944 idles fine dies when you drive

[dangerous]

Hey all

I'm having a bit of trouble getting my 944 back on the road and was wondering if anyone could give me some advice?

THE STORY:
looking for some ideas if anyone can help. My 85.5 N/A hasn't been on the road since last July. I've been working on several areas of the car since then. Pulled the head and had a valve job done, cleaned piston heads, replaced front seals, belts and pulleys, new plugs, cap/rotor, air filter, fuel filter, oil filter, head gasket set, cleaned the throttle body. Put it back together and it ran kinda rough so I messed with the throttle mixture process (jumper wire between B & C on the diagnostic plug). Took the car to P-Tech to have him check my belt tensioning work. He said my belt was off two teeth and my water pump and radiator was leaking. I drove it home and along the way the car kept dying, initially it would start back up but soon would stall again until eventually it would not restart. I noticed that the voltage was lower than normal when it was running (dash guage)....around 12V instead of 13-13.5V that I was a used to seeing. Let it sit for a few minutes and it would start and run for a couple minutes before dying again. Eventually limped back home after a few restarts.

Went back under the hood to replace the water pump, repaired the radiator at a radiator shop. I was suspicious about the alternator so I pulled it and took it to Autozone so they could test it. The kid there had trouble testing it (didn't look like he really knew what he was doing) but eventually got it to run a test and said it was okay. Put it all back together (marked the belt so I could put it back in the right place) but wouldn't start due to weak battery. Had Batt tested and they said it ws bad so I bought a new one. Car started right up. Idled rough but managed to bleed the air from the cooling system when it warmed up. Reconnected the jumper wire (to B & C) and adjusted the idle bypass screw and car sounded much better. Idled with occassional slight miss but seemed to run pretty well. Lowered the car and went for a test drive. pulled out of the parking lot turned a corner and it died again. Voltage was aroud 12 V dropping to around 10V when I cranked it to restart. It started and ran for about 4 seconds then backfired out the tail twice before dying again. Would not restart, although would fire a little while cranking, wouldn't run though. Pushed back home and went out for a sandwich.

I'm still suspicious of the alternator due to the low voltage. It would be normal when first started but would slowly drop. I'm wondering if I need get it to die again then check the basics, look for spark, etc.

The Alt measured 13.7V at idle then held 13.6V idling with the fans on (digital tester on Batt). The guage seemed just a tad lower than I recall it being though.


Sending out an S.O.S.....

Thanks
Eddie

[dangerous]

What about any ideas of what could cause the car to die after less than a minute of driving but didn't seem to affect if while idling?

Could the alternator be be in a condition to idle the car fine butthe added load on the engine from driving push it over the brink and cause a failure?

I'm considering wiring up the voltage meter to the BATT and running it into the wondow so I can monitor changes when I try to drive it.

Anythoughts or aideas welcome and truely apprecited! Thanks.

[ae1969]

I think you may have a couple issues still to iron out.....

1st Thing. Make sure all your grounds are clean and tight. The wiring on these cars are BRUTAL. Connectors may look good only to be completely corroded in the inside. Look at the grounds on the bellhousing. The grounds by the front drivers headlight. The grounds on the battery should be clean enough for me to eat off. Attaching the digital voltmeter while you drive is actually a good idea. It will at least give you an accurate reading.

You may alsoe have an intake/vacuum leak (popping) still but lets make sure the charging system is working properly first.

P.S and when I say clean I mean a wire brush, sand paper anything to make the connections metal-metal.

Report back. THe battery voltage of 13.7 is ok so I think you only have an intermittent wiring problem.

[McClintock16]

definitely check for vacuum leaks too. sounds to me like you have a couple problems to sort out. Im sort of confused as to what exactly is happening though... does it drive fine for a little bit then die? or does it die as soon as you put load on the motor?

[dangerous]

Alex - Thanks for the recomendations...I will check these things today. I was seaching through old posts 'til 3 am, making notes about similar probs others have had...I was surprised how often the "bad ground" and elec connection issue came up. I never realized it was such a prob. I'm on it and will keep you updated.

McClintock16- There are actually three occasions to speak of (the only three times the car has been driven in last 10 months.)

