Running rough
02-07-2005, 05:05 PM
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Running rough
My '88 911 cab is running rough.
SYMPTOMS: idle is fine, from first to second is appears to be missing between 2200-2500 RPM after that it seems ok.
Cause & repair:
1. fuel filter -changed a year ago -
2. New plug wires could have one screwed up
3. Oxygen sensor....maybe
4. dme POSSIBLY
5. Vaccum hose?
6. Plugs just cleaned them all
7. Air filter - K&N its fine.
8.distributer new a year ago
9. All fuel lines just changed
This is driving me nuts any suggestions...thanks..bob
SYMPTOMS: idle is fine, from first to second is appears to be missing between 2200-2500 RPM after that it seems ok.
Cause & repair:
1. fuel filter -changed a year ago -
2. New plug wires could have one screwed up
3. Oxygen sensor....maybe
4. dme POSSIBLY
5. Vaccum hose?
6. Plugs just cleaned them all
7. Air filter - K&N its fine.
8.distributer new a year ago
9. All fuel lines just changed
This is driving me nuts any suggestions...thanks..bob
02-08-2005, 02:41 AM
#2
RL Technical Advisor
Bob:
First, when did it first start running rough? After a fuel fill-up? All by itself? Does this happen at light throttle or when you boot it?
Here are some things to check VERY thoroughly. Assume nothing!!!!
1) If you got a bad batch of fuel, chnage the filter again.
2) Carefully inspect the cap & rotor for any cracks, carbon tracks or arcing.
3) Check the plug connectors with a VOM. Those Beru connectors are very troublesome.
4) Check firing order at distributor cap and make certain that each plug wire is connected to the proper cylinder.
4) If the oxysensor is more than 50K old, change it. These can be checked with a good VOM to watch how fast it cycles.
5) Check the entire intake, especially around the manifold flanges and any rubber joint for vacuum leaks. Use a can of carb cleaner. False air makes for lean running and that creates misses.
6) Check the alternator/VR for proper operation. Use the VOM at the battery terminals and make sure you have 13.8-14.4 v at 2000 RPM.
Please let me know what you find.
First, when did it first start running rough? After a fuel fill-up? All by itself? Does this happen at light throttle or when you boot it?
Here are some things to check VERY thoroughly. Assume nothing!!!!
1) If you got a bad batch of fuel, chnage the filter again.
2) Carefully inspect the cap & rotor for any cracks, carbon tracks or arcing.
3) Check the plug connectors with a VOM. Those Beru connectors are very troublesome.
4) Check firing order at distributor cap and make certain that each plug wire is connected to the proper cylinder.
4) If the oxysensor is more than 50K old, change it. These can be checked with a good VOM to watch how fast it cycles.
5) Check the entire intake, especially around the manifold flanges and any rubber joint for vacuum leaks. Use a can of carb cleaner. False air makes for lean running and that creates misses.
6) Check the alternator/VR for proper operation. Use the VOM at the battery terminals and make sure you have 13.8-14.4 v at 2000 RPM.
Please let me know what you find.
02-10-2005, 11:30 PM
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Bob
With all due hommage to Steve W, another thought, because I had similar problems, though mine, was more along the lines of a rough idle, misses and slow throttle response on my 84. I also use a K&N filter. Over zealous re-oiling and not allowing adequate "set time" over a few years, lead to what I beleive was purple oil and dirt on my MAF (mass air flow sensor). I discovered this after many $ and hours spent on parts(fuel injectors, filters, etc) and red herring trails. I sprayed some Intake Cleaner (not carb cleaner, though same shelf and similar spray container at your local auto parts place). My problem immediately vanished. Probably worth a try for $5 or $6. regards,
Steve
With all due hommage to Steve W, another thought, because I had similar problems, though mine, was more along the lines of a rough idle, misses and slow throttle response on my 84. I also use a K&N filter. Over zealous re-oiling and not allowing adequate "set time" over a few years, lead to what I beleive was purple oil and dirt on my MAF (mass air flow sensor). I discovered this after many $ and hours spent on parts(fuel injectors, filters, etc) and red herring trails. I sprayed some Intake Cleaner (not carb cleaner, though same shelf and similar spray container at your local auto parts place). My problem immediately vanished. Probably worth a try for $5 or $6. regards,
Steve
