17prospective buyer

Throttle switch maybe?

jpitman2

What idle revs do you see ? Check the specs, and set it properly - mine is 750+/- 50. Only tries to stall when you back off accelerator? Some models have a diaphragm thing connected to the throttle body to do with excess vacuum, so this might be involved. Also check that you have no air leaks in the intake anywhere - spray something like wd40 , kero etc (ie not dangerously inflammable, but flammable) over any joints , and listen for a change in idle, or visible/audible sucking in. No brake booster problems?
jp 83 Euro S AT 55k

outbackgeorgia

No idle adjustment on the S4, set by the LH computer. Possibly a vacuum leak (most likely) or the idle air control valve under the plenum. I would look for a vacuum leak first.
Dave

CDJQ

Thanks for all the suggestions. Tomorrow I will do a thorough search for a vacuum leak and see where that leads me..... Hopefully it is that simple!
Brett

CDJQ

Okay, I am back....
So I have looked into some of the suggestions and there were some eye opening revelations. Using the old "carb cleaner" trick I found the Y pipe from the oil filler neck was disconnected under the manifold. I am guessing that this happened during the Timing Belt service & Crank Position sensor work I had done in 2009 (The car was in storage since then that is why I never noticed it - plus when it left that shop it was trailered down to Florida). Prior to hooking this up I would start the car and the idle would be very rough and undriviable - so that was a great find... thank you! Anyway once I hooked it up the car ran sweet, probably the best I have seen in years..... for about 15 minutes - then it choked and died. Now it will start but stall out shortly thereafter. I pulled the MAF connector off and it will start and idle okay for a few minutes but then die also.
The MAF was rebuilt in 2011 and hasn't been used since then.
I checked the voltage on the Ignition Relay, Fuel pump relay and the LH Jetronic relay and they are all good. I also jumped each one of those and the problem still remains.
Today I also did some cleaning up on wire connections that looked iffy (temp II, Knock sensor).
So basically the car was running better before I hooked up the vacuum hose.... Strange right?
Some history that may help.... I had this car in the shop back in 2009 for this same problem and it left the shop three times and died as I pulled out of the parking lot. Because I was moving I ended up leaving the car there for a while for the Timing Belt service (and supposedly to fix that other problem). Since then it has sat mostly in storage. While it was in for the Timing Belt service they also replaced the MAF Crank Position Sensor and the MAF connector(I am guessing this is when that hose wound up getting knocked off).
So any thoughts of where I should look next? The Fuel injection brain was done in 2001 so that has been quite a while.
Once again thank you for all the excellent help here!
Brett

jpitman2

Cold starting OK but dying as it warms is commonly connected to a failed temp sensor - does the exhaust smell rich and sooty as it warms? If so the temp sensor is saying its still cold, keep it rich, so it chokes in the end.
jp 83 Euro S AT 55k

CDJQ

Hi Jpitman2,
Thanks for the info. Actually I don't know if the exhaust smells rich because the car does not want to start. So today I started to dig in and noticed that the CPS wire looks pretty bad near the connector - so I am going to try to fix it up as best I can just so that I can test to see if this is the culprit. I assume that if the CPS wire is shorting out that the car won't run or will run terribly.
Now that I am flashing back in my memory to when this all originally occured (circa 2009) I think that when it was choking we shook the air box and it jumped back to life. At that time the MAF connector looked like junk so we replaced it but that only fixed the problem temporarily. Maybe all along it was the CPS wire?
Thanks for all the help, it is greatly appreciated.
Brett

Mrmerlin

If you have not already done so I would check the crank end play, this requires lower bell housing removal.

NOTE a quick check is to remove the dipstick ,
get a single side lamp cord about 25 inches long,
and put it down the tube, pull it out then drip the oil onto a black piece of cardboard,

look at the oil in the sun,
if you see lots of metallic flakes then thrust bearing failure is indicated.

Otherwise with the S4 there are lots of connectors that need to be replaced ,
and on a car thats been sitting,
its pretty common to replace the CPS, Hall, and both Knock sensors,
this is usually done at the intake refresh .

If the fuel tank has not bee drained and inspected for fresh fuel,
then that should also be done so you dont damage the new pump

17prospective buyer

Where in this thread was possibility of TBF mentioned?

CDJQ

Thanks for the post Mr Merlin. I have not checked for the TBF issue yet but it is on my short list before the car comes down off the jacks. The CPS was just replaced as well as the one knock sensor, MAF, and the Timing belt was just done recently. During the fuel pump replacement I did empty the tank and put some fresh fuel in it.
My intention is to just diagnose this no start / awful run problem first and then once I am confident it is running I will refresh the top end (although a thorough refresh was done just prior to my buying it in 2001 because the previous owner busted the timing belt and smeared the heads).
My hope is to get it running as well as it had been between 01-09 so that I don't create more problems before the refresh.
Okay I am off to the garage - wish me luck!
Brett

WallyP

I suggest checking the Temp II sensors - free and easy, if you have a multimeter. (And if you don't, you need to buy one - they aren't expensive. Harbor Freight will often give you a free one!)

The Temp II sensor sends the coolant temp to both the ECUs. It is located on the coolant crossover, front top of the engine. There are two identical temperature sensors, one for the ignition and one for the injection. Check the resistance of each pin to ground - not pin to pin.

The resistance at specified engine temps should be:
32 deg F - 4.4 to 6.8 kOhms
60 - 85 deg F - 1.4 to 3.6 kOhms
104 deg F - 0.9 to 1.3 kOhms
140 deg F - 480 to 720 Ohms
176 deg F - 250 to 390 Ohms

If the Temp II sensor (or its wiring) is faulty, it can cause the fuel/air mixture to be too rich when the engine warm, and can prevent the control system from ever going into "closed loop" mode.

CDJQ

Hi Wally,
Thank you for that. Yes I have a multimeter & I will check these this afternoon. Glad you told me pin to ground.... I would have thought pin to pin!
Brett

CDJQ

Okay - checked that Temp II sensor and it read 3.4 k on each pin so that is all good.
Onto further review of the CPS boot

WallyP

You really need to know what the resistance is with the engine hot...