Daymon66

thanks Ryan, you're frst in line.
it could be about a dozen things. none of which i have parts for and no way of trouble shooting.
i'm going to take off work tomorrow and see what i can come up with. i can't stand broke **** and even worse i can't stand not knowing what it is.

thanks all.

928autobahndreamer

If it is in 4 cylinder mode don't run it as you are dumping raw fuel into the cats and if run too long can cause a cat fire. As far as the cause, be patient, there are some great 928 minds here. I wish I could guide you, but I am a bit of a 928 newbie myself, mechanically speaking.

Mike Frye

I have read about this too. It's weird because some people say it goes into this 'limp home mode' to avoid a fire, while others say it can cause a cat fire by dumping raw fuel.

You can confirm how many cylinders you're actually running on by *carefully* removing one plug wire at a time while it's running. If it doesn't change the sound when you pull it, then it wasn't firing anyway.

I think the 'limp' mode is only one bank (like just the left side or just the right side). Is it possible you just have a bad or loose coil or distributor wire? This would account for lots of cylinders going dead at once, and could have happened all at once.

I'd check for loose wires around both coils and both distributors, then start it and see if I can isolate which ones are firing and which aren't. Then report back and/or search to see what you can find in the archives here.

dr bob

"Limp Mode" and 4-cylinder mode on '89+ cars are two different things. "Limp Mode" is a mapped mixture that lets you get off the freeway when your LH detcts a MAF failure. 4-cylinder mode is used in '89+ cars to avoid catalyst fires when one ignition system drops out for some reason.

Let's go with 4-cylinder mode for a bit. Hidden by the cover on the right side of the passenger's footwell you'll find the two engine brains. EZK for ignition is closest to the center of the car of the two, while the LHA for fuel is closer to the right side panel. The cover snaps off and un-tucks from the junk tray, then folds toward the middle of the car to reveal the modules. Above the modules on the support bracket is a relay called something like the EZK protection relay in the WSM. The EZK protection relay looks at the temps of two exhaust ports, and if one is significantly colder than the other (typical to one failed ignition), it will turn off the fuel injectors to the set of cylinders that's cold. Two left and two right cylinders. You can look at that relay and see if it's working. There's a red and a green LED that light up when one of the channels has dropped out to protect the catalyst. Pull the cover, then get a volunteer to sit and watch the relay while you drive it a bit. If it lights one of the LED's, look for ignition problems for one of the distributors. Might be a coil wire loose to a distributor cap (there are two...), one of teh caps or one of the rotors inside. On very rare occasions the little amplifier module on the front apron fails, and perhaps slightly more often a coil will fail. Still pretty rare.


Here's a thought though. You sat there with the key on for a bit before actually starting the engine. The protection circuit isn't that smart, and thinks after a while the engine should be running and the exhaust should be hot. Then you actually start the engine, and the protection relay drops the fuel to 4 cylinders, so that the exhaust really is colder. That relay is doing exactly what it was designed to do. You fooled it with the key on but no start action. So--- I recommend that you let the engine/exhaust cool off for an hour or two, then try to start the car normally. My nickel to your dollar says the engine will start and run fine when you do that. PM me for the adress to ship the dollar, or where to send postage so you can get your nickel.

Daymon66

thank you dr bob.
car never got warmed up. i will check all those things mentioned and see what happens. i was kinda thinking i may have trick ***'d something by not starting it right away after turning the key all the way.

i found a post from a PO 928andRC51 and he had the LH replaced a while back. i'll go thru and check all wires and connections. i did wash it (car not motor)friday and then again saturday. we also had some rain and it did have to sit in the rain for a little while.
so damn odd. it was running strong and perfect.

hoping i'll wake up in the morning and it'll be running fine.

worf928

Just to make sure we're all on the same page....
... The protection relay LEDs will only light up IF the motor is running. AND, IIRC they don't blink. They are either on or off. Off good. On bad.

If it feels like its running on only four cylinders then it probably is. Make sure both coil wires are secure at both ends. Check that the plugs on the two amplifiers under the black plastic cover at the very front of the engine compartment are snug. If those simple things don't fix it then you'll need to dig deeper.

EDIT - And follow DrBob's directions on how to check the relay once the motors turning.

Mike Frye

Daymon,

Go with what Dr. Bob says instead of mine. His information about the 'limp mode' and 4 cyl mode is much more detailed (and correct, I'm sure) I was just guessing at that part. I just wanted to suggest checking each of the plug wires to see what's firing. If it was running really strong and now it's choking I'm sure it's something minor and you'll be on your way in no time. Loose wire, major air leak from a loose intake boot, something like that.

worf928

One more thing - IIRC - "save power" is the same as the idiot light for the alternator. The car doesn't think the alternator is charging...

Daymon66

hey dave, car was started when i was looking for LED's

thanks to all for the "path".. i'll dive in tomorrow and see what i can screw up..

dr bob

I can hardly wait. My wife says I need the dollar....

worf928

The ignition monitoring circuit reacts to differential temperatures (voltages) from the two EGT sensors. So, it wouldn't be fooled simply by leaving the key on. Also, there's an 18 second delay after motor start before the relay will 'do its stuff'. So after starting the car you have to wait to check the LEDs.

RED LED indicates ignition problem on cylinders 1, 4, 6, 7 (right side (p-side on LHD.))
GREEN indicates 2,3,5,8 (left side.)

Ispeed

Unless Sias rebuilt the LH, it is original. I rebuilt the LH on my 87 when it died in '06. Another thing is that some new plug wire sets do not include coil wires, and original bad coil wires could cause 4 cyl running intermittently. That was happening to my 87 and giving me similar symptoms.
My home computer is down and I'm on the crackberry...

AO

If it does it again, I'd pull the spark plugs and compare. That's what led me to find my head issue. I'm thinking good thoughts for you.

Daymon66

hey guys, started it this morning and same thing. idles rough no power.

i failed to mention previosuly that on saturday after parking it i got out locked the doors and released the hood so i could look at things. shut the door and when i went and open the hood the horn started honking. i placed the key in the door and opened it up and horn stopped. Sias told me that this car did not have a factory alarm so i guess that was just a general security feature. i do know that my door lock pins have red LED's in them and they flash when the car is locked.

was thinking that that may have caused something????

i am at the office for a little while today and plan on getting into it when i get home.

thanks again for all the advice and i'll update.

AO

Sias was wrong... your car does have a factory alarm - as you discovered. Unfortunately this should have no relationship to your idling problem.

Answer this for me...

When you start the car, after 20 seconds or so, does it loose even more power?

I ask because , the way the ignition monitoring relay works is if it detects one bank (1-4-6-7 vs. 2-3-5-8) is not running properly, it will shut down the entire bank. This just happened to me recently.

If there is no change, then I would suspect a coil wire or the coil itself is having issues. (Had this happen to me too a couple years back.)

Per my earlier suggestion, you might also try pulling the plug and post a picture.