Bad Gas mileage, lots of smoke, and a horrible smell.
01-18-2005, 12:25 AM
#31
Lazer Beam Shooter
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Thread Starter
Well the gas light went on, right as it did i put 5 dollars in. That got me at least 2 gallons, more toward 3.
I dont have a speedometer so I dont know exactly.
Drove 5 miles to the movies and 5 miles back.
Drove around for 10 minutes after that, gas lights back on.
20 miles? If that? I watch my little MPG thing, and it NEVER stays above the 20 line, its almost always in the end, even under light acceleration. Basically, to keep the car moving at a constant speed, it has to be in the danger zone on the MPG meter thing, chipped or unchipped.
Ive tried running 87,89,93 octane. Nothing. Im punching myself in the ***** on this. I have got so much to do to the car and this pops up. Its never ending
My car has never idled right. Ever. Its always been hard to start up too. Im running down the list of stuff thats causing this, and now im down to Fuel Delivery, and then the DME sensing stuff.
I dont have a speedometer so I dont know exactly.
Drove 5 miles to the movies and 5 miles back.
Drove around for 10 minutes after that, gas lights back on.
20 miles? If that? I watch my little MPG thing, and it NEVER stays above the 20 line, its almost always in the end, even under light acceleration. Basically, to keep the car moving at a constant speed, it has to be in the danger zone on the MPG meter thing, chipped or unchipped.
Ive tried running 87,89,93 octane. Nothing. Im punching myself in the ***** on this. I have got so much to do to the car and this pops up. Its never ending
My car has never idled right. Ever. Its always been hard to start up too. Im running down the list of stuff thats causing this, and now im down to Fuel Delivery, and then the DME sensing stuff.
01-18-2005, 01:16 AM
#33
Lazer Beam Shooter
Rennlist Member
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Thread Starter
Bwahahah DME relay. I have one of those too
I DUNNO IF I CAN MAKE IT SATURDAY. I have to try my *** off to get somebody to work for me. I must!
I DUNNO IF I CAN MAKE IT SATURDAY. I have to try my *** off to get somebody to work for me. I must!
Its my first SOW GTG!
01-18-2005, 01:50 AM
#35
Race Director
"I was wondering, would a bad fuel pressure regulator cause the car to idle rough intermittenly?"
Yes most definitely. The FPR is controlled by vacuum from the intake-manifold. So at idle, and partial-throttle running, 10-20 in.Hg. will reduce fuel-pressure by 30-60% less than the pressure-rating of the FPR. So the FPR is rated at 38psi and at idle, the vacuum line will reduce fuel-pressure to about 25psi. Only under full-throttle with very little vacuum will the FPR deliver full pressure.
So, very, very common problem is the vacuum Ts that hold all the vacuum lines together. They either slip off the vacuum line, or they slip enough to reduce vacuum without looking like a leak. Or the Ts themselves crack at the intersection and you can't see it unless you flex the joints. Best way to check is to hook up a vacuum gauge at each and every device using vacuum and the vacuum reading should be identical. Through process of elimination and deductive reasoning, you can figure out where the leak is based upon 5-6 readings at different places in the engine.
Yes most definitely. The FPR is controlled by vacuum from the intake-manifold. So at idle, and partial-throttle running, 10-20 in.Hg. will reduce fuel-pressure by 30-60% less than the pressure-rating of the FPR. So the FPR is rated at 38psi and at idle, the vacuum line will reduce fuel-pressure to about 25psi. Only under full-throttle with very little vacuum will the FPR deliver full pressure.
So, very, very common problem is the vacuum Ts that hold all the vacuum lines together. They either slip off the vacuum line, or they slip enough to reduce vacuum without looking like a leak. Or the Ts themselves crack at the intersection and you can't see it unless you flex the joints. Best way to check is to hook up a vacuum gauge at each and every device using vacuum and the vacuum reading should be identical. Through process of elimination and deductive reasoning, you can figure out where the leak is based upon 5-6 readings at different places in the engine.
01-18-2005, 02:01 AM
#36
Nordschleife Master
Good to know Danno, i will poke around at the vacuum lines when i can get under the hood again this weekend. Would it be worthwhile to just replace the FPR anyway?
01-20-2005, 04:33 PM
#37
Lazer Beam Shooter
Rennlist Member
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Thread Starter
This is actually a new problem, maybe due to the cold? Does the engine sense air temperature?
IT gets horrible gas mileage Chipped or not. It used to get pretty good mileage before... im gonna try legolands thingy today.
IT gets horrible gas mileage Chipped or not. It used to get pretty good mileage before... im gonna try legolands thingy today.
01-20-2005, 05:24 PM
#38
Three Wheelin'
Rock:
I "beta tested" one of FR's early chips, and it never made the engine in my '84 run rich.
Even though FR's newer chips ignore the O2 sensor, you can still take voltage readings from the sensor with a digital meter. With that said, I highly recommend going back to a chip that DOES use the O2 sensor.
