cjfisher

Im pulling my hair out with a customers 928. Car came in would barley run. I don't have a Hammer so I started testing across the wiring harness and only found that the 02 was out of range and the car could not achieve WOT. Ran the car on the lift and cats glowing red. They were obstructed so I fabricated test pipes and swapped the 02. Still wouldn't idle so I unplugged the MAF and no change. Ran smoke test and found multiple intake leaks. Pulled intake and it was a mess. Bad gaskets and vacuum lines. Knock sensors completely deteriorated. Replaced both sensors, valves and guides in great shape, compression great and only 1-2 lbs. difference between cylinders. Complete gasket set. Car starts and runs smooth, great idle. Ignition timing at idle at the 20 to right of the 0 and under acceleration goes to 4/5 mark. Fuel pressure ok. The car is gutless! its an automatic and even shifting manually 0-60 time of 18-20 sec and will barley run 4000 rpm. I don't have an oscilloscope or hammer so I'm at a point where I can only replace parts and hope, which goes against my ethics. Is there anyone in the NOVA/DC/Metro area that can come over with a hammer and or oscilloscope and run some checks on the system? Check the HALL? Offer any guidance? I guess I could pull the timing covers and make sure it didn't jump time but the starting, idle and vacuum is all stable but then again I am only going on my experience with single cam v8s.

703-898-7511

DKWalser

It would be helpful if you'd tell us the model year of the car.

SteveG

It would help to know the year of this car re CE panel and ignition protection circuit. You say the cats glow red and later that it is gutless. Don't know what to make of that contradiction, except on re-read that "gutless" doesn't refer to cats??

Not sure what this means.

You don't have to pull the TB covers to check the belt, at least not for ballpark. There is a notch in the cam gear for TDC that is visible from the vent hole at the top of each cover. I doubt this pertinent as it wouldn't idle well.

Others here will know more.

fraggle

If the cats are glowing it is likely an ignition issue. One of the coils or a coil wire has failed.

Where in NoVa are you?

SeanR

Would be my guess if the cats are glowing. It's dumping un-burnt fuel. I'd check to see if the if you have spark at all 8 cylinders, if not work back wards and find out why. Two coils, two coil wires, two ignition amplifiers. If the car is a later S4 it could be as simple as that crappy ignition monitor relay.

Randy V

Welcome to the forum.

It is always recommended to use a thread title that describes the topic to allow it to come up in archive searches of thread titles.

Also, breaking your post into paragraphs makes it easier to read.

As mentioned, if the cats are that hot it indicates raw fuel is dumping into the exhaust, typically caused by poor ignition, i.e. a coil failure. This condition has resulted in more than one catastrophic car fire.

davek9

Never did see the year of the car posted or did I miss that?
I just assisted a local who's 56k mile early '87 burnt up due to a CAT fire, lots to rebuild now, don't drive this car until this is resolved!!!

cjfisher

sorry guys. its a 1987 s4.

Mike Frye

knock sensors implies S4. otherwise no idea

ha ha. tie goes to the OP.

cjfisher

Getting to all of your questions. 1987 928s naturally aspirated, automatic 78,000 miles, condition is nicer than mileage would indicate.

My shop is in Aldie, Virginia. (south of Leesburg west of Chantilly)

I never suspected the ignition because it idles well but does seem to break down at 3000 rpm. The plugs looked consistent (visually) when I ran the compression test.

Sorry for the format of the post. I will take the advice. Thank you.

Cats are off the car now and rattle like crazy. Lots of dislodged catalyst rattling.

I do not claim to be a Porsche mechanic but every car has the same basic systems. I appreciate all of your input and tips.

fraggle

Oh oh, better suit up!! /flame on/

davek9

Get a simple timing light and confirm u have spark to all the plugs, if you find that 4 don't work two in each side, you have a dead "ignition bank", look at het distributor caps and start from there.

Next would be pull all the plugs and see if any are fouled, could be a stuck or leaking injector.

Edit:
An '87 has no way of knowing if an Ignition Bank has failed, the Fuel Injection on all of them is Batch Fire, (all injectors fire at same time), they are all under pressure and just switched open via ground via the LH Computer. Newer models have Temp sensors that can turn off 4 of the injectors, that's why the year is important.

Dave

michaelathome

CJ,

I am in SR, right next door. I would check the coils as well. If you look at the routing of the spark plug wires they cross in the front of the engine 1,3,5,7 and 2,4,6,8. In that way if one coil failed you would still drive. All that unburned fuel is heading into the cats and igniting there as the exhaust exits the block.

We had another NoVa owner ignite his car in this same manner.

Michael

dr bob

Sorry I/m a little late to the party...

Most Common failure for your symptoms seems to be one failed or disconnected coil wire, followed by the coil itself and then the ignition module (on the front apron driver's side, under a black plastic cover). That's after the traditional cap & rotor inspection of course.

The engine will idle OK on four cylinders as you discovered. By this age and regardless of mileage, virtually all driven S4's are due for new hoses and sensors under the intake. There are only a few gotcha's around deteriorated electrical connectors at the MAF and throttle, and the connections to that solenoid at the front of the driver's side belt cover is directionally-sensitive on the vacuum side.

Ignition wire sets are best replaced with the Beru pieces, as they perfectly match the originals and include all the holders and are numbered for the correct cylinders. Coil wires are different between early and late S4's, noted by the ends going to the coils. There is no resistor in the coil wires so they should Ohm at near zero. Plug wires have resistors built into the plug connector but solid wires, FYI.

The car owner is fortunate to have brought the car for service immediately on the symptoms. Most folks seem to try to drive through or may not even notice the car running on four cylinders. The raw fuel passing through will quicklt cause the cats to overheat, igniting undercoating and interior stuff and quickly turning the car into a crispy critter.

Mrmerlin

CJ the most probable issue will be the coil wires failing , not the coils its usually the left side.

NOTE this can be confirmed by running the engine in the dark ,
remove the intake tubes and watch for fireflies along the wires.

NOTE if the cats are glowing you have about 3 mins from cold start for them to be glowing.
then one of the ignition systems has failed, see the coil wire first,

NOTE what you will be looking for is corroded coil wire ends ,and to verify that the coil wires dont touch any part of their run ,
it might be best to run the car in the dark before you mess with the coil wires so to confirm this diagnosis.

Note if the coil wire is bad, new coil wires can be purchased separately .

NOTE if you find one set of 4 plugs not firing then swap the plugs along the front fascia panel for the ignition modules,
these are under a black cover about 8 inches to driver side of the hood latch.

The Hall sensor is also a performance blocker if its not working and if the knock sensors were bad,
then odds are the hall is also bad.

The hall sensor is behind the right hand cam tower and the connector will usually be crumbled .

NOTE the crank position sensor should also be replaced due to the same crumbling connector,
as well as the fuel lines