due to sitting around than having high mileage. There's a pretty good chance you have a number of issues contributing to your problem. I did....I replaced the MAF, ignition wires, distributor caps and rotors, etc and all helped, but new injectors was the single biggest thing I did, and what finally got my car feeling right.

Bruno DeSousa

but the car runs very rich when i first start it.. so clogged injectors? im going to do some tests tomorrow afternoon.. compression/vacuum/fuel regulators/distributor/vacuum advance/wires... before i go ahead and pull the injectors if needed.

dr bob

You might want to share where you are so we can decide if it's a Euro car with CIS, or a US car with electronic injection. That changes the diagnostics a lot.

Cars that sit a long time with fuel in them suffer when tat fuel varnishes in the injection nozzles.

Often, what appears to be a rich condition on start-up is actually a lean condition causing misfire, that allows raw fuel to pass through the engine unburned. If there's no catalyst, you get some dark smoke at the same time. After the catalysts warms up, the raw fuel reacts there and you have overheated catalysts that will soon fail from that heat.

White smoke in an engine only after it's warmed up is frequently a sign of a headgasket or headgasket area failure. Cars sitting for extended periods with old coolant suffer from this a lot, as the aging coolant becomes more acidic with time. It eats the aluminum metal that supports the gasket. The 'white smoke' is steam. If there is actually coolant in the system, that smoke might have a sweet smell.

There are three basic things needed for the engine to run: Compression, spark at the right time, and fuel. Your diagnostic efforts will focus on those areas. The car was obviously stored a lot with the age and mileage, so you'll start off with new fluids (oil, coolant, transmission, and brake fluid) before you get very far.

Because of the age and storage, you'll test for fuel pressure with a fuel pressure gauge and adapter for the fuel rail cap. It's very likely that the injectors are at least partially clogged, but because of the difficulty of removal and diagnosis, you'll save that step. If you have good fuel pressure, move to ignition.

ASSuming this is a US car, the ignition includes all the standard stuff, plus... The primary ignition relies on a signal from a sensor in the distributor to tell the ignition when to fire. Signal passes through a green wire from distributor to ignition box, and the wire suffers with age. It's a shielded cable inside with unique connectors. Replacement with new is the best diagnostic method. After that, the spark-plug wires are solid core with resistors in the end pieces. You can buy just the wire sections and assemble them to your plug end pieces, or get a whole new set. Pay particular attention to firing order, detailed on the sticker on top of the radiator.

Compression testing isn't hard. You'll want to pull the fuel pump fuse and the ignition fuse, then all the plugs come out. Use a compression tester (free rental at most parts stores) in each cylinder to verify that the headgaskets are holding and there are no ring or valve leakage problems. Crank the engine with throttle wide open as you test.

Old cars have issues with aging and crcking fuel hoses, including the sections between the fuel rail and the injectors. When you talk to Roger for the manuals (see below...), get a set of new fuel lines at the same time. Old fuel lines too frequently leak and lead to annoying fires.

Old injectors almost always need at least a good cleaning. There are services that do this for you, just send them to the service and get them back in a week cleaned tested and balanced, with new o-rings and filters ready to install.

The electronic injecion is pretty robust on your car. ASSuming that no animals have nested in the airflow meter, you should be able to get the car running with minimal attention to this part.

You should be looking at the deteriorated vacuum hoses, replacing each tired cracked sectin one by one so you don't mis-route anything.

If you don't have a copy of the factory workshop manual already (referred to often here as the WSM), you are working with one eye covered and your ears plugged, good hand tied behind your back and ankles hobbled. We see print sets come around once in a while for ~$400. You can get a CD set with all the supplements from Roger@928srus RL username: ROG100 (sponsor here) for a fraction of that cost.

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And welcome to the group! Consider becoming a full Rennlist member for a very small cost. You'll be able to add a signature line and some header info to posts that includes your locationa and your car's specifics like years and model. It also lets you post pictures, and and adds some better access using the search functions.

Bruno DeSousa

thanks Rob for all that info!! i did some tests today and here is what i got.. the fuel regulators seem to be fine.. all 3 seem to hold vacuum. i also pulled the plugs to see what they looked like.. keep in mind that they are brand new..the 4 plugs on the driver side all were very black and wet with gas.. the passenger side plugs were also black but not as bad and also not very wet. not sure what that means.. im starting to think that the injectors might have to come out for a cleaning.. i cant think of anything else.. the vacuum lines all seem good.. this car even tho it was sitting the cloth braided vacuum lines all seem to be in great shape. i checked all the plug wires with a timing light while the car was running to make sure they were firing.. all wires are in the right cylinder...
also pulled the injector connectors one by one with the car running to see if there was a difference in idle.. the car idles extremely low once warmed up.. it barely stays alive.. i tried to adjust the distributor timing but didnt seem to help much.. i guess it could be a very weak injector spray?..but with the wet plugs im wondering if there is an ignition issue on the left side of the motor.. does that make sense?

while the car is running at idle.. i removed the vacuum line on the top of the vacuum advance on the distributor.. there was no change.. could that mean anything?

BTW.. my car is a US version no CIS

Bruno DeSousa

ill do a compression test on the motor tomorrow.. what is a good range for these engines?? also fuel pressure range? thanks in advance

Bruno DeSousa

oops

Bruno DeSousa

thanks guys btw my car is an 81.. soo blade style fuses?? what year idk..