Loss of Power then Rough Idle...then Stall....
02-28-2003, 07:22 AM
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Loss of Power then Rough Idle...then Stall....
After months of trouble free driving my 87 928s4
started to loose power on my way home. I managed to park in a side street where the revs fluctuated wildly almost stalling while the car was in 'Park'.Pressing on the accelorator did nothing except exacerbate the symptoms.
While the car was running, the fuel pump ran conistently with no hessitation.
It was like the engine management system was struggling to keep the car running, revs going all over the place. It 'feels' like some sensor has gone haywire and giving out bad readings.
Eventually, after about 5 minutes the car stalled.
From then on it would start immediately but run rough for about 10 seconds then die. At one time it ran smooth, like all was well for about 10 seconds then died again. This happened for the next 10-15 minutes, at which time I could'nt find a simple fix....next the tow back home.
Any ideas as to where I can start looking or has anyone had this problem before? Any help woul be greatly appreciated.
started to loose power on my way home. I managed to park in a side street where the revs fluctuated wildly almost stalling while the car was in 'Park'.Pressing on the accelorator did nothing except exacerbate the symptoms.
While the car was running, the fuel pump ran conistently with no hessitation.
It was like the engine management system was struggling to keep the car running, revs going all over the place. It 'feels' like some sensor has gone haywire and giving out bad readings.
Eventually, after about 5 minutes the car stalled.
From then on it would start immediately but run rough for about 10 seconds then die. At one time it ran smooth, like all was well for about 10 seconds then died again. This happened for the next 10-15 minutes, at which time I could'nt find a simple fix....next the tow back home.
Any ideas as to where I can start looking or has anyone had this problem before? Any help woul be greatly appreciated.
02-28-2003, 07:41 AM
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Hi Jim,
It doesn't sound like the classic LH brain failure, if that's any consolation !
When it runs rough after start, does it still not respond at all to the throttle ?
Could be the MAF if this is the case.
Temp sensor 2 is a common failure, it would make the car run very rich or very weak. Your car sounds as though it is running very rich.
Do you know the car well enough to run some checks, or do you need more information ?
It doesn't sound like the classic LH brain failure, if that's any consolation !
When it runs rough after start, does it still not respond at all to the throttle ?
Could be the MAF if this is the case.
Temp sensor 2 is a common failure, it would make the car run very rich or very weak. Your car sounds as though it is running very rich.
Do you know the car well enough to run some checks, or do you need more information ?
02-28-2003, 07:56 AM
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John, Glad to hear some positive news about the LH.
Not really responding to the throttle.
I'm no mechanic but if you've got any ideas I can follow them through. Wherev is the MAF and Temp.2
Your right about it running rich, I could detect a richer exhaust smell while in this state.
Thanks.
Not really responding to the throttle.
I'm no mechanic but if you've got any ideas I can follow them through. Wherev is the MAF and Temp.2
Your right about it running rich, I could detect a richer exhaust smell while in this state.
Thanks.
02-28-2003, 10:15 AM
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The problem could be either fuel or fire. If you lose one coil, you will be putting half the fuel into the exhaust unburned.
Check the coil wires, making sure that both ends are clean and plugged in correctly.
The temp II sensor tells the injection and the ignition the coolant temp. There are two independant sensors in a small retangular unit on the top front of the engine, under the cross-bar.
If the sensor is open (showing very cold temp), the engine will usually not start hot, and will run OK cold and poorly hot.
If the sensor is shorted (showing very hot temp), the engine will do OK hot, but will be tough to start and run when cold.
Make sure that the sensor wires harness is plugged in securely. There is a wire lock on the rectangular connector.
If the Temp II sensor is bad, you can usually get it home or to a shop. Start the car and drive until it starts giving problems, stop at a safe place, and jumper the harness pins to ground.
Check the coil wires, making sure that both ends are clean and plugged in correctly.
The temp II sensor tells the injection and the ignition the coolant temp. There are two independant sensors in a small retangular unit on the top front of the engine, under the cross-bar.
If the sensor is open (showing very cold temp), the engine will usually not start hot, and will run OK cold and poorly hot.
If the sensor is shorted (showing very hot temp), the engine will do OK hot, but will be tough to start and run when cold.
Make sure that the sensor wires harness is plugged in securely. There is a wire lock on the rectangular connector.
