Power Loss issue
04-28-2010, 09:45 PM
#1
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Power Loss issue
Here is the problem I am having with my 1982 944 NA.
The following has already been done:
Replaced with new cap, new rotor, new wires, new spark plugs, cleaned injectors by WitchHunter, New Vacum lines and new battery. J-Boot has been check for splits. Replaced AFM and computer with know good units. One reference sensor replaced with know good one. The speed sensor checks out good as per Clarks Garage specs. New belts and water pump too.
When Cold: Car idles well. Driving the car there is a hesitation at 1900 - 2200 RPM and it backfires in the exhaust. Past 2200 RPM the car has tememdous power and jumps easily to redline.
When at operating temp: Car idles well. Step on the gas pedal and it seems like there is a hugh vacum leak. Cannot get the RPMs to come up, even out of gear.
Ideas?
The following has already been done:
Replaced with new cap, new rotor, new wires, new spark plugs, cleaned injectors by WitchHunter, New Vacum lines and new battery. J-Boot has been check for splits. Replaced AFM and computer with know good units. One reference sensor replaced with know good one. The speed sensor checks out good as per Clarks Garage specs. New belts and water pump too.
When Cold: Car idles well. Driving the car there is a hesitation at 1900 - 2200 RPM and it backfires in the exhaust. Past 2200 RPM the car has tememdous power and jumps easily to redline.
When at operating temp: Car idles well. Step on the gas pedal and it seems like there is a hugh vacum leak. Cannot get the RPMs to come up, even out of gear.
Ideas?
04-29-2010, 04:04 AM
#3
Burning Brakes
good description 
do I take it that the car doesn't behave like it has a huge vacumn leak when cold ,yes?
Your description would suggest a fuel delivery problem .However I am not familiar with the cold start system on early cars. (Late cars they have an additional injector.)
As Yarf says a good place to start is to check the wiring and replace the DME temperature sensor. They are not expensive and it would eliminate that.
Have you tried running the car with a fuel pressure guage connected ? Just to make sure you are not getting variable fuel pressure.
do I take it that the car doesn't behave like it has a huge vacumn leak when cold ,yes?
Your description would suggest a fuel delivery problem .However I am not familiar with the cold start system on early cars. (Late cars they have an additional injector.)
As Yarf says a good place to start is to check the wiring and replace the DME temperature sensor. They are not expensive and it would eliminate that.
Have you tried running the car with a fuel pressure guage connected ? Just to make sure you are not getting variable fuel pressure.
05-01-2010, 04:26 PM
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OK, Temp sensor was replaced with no difference. 
The original tested good, but changed it anyway, since it looked original.
When it is cold, there is a miss around 1900-2200RPM and it backfires in the exhaust, but otherwise runs fine thru the remaing RPM range.
As soon as it reaches operating temp...... no power. Give it gas, it will stall. Idles just find when at operating temp.
Exhaust smells very rich all the time.
Problem started after the car ran out of gas. I was just about ready to register the car and put it on the road, then this problem.
I can't change the fuel filter as the fitting are so rusted they won't come loose.
I have been hitting the fittings with PB Blaster for 2+ weeks and they don't budge.
I won't dare take any heat to them, since it is the gas line.
The original tested good, but changed it anyway, since it looked original.When it is cold, there is a miss around 1900-2200RPM and it backfires in the exhaust, but otherwise runs fine thru the remaing RPM range.
As soon as it reaches operating temp...... no power. Give it gas, it will stall. Idles just find when at operating temp.
Exhaust smells very rich all the time.
Problem started after the car ran out of gas. I was just about ready to register the car and put it on the road, then this problem.
I can't change the fuel filter as the fitting are so rusted they won't come loose.
I have been hitting the fittings with PB Blaster for 2+ weeks and they don't budge.
I won't dare take any heat to them, since it is the gas line.
05-01-2010, 05:44 PM
#6
Burning Brakes
this definitely doesn't sound like a blocked filter problem. It sounds like you're getting too much fuel not insufficient.
The fact that you only get this problem when hot should narrow down the culpret considerably.
Its either a temperature sensor reading faulty or something mechanical that influences the fuel mixture being effected by heat ie AFM ?
I believe there are two temperature sensors involved in the Bosch system an air inlet sensor and a coolant temperature sensor
Which did you check and replace ?
. There is also an oxygen sensor .?
I think you need to attach a fuel pressure gauge to see what the fuel pressure is doing whilst the engine is running.
The fact that you only get this problem when hot should narrow down the culpret considerably.
Its either a temperature sensor reading faulty or something mechanical that influences the fuel mixture being effected by heat ie AFM ?
I believe there are two temperature sensors involved in the Bosch system an air inlet sensor and a coolant temperature sensor
Which did you check and replace ?
. There is also an oxygen sensor .?
I think you need to attach a fuel pressure gauge to see what the fuel pressure is doing whilst the engine is running.