With a working O2 sensor you should see it's output voltage vary or dither across 0.50 volts. Higher is rich, lower is lean.
To check the AFM I would start with the temp sensor. This sensor sees incoming air temp and sends an input to the DME. The DME takes this air temp and uses it to compute air density, and then uses air density to compute volumetric air flow, which is the prime indication of engine load. Engine load is then used to compute injector duty cycle (how long the injectors stay open), and O2 sensor output is used to "tweak" injector duty cycle to maintain the proper fuel/air ratio.
The easiest way to check the air temp sensor is to pop the cover off of the AFM (you can seal it back with some RTV), remove the rubber intake boot, connect an ohm meter to the sensor leads, and then hold an ice cube against the sensor. The sensor is an NTC, or Negative Temperature coefficient device, so you should see the sensor's resistance go up as the sensor cools off.
Besides wasting fuel, running rich has some other downsides. First off, running rich shortens the life span of the O2 sensor. Second, running rich will destory and clog the CAT, which causes exhaust back pressure to increase, which robs power. Third, running rich causes carbon to build up in the cylinders and on the spark plugs. This carbon build up changes the compression ratio and can lead to hot spots in the combustion chamber.
As for the MPG gage, it is telling you that the injector duty cycle is WAY to long, which is an indication that the DME does not have accurate engine load data. This can be caused by vacuum leaks, bad O2 sensor, bad DME Temp sensor (the one with the blue connector), or a bad or misadjusted AFM.
Speaking of the AFM: If you decide to "tweak" the flapper spring (that is what the black "gear" is for), I highly recommend putting a dwell/tach on the coil and a DVM on the O2 sensor. With these connected you can watch engine RPM and the mixture so you don't go too lean. When you "tweak" the flapper spring, do it one or two "clicks" at a time and then check the DVM. As you do this you should discover that there is a fairly narrow band where the engine will idle. Go to far one way or the other and the engine will stumble and start to die.
Final word of caution: Do some studying before you start. You need to know how the DME controls the engine, and you need to know what to expect when you start "tweaking." I HIGHLY recommend, and STRONGLY advise getting a copy of "Motronic Engine Management." I got my copy from Performance Products, and I believe the ISDN is 1 987 722 161. This technical instruction manual covers the entire engine management system from spark plugs, to injectors, and even discusses the basics of vario-cam systems.
I "beta tested" one of FR's early chips, and it never made the engine in my '84 run rich.
Even though FR's newer chips ignore the O2 sensor, you can still take voltage readings from the sensor with a digital meter. With that said, I highly recommend going back to a chip that DOES use the O2 sensor.
With a working O2 sensor you should see it's output voltage vary or dither across 0.50 volts. Higher is rich, lower is lean.
To check the AFM I would start with the temp sensor. This sensor sees incoming air temp and sends an input to the DME. The DME takes this air temp and uses it to compute air density, and then uses air density to compute volumetric air flow, which is the prime indication of engine load. Engine load is then used to compute injector duty cycle (how long the injectors stay open), and O2 sensor output is used to "tweak" injector duty cycle to maintain the proper fuel/air ratio.
The easiest way to check the air temp sensor is to pop the cover off of the AFM (you can seal it back with some RTV), remove the rubber intake boot, connect an ohm meter to the sensor leads, and then hold an ice cube against the sensor. The sensor is an NTC, or Negative Temperature coefficient device, so you should see the sensor's resistance go up as the sensor cools off.
Besides wasting fuel, running rich has some other downsides. First off, running rich shortens the life span of the O2 sensor. Second, running rich will destory and clog the CAT, which causes exhaust back pressure to increase, which robs power. Third, running rich causes carbon to build up in the cylinders and on the spark plugs. This carbon build up changes the compression ratio and can lead to hot spots in the combustion chamber.
As for the MPG gage, it is telling you that the injector duty cycle is WAY to long, which is an indication that the DME does not have accurate engine load data. This can be caused by vacuum leaks, bad O2 sensor, bad DME Temp sensor (the one with the blue connector), or a bad or misadjusted AFM.
Speaking of the AFM: If you decide to "tweak" the flapper spring (that is what the black "gear" is for), I highly recommend putting a dwell/tach on the coil and a DVM on the O2 sensor. With these connected you can watch engine RPM and the mixture so you don't go too lean. When you "tweak" the flapper spring, do it one or two "clicks" at a time and then check the DVM. As you do this you should discover that there is a fairly narrow band where the engine will idle. Go to far one way or the other and the engine will stumble and start to die.
Final word of caution: Do some studying before you start. You need to know how the DME controls the engine, and you need to know what to expect when you start "tweaking." I HIGHLY recommend, and STRONGLY advise getting a copy of "Motronic Engine Management." I got my copy from Performance Products, and I believe the ISDN is 1 987 722 161. This technical instruction manual covers the entire engine management system from spark plugs, to injectors, and even discusses the basics of vario-cam systems.