If the Temp II sensor is bad, you can usually get it home or to a shop. Start the car and drive until it starts giving problems, stop at a safe place, and jumper the harness pins to ground.
03-03-2003, 02:25 AM
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OK...Got back to the car next morning and it started as usual...perfectly. I have been driving the car for the last 2 days without a problem but I have ordered the Temp II sensor anyway. The manual says that if it plays up I can bridge the sensor lead as an emergency fix.....have'nt needed to yet.
03-03-2003, 02:51 AM
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Jim...
I read your post yesterday. Since it was a rare rainy afternoon here in the land of the mouse..I decided to take the car to Barnes & Noble, a large bookstore here in town.
On the way back, about 1/2 mile from my house, my '85 S2 5 Speed suddenly lost power, missed badly, and produced voluminus black smoke.
I managed to work the car to my house. When I finally stopped and jumped overboard, I noticed some thermal waves and smoke pouring from one of the catylitic converters!
Well, that night the car ran nearly perfect-I shure don't know what exactly happened-
I read your post yesterday. Since it was a rare rainy afternoon here in the land of the mouse..I decided to take the car to Barnes & Noble, a large bookstore here in town.
On the way back, about 1/2 mile from my house, my '85 S2 5 Speed suddenly lost power, missed badly, and produced voluminus black smoke.
I managed to work the car to my house. When I finally stopped and jumped overboard, I noticed some thermal waves and smoke pouring from one of the catylitic converters!
Well, that night the car ran nearly perfect-I shure don't know what exactly happened-
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03-03-2003, 03:45 AM
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Geez Normy,
That would scare the crap right out of me seeing smoke pouring from the cat's.
Anyone have any ideas on this one.
Jim,
Shark still running O.K...Did you order the Temp II sensor because you found it to be bad?
Tim Delarm
That would scare the crap right out of me seeing smoke pouring from the cat's.
Anyone have any ideas on this one.
Jim,
Shark still running O.K...Did you order the Temp II sensor because you found it to be bad?
Tim Delarm
03-03-2003, 05:22 AM
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Normy,
My car has NEVER let me down b4 so I it was a bit of a shock to the system.....If I got your symptoms I would have got heart failure!!! (Except I don't have the Cats.)
Tim,
No mate, the sensor appears to be OK but as it may be intermittent I did't want to take the gamble. BTW if you need one the Workshop Manual quotes the original BOSCH part No. 0280.130.032 for the s4 models...... cheap as chips.
My car has NEVER let me down b4 so I it was a bit of a shock to the system.....If I got your symptoms I would have got heart failure!!! (Except I don't have the Cats.)
Tim,
No mate, the sensor appears to be OK but as it may be intermittent I did't want to take the gamble. BTW if you need one the Workshop Manual quotes the original BOSCH part No. 0280.130.032 for the s4 models...... cheap as chips.
03-03-2003, 02:19 PM
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Hi Jim,
It's a good idea to change the Temp sensor 2.
Several of the UK specialists change them as a precaution on their customers' cars every 30k miles or so as part of preventative maintainance.
Also, check your coil and plug wires/connections out, as Wally suggested. They can often cause problems, especially in damp conditions.
It's a good idea to change the Temp sensor 2.
Several of the UK specialists change them as a precaution on their customers' cars every 30k miles or so as part of preventative maintainance.
Also, check your coil and plug wires/connections out, as Wally suggested. They can often cause problems, especially in damp conditions.
03-03-2003, 02:25 PM
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Well, if you like carrying around an extra Temp II, you might want to invest in an extra fuel pump relay.
They are a bit more expensive, but when it went on my car, I got exactly the same symptoms, but the fuel pump also died. I forget if the LH brain also has a realy controling the power to it. I would assume so, might want to carry around an extra one of those too.
A extra relay, or jumper. Jumper's cheaper, relay's safer.
They are a bit more expensive, but when it went on my car, I got exactly the same symptoms, but the fuel pump also died. I forget if the LH brain also has a realy controling the power to it. I would assume so, might want to carry around an extra one of those too.
A extra relay, or jumper. Jumper's cheaper, relay's safer.