1st time: When I finished the head RR/valve job, and front seals, timing belt, etc, I started the car and it ran kinda rough. I had cleaned the throttle body and was advised that I may need to adjust the idle bypass. Didn't help much. I needed to have my Tbelt tension checked since it was the first time I RR the belt and I tensioned it with the Kriket. So...local Pmech is not far and I could take back streets, so I drove it to him. It ran kinda rough but didn't stall until after 7-10 min of driving..... stalled a couple of times but started back up each time.

2nd Time: After the Pmech determined that my Tbelt was off by two teeth and I had coolant leaking from my H2O pump (prob killed the bearing when I retensioned belt) & Radiator, I was willing to drive it home since the leaks were slow, and I didn't live far. Along the way home it ran okay for the first 5-7 min then stated stalling again. The first few times it stalled it would start right back up. A few min later it wouldn't restart after stalling unless I let it sit for a few min. I had noticed the voltage was lower than norm (on dash) so I was suspecting Batt/Charge system. After some patience, I did manage to get it home.

3rd Time: Went back in and RR H20 pump & radiator, and RR alt which load tested OK. Car would not start due to dead Batt. RR batt and car started up but ran rough. Bled cooling system and readjusted idle bypass and car was running MUCH better (I messed with idle before but prob was tbelt off 2 teeth). I idled and reved engine for 15-20 min checking voltage w/ meter at batt, cheking fans, temp, etc. No probs. Seemed to be running pretty good so I took it for a test drive. Made a Right turn out the parking lot and another Right on the first backstreet and the car died. It restarted and ran for about 7 seconds before stalling again with 2 rapid succession loud pops from tailpipe (I previously described as backfires but they actually sounded more like loud pops). Wouldn't restart so I pushed it home.

Both You and Alex mentioned vacuum leaks and that too makes me think. I had a bad hose under my intake man. It was a little S-shaped thing with one end slightly larger than the other. I think it connected the Manifold to an idle stabilizer thingy if I'm not mistaken. Anyway, I couldn't find a replacement (even dealer said NLA) so I made one out of hose I cut. It seemed to fit without kinking but there was a slight bend to make it fit. I'm kinda suspicious though.......

[earlr85944]

just something to consider although it may be multiple issues,:not running since last july- possible bad fuel\clogged\sticking\ injectors or fuel delivery problem.
when you have a no start condition or the rough running: check for spark at each sparkplug wire and for steady fuel from each injector.

[dangerous]

earlr85944
Thanks....I will follow your recommendations too. I was kinda worried about the extended down time and the impact it may have on the fuel injectors and FI seals. I didn't think about the the fuel condition at all....but I did put in a new fuel filter. I know I've read posts on here somewhere about the proceedure for cheking the fuel injectors (elec and fuel flow) so I'll run a search on the old posts.

[ae1969]

If you have a vacuum guage connected to one of the vacuum lines.

Uhmmmm I hate that idle stabilizer valve........... but since we have to live with it.

Try this and tell us if it runs better.

There is a diagnostic port...........Place a wire between B and C.
Take a look at this diagram. Start the car up and see if it idles better. http://www.clarks-garage.com/shop-manual/fuel-08.htm

[earlr85944]

i do it the untechnical way: i unplug the coil wire , pull the fuel rail, prop it up, put a disposable towel under it and have an assistant crank it while i watch the injectors fire. Since you name is dangerous you dont even have to put out your cigarette. Just kidding, the injectors will spray straight down into the towel and slow enough for you to see the amount they are discharging.

[dangerous]

update:

I checked and cleaned the pos and neg terminals on the batt, cleaned the ground where batt connects to the firewall, and the ground conction near the headlight. I haven't found the ground between the bell housing and firewall yet. Tomorrow I will clean the terminals on the alt and lift the car and clean the terminals at the starter.

Can anyone describe where/how to get to the ground connection at the bell housing/firewall? From under the car or through the top....etc

Also, I found a slightly damaged wire leading to my O2 sensor on the lower exhaust. It's not severed but the white insulation is worn away exposing the steel wire. NOTE: I'm not running a cat/conv these days. Not sure if this could affect any of my problems though.....wouldn't a bad O2 sensor wire just affect milage?

Oh yeah, I also found my vacuum line for the heater control valve was disconnected. Would that cause a leak throughout the system?

Alex, where would be a good place to connect a vacuum guage and what kind of readings should I be looking for?

I had already readjusted the idle bypass but may have to play with it a little more. I would adjust it to around 900rpm and when I removed the jumper the idle would rise to around 950rpm. The jump seemed a bit much but it's hard to really tell until I get a tech/dwell on the engine, I was only using the dash tach when I did this.

Tomorrow I will also pull the fuel rail and check for flow using earlr85944's method....I like to live dangerously.....

More updates tomorrow

Thanks for your guidance....I appreciate it greatly.

Eddie

[IceShark]

Eddie,

You get to the bellhousing ground from the top as I don't believe you could ever get your hand to it from the bottom. You are going to have to move some wires and probably the heater hose to get your hand down to the stud.

Once you clean up the connections you can't totally cross neg and pos cables off the list. As Alex noted you can have corrosion inside the terminal. Porsche used bare copper (not tinned) terminals that are mechanically crimped to the wire core. They are not soldered or sealed. So, corrosion walks up the interface between the terminal barrel and the wire core. Not much you can do about the problem other than chop off the old terminal and replace or just replace the cables altogether.

[scheistermeiste]

how old is the cat? i had a similar problem on a different type of car. what happened was that the car would idle fine but when i tried to drive it it wouldnt rev past 2k and when i let off the gas it would die. i thought it was a blown motor (rotary) but when it was sitting in my drive way i got pissed at it and just held the gas down all the way reving the crap out of it (well up to 2k where it sounded like it was bouncing off a rev limiter) after about 5 min it back fired louder than usual so i let it die. when i walked to the back of the car there was a VERY large chunk of my cat that had been blown out of the tail pipe.

what was going on was that it would be fine idling but once it heated up the guts of the cat started to melt blocking off the exit. once i let the car sit for a little while all the innerds would settle down and get hard again.

just an idea

[dangerous]

Originally posted by IceShark
Eddie,

As Alex noted you can have corrosion inside the terminal. Porsche used bare copper (not tinned) terminals that are mechanically crimped to the wire core. They are not soldered or sealed. So, corrosion walks up the interface between the terminal barrel and the wire core. Not much you can do about the problem other than chop off the old terminal and replace or just replace the cables altogether.

Iceshark
here's what my terminals looked like before I cleaned them. They copper between the wire insulation and the crimp is certainly corroded but I could imagine they could be much worse. What do you guys think, are they bad enough that you'd replace 'em? I'm kinda leaning toward it.

[dangerous]

Scheistermeiste

I melted my cat and removed it about 7 years ago so it's just flowing straight. The kitty still purrs though (well apart from the present dilemma I guess).

Those fudge pops ain't gonna get me.....

[IceShark]

Those are actually the supplemental positives and those are tinned. I'd hate to see what the main cables look like as those are bare copper.

It is unlikely you could ever get solder to run down those at this point unless you acid bathed it which isn't good for the wire. See if you have enough slack to clip off the terminals, clean up the copper wire, re-crimp new terminals, solder and then seal them.

Then see what happens.

[dangerous]

I think there's enough slack to do it.....I'll go look for some new terminals then.

Thanks!

[parispat]

Hi,

Greetings from paris, FR.

I have an '88 944S with EXACTLY the same symptoms. The car would start right up, then after 5 minutes, it would die off as if being chocked to death.

Wait 30 minutes and it started again.

Now it won't start at all.

Fuel is arriving, spark verified as ok in an extra spark plugged into spark plug wire.

HOWEVER . . . using a 12v led (very low drain, no damage to system) plugged into fuel injector plug head, I found that there was no electricity arriving to the feul injectors.

As the symptom was related to heat (reaching running temp) could there be an electronic module gone bad?

TIA

pARISpAT

[parispat]

2nd posting:

I'm told that the 944S engine (2.5L, 16 valve) is the same as that used in a VW light truck.

Anyone know what VWs used this engine - in hopes of cross referencing problems and parts!

