1989 S4 A/T.....Traveling on the highway...lovely New England and pot holes everywhere and of course I hit one hard going about 55MPH. Blowout my right front. No problem. I get towed. I start her up to reverse it slowly into my garage and it won't idle for long at all. Stalls after about 5 seconds...Hold the pedal to the floor and it will stumble at about 200 RPM's...Central warning will light up saying my ABS is off. If I change the tire will it start...or what.?...Any help would be greatly appreciated...Strong running car with no problems at all before the blowout. Seemd very strange that a blowout would cause a startup problem. Thanks in advance.

 

Did the tyre stay intact, ot where there rubber fragment flying about ?

If debris was invlvoved, have a good look under the wing. See if any obviousldamage to the wheel liner and parts beneath it.

Sometimes a pot hole excursion is enough to kill an LH ECU. Let's hope yours is something more like a vac leak.

Regards

 

Nope ! the shock of hitting the pothole has knocked something loose. Think of it as if you drop kicked the computer on which you are reading this......... You might try disconnecting the mass air flow sensor under the intake to see if the car will then run in the "limp home mode " which is far far better than it will run now. Your 89 does store fault codes and might tell you what is wrong.

 

Also check the voltmeter reading: If the starter is strong, look elsewhere; however, a loosened cable may give you adequate voltage to turn over a warm engine, but not enough to satisfy the LH/EZK to run properly..

 

OK.....unhooked the MAF and got no "limp home" mode....just idles for about 3 seconds perfectly...then cuts out....I have pushed down/tightened every fuse and relay....and have unhooked both control modules/computers in the kick panel and hooked them both back...to no avail....Is it just a coincidence that a violenet/sudden jarring made the computer crap out?...Battery is fully charged, no loose connections and the tire did no damage...just crumbled and came apart ...Insight?.....thanks for the input in advance...

 

When it starts, is it running on all cylinders - or on half? Check the red/green diodes on the EZK relay if the latter.
Perhaps disconnecting the battery to promote a LH reset could help (as you may surmise, that's a shot in the dark).
Any indication at the tailpipe? A low idle is normally ummetered air (leak) - but a chance it could be excessively rich - and puffing black smoke rings.

 

I have known of several LH ECUs that have failed after a pothole excursion, or even just when driving along.

If it will start at all, then there is a chance that the problem is something other than LH failure, although they can fail partially e.g. with WOT enabled all the time.

Start it up, and try and keep it running until it warms up if you can. Then do as Garth suggests, and try to determine whether it is runing on all cylinders, running rich or weak, and so on.

It is worth trying to find out why the ABS light is on. This could be related to the engine problem.

 

I believe the car is running on all eight cylinders since the idle sounds perfectly normal for about three seconds. No smoke from the RMB. I just cant get the car to run for any length of time. Does the led on the EZK relay come on with the key in the ignition or does it just light up when it runs for any length of time? Mine does nothing ...The relay clicks when the key is turned but no light...Thanks so much for the help.

 

You might try checking the fuel pressure. Big vibrations from "off roading" has killed more than one pump. The pump in the tank could be broken, blocking off the flow to the main pump. The main pump might have died and the pump in the tank is trying to supply fuel.

greg brown

 

https://rennlist.com/forums/showthre...ight=ezk+relay
https://rennlist.com/forums/showthre...ight=ezk+relay
https://rennlist.com/forums/showthre...ight=ezk+relay
https://rennlist.com/forums/928-forum/191459-4-cyl-mode.html

Excuse the long list above, but some useful reading contained within: Extracted them from the archives while thinking out loud ....
Assume you've done a battery disconnect to reset the brains by now, and have a fully charged battery at 12.3v or higher.
If firing on all eight, the EZK relay is functional - and no lights is good. Does it idle at 700 rpm, and then drop to ~200? - or never get up to 700? Actually, a cold start should see up to 1100rpm.
As it stalls, by the description, it would appear that the fuel supply is cut off: this could be the fuel pump relay, maybe the fp itself, or the controlling signal to the pump; therefore, it may be worthwhile to a) swap the fuel pump relay (horn relay), and/or jumper pin 30-87 of the pump. The 928 Specialists site have excellent fuse/relay charts if needed - good for the glovebox, courtesy of DR.
By jumpering the relay, you should be able to confirm fuel flow/pressure: do not leave it jumpered for long with out the engine fired ( test only).

 

Disconnected the battery...to reset everything and now it will just turn over and not run at all....I think I may be heading to an area Porsche dealer since I do not think I have the ability to check the fuel pressure..... I appreciate everyones input.

 

Dealerships likely know less about the 928 then you do!
Post where you are, and see if someone nearby can recommend a good INDEPENDENT mechanic that knows sharks!

 

I am in Swansea, MA......Which is 12 miles east of Providence, RI and about 45 miles south of Boston, MA...I have emailed two Rennlist members who are from MA and have not had a reply back....Only sent the messages about 20 minutes ago....4PM EST

 

Board is a little slow on the weekend. Hold tight and someone will come to your rescue. Please let us know what you find out is the culprit.

 

Holding Tight...