03-04-2003, 01:44 AM
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Latest update, car broke down again, same symptoms. I'm waiting for the TempII sensor to arrive. I also found that there is a 3 pin black connector roughly opposite Temp II and mounted towards the front of the block (Black..Yellow...Earth cables) which appeared to be shorting. Cut the connector off which was crumbling and temporarily re connected the wires while ordering the correct connector plug.
Prior to doing this I had unplugged TempII but car was still running rough then stalling. After about 5 min. it started running smoothly again.
I'm not sure if it takes the LH brain a few minutes to re adjust to the changed signal and then run smoother or it was just coincidence. Anyway all started running ok sfter this procedure.
(Just a note: I tried bridging the TempII cable and then tried earthing but it made no difference....again....unless I'm supposed to wait for a few minutes first which I did'nt do.
Tommy 928,
Checked they seem to be ok.
Prior to doing this I had unplugged TempII but car was still running rough then stalling. After about 5 min. it started running smoothly again.
I'm not sure if it takes the LH brain a few minutes to re adjust to the changed signal and then run smoother or it was just coincidence. Anyway all started running ok sfter this procedure.
(Just a note: I tried bridging the TempII cable and then tried earthing but it made no difference....again....unless I'm supposed to wait for a few minutes first which I did'nt do.
Tommy 928,
Checked they seem to be ok.
03-04-2003, 08:36 PM
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Jim.
Just took a look at your message about "Loss of Power then Rough Idle...then Stall...." My 86 s was doing the same exact thing about two years ago. I took it to my Porsche Mechanic and they had discovered that the O2 Sensor was fouled up and that in turn made my air/fuel mixture rich, causing my plugs to foul up. To match up what mine did and your problem here is what mine was doing.
When I would start the car it would take 2-3 cranks before I could get it to fire. After the engine started it would run rough. Like the fuel wasn't getting to the engine. When I would bring up the RPM's and let off the throttle the RPM's would drop drastically and jump again. If I didn't get back on the throttle fast enough the car would stall. If I drove the car and pushed in the clutch to switch gears RPM's would drop and rise.
If this is detailed to what your 928 is doing take a look into the 02 Sensor. It wouldn't hurt to replace it. about $70-$200 at 928 International.
Michael Robinson
86 928s
87 928s4
Just took a look at your message about "Loss of Power then Rough Idle...then Stall...." My 86 s was doing the same exact thing about two years ago. I took it to my Porsche Mechanic and they had discovered that the O2 Sensor was fouled up and that in turn made my air/fuel mixture rich, causing my plugs to foul up. To match up what mine did and your problem here is what mine was doing.
When I would start the car it would take 2-3 cranks before I could get it to fire. After the engine started it would run rough. Like the fuel wasn't getting to the engine. When I would bring up the RPM's and let off the throttle the RPM's would drop drastically and jump again. If I didn't get back on the throttle fast enough the car would stall. If I drove the car and pushed in the clutch to switch gears RPM's would drop and rise.
If this is detailed to what your 928 is doing take a look into the 02 Sensor. It wouldn't hurt to replace it. about $70-$200 at 928 International.
Michael Robinson
86 928s
87 928s4
03-04-2003, 09:25 PM
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I just finished fixing a similiar issue on my 82. It ran great and then decided one day to start having intermittant problems as you say. I would pump the gas to keep her going, but would see nasty dark gray smoke coming out the exhaust until it finally decided to clear it's throat and then ran like a charm. Turned out that was not the problem.
After a short mental process of elimination and a discussion or two with more knowledgable folks, I took the time to clean all major electrical contact points under the hood and at the battery. Included was the coil posts and resistor blocks. Checked all wires for wear. Basically, I had a list of about 15-20 things that I cleaned and checked.
The car runs perfect again.
I have learned that it is true when anyone says to clean all electrical connections FIRST before moving to the next diagnosis/guess. It certainly is the cheapest route, if not the fastest way to the next step short of success.
After a short mental process of elimination and a discussion or two with more knowledgable folks, I took the time to clean all major electrical contact points under the hood and at the battery. Included was the coil posts and resistor blocks. Checked all wires for wear. Basically, I had a list of about 15-20 things that I cleaned and checked.
The car runs perfect again.
I have learned that it is true when anyone says to clean all electrical connections FIRST before moving to the next diagnosis/guess. It certainly is the cheapest route, if not the fastest way to the next step short of success.