TIA

p@

[parispat]

3rd posting: next day

From Clarks-Garage.com

...Symptoms of a failing DME relay may appear in several ways. Early on, the car may not start or be difficult to start when the engine has been shut down and restart is attempted while the engine is still warm (actually while the DME relay is still warm). When this happens, the car will normally restart when it is allowed to sit and cool for a period of time (usually from 30 minutes up to 2 hours). Another possible failure mode is for the car to suddenly die while driving down the road. Again, the car will often restart after it is allowed to cool.
If your car will not start and you suspect the DME relay may be bad, try tapping on the DME relay and then attempt to restart the car. You might also have an assistant tap on the relay while you attempt to start the car. This will often temporarily fix the DME relay to get the car started.
If you experience a DME relay failure and you can not immediately get a new relay, you can get the car home by removing the relay and jumpering the relay terminals on the relay / fuse panel to supply power to the DME and fuel pump. DO NOT leave the jumpers installed when the car is not running. This will cause the DME computer to be continuously energized and the fuel pump to run continuously which will drain the battery. Jumper fabrication and installation will be covered later in this procedure.

1. If you suspect the DME relay is bad and you need to move the car, you may install do so by installing an "emergency" jumper across terminals 30, 87, and 87b on the relay / fuse panel. Some folks will tell you to jumper terminals 86, 87, and 87b instead. This allows you to only run the fuel pump, DME, and injectors when the ignition switch is turned on. Seems like a great idea on the surface. However, realize that the wire supplying power from the ignition switch to terminal 86 on the DME relay is a 1.0 mm wire and is only intended to carry enough current to pickup the primary coil on the relay. The wire connected to terminal 30 is a 4.0 mm wire which is designed to carry full current demanded by the fuel pump, DME, and fuel injectors. I strongly recommend using terminal 30 instead of terminal 86 to supply power via the jumper...

Refer to www.clarks-garage.com for complete write up.

[dangerous]

Tremendous gratitude to all who keep this forum active and generously share their knowledge and experience!

The progress has been delayed by a few setbacks but here's the latest!

All grounds located and cleaned. A few unrelated problems discovered and corrected....delayed by waiting for parts delivery.

My 944 started right up and idled a little eratic for a couple of minutes then smoothed out well. The car idled without any problem for more than 20 minutes while adjustments where made and cooling system was bled and checked for leaks. I shut it off and connected leads from the batt into the cockpit where my voltmeter was connected. The voltage readings were recorded by my co-pilot who monitored the meter constantly and recorded data on a clipboard.

Incident: Battery voltage readings:

Engine off 12.75 V
Starter activated 11.63 V
Engine running at idle 13.54 V
Engine running at idle 13.57 V
Headllights activated 13.48 V
Headllights activated 13.51 V
Driving 13.54 V
Driving 13.57 V
Driving 13.67 V
engine sputters 13.69 V
engine stalls 11.82 V (voltage drops after engine stall)
coasting with engine off 12.56 V
sitting engine off 12.40 V (following failed restart attempt)
sitting engine off 12.48 V
sitting engine off 12.57 V
starter activated 10.90 V (will not restart)
sitting engine off 12.50 V
pushed car home 12.54 V

The symptoms seem to be unaffected by ground connection improvements/cleaning. The car idled without any noticable problems for more that 20 minutes. On test drive, car drove fine for a several minutes at parking lot speed (1st gear). Car drove fine at low speed (2nd gear). Engine felt strong during gentle acceleration (up to 3rd gear) then sputtered briefly but didn't stall immediately. Car continued to run for another couple of minutes, then there was a sputter and and engine died suddenly. Engine didn't restart after several attempts and after waiting for about 5 minutes.

Tomorrow I will check voltage at fuel injectors and check fuel delivery at fuel injectors as previously recommended.

Also, this DME relay problem posted by Parispat (from clark's garage) sounds suspiciously like my symptoms. I am assuming that if I find no volts at fuel injectors or no fuel flow, this could be the cause. Can anyone who may have knowledge or experienced DME relay or DME problems rule offer any insight?

I will try to check the DME relay tomorrow.

Could the DME itself be the problem? Would it still run intially if there was a DME problem?

Thanks in advance!