Finally... Voltage Dip and Engine Stumble Solved!
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Finally... Voltage Dip and Engine Stumble Solved!
After researching this issue for the past 6 months, I finally found the solution (or so it appears so far).
I was experiencing 3 major problems which I assumed were related:
(1) DIC and Voltage Gauge reporting lower voltage than actual voltage (as verified on DMM).
(2) Voltage Drop when coming to a stop (actually dipping sometimes more than 1-1/2 volts when RPM fell below 800 RPM and the quicker the deceleration usually the further the dip - it was also dipping in PARK if I punched the accelerator and let off quickly - in both cases the voltage would usually recover shortly)
(3) Car would sometimes start shaking and rattling when coming to a stop (letting up on brake and letting the car roll a few inches usually helped recover)
Things I tried (in order):
Checking/Cleaning All Grounds
New Alternator
New Battery
New Ignition Switch
New Belts/Pulleys/Tensioners/Idlers
New Starter (and new engine - unrelated)
After all the above, I was out of ideas. I got my car back from the Dealership with the new engine last Friday and all the problems listed above still persisted!
Today, I took the car back to the Dealership and asked a couple Master Mechanics (the same two that replaced my engine) if they had any idea what might be causing my voltage symptoms. As soon as I explained my symptoms, both mechanics said in unison "sounds like throttle body valve is sticking!". They said that would throw the voltage signal off if it were not closing fast enough.
I had noticed that when the engine was being replaced and the throttle body was being transferred to the new engine that there was a small amount of black soot at both the top and bottom edge of the butterfly. I assumed (incorrectly) that they would clean that as a routine procedure (not so). So this afternoon I pulled the air coupler and sprayed Berryman's Chemtool into the throttle opening and wiped out what I could of the black buildup. Took the car for a one hour drive and problems 2 and 3 disappeared. Car now does not dip but sometime .1 - .2 volts, immediately recovers and the car no longer shakes and rattles when coming to a stop or putting it in reverse! Smooth as glass now!
I am guessing the the black buildup on the throttle plate is coming from oil dislodging from the Hurricane (oil type) air filter element over time. It was a small amount and took a couple years in my case to start showing symptoms, but that is my best guess - just enough to gunk-up the throttle action when trying to close completely.
Anyway, it appears that after spending well over $1000 on new parts that all needed was a rag and some carburetor cleaner!
I appreciate all the help from the many forum members that made suggestions on this issue - they all made good sense and I am not sorry that I replaced all the parts shown above since after 8 years it probably needed them anyway.
The first problem of the DIC and Voltage guage not being accurate is obviously still there, but that is just a nuisance - still looking for a fix for that.
I was experiencing 3 major problems which I assumed were related:
(1) DIC and Voltage Gauge reporting lower voltage than actual voltage (as verified on DMM).
(2) Voltage Drop when coming to a stop (actually dipping sometimes more than 1-1/2 volts when RPM fell below 800 RPM and the quicker the deceleration usually the further the dip - it was also dipping in PARK if I punched the accelerator and let off quickly - in both cases the voltage would usually recover shortly)
(3) Car would sometimes start shaking and rattling when coming to a stop (letting up on brake and letting the car roll a few inches usually helped recover)
Things I tried (in order):
Checking/Cleaning All Grounds
New Alternator
New Battery
New Ignition Switch
New Belts/Pulleys/Tensioners/Idlers
New Starter (and new engine - unrelated)
After all the above, I was out of ideas. I got my car back from the Dealership with the new engine last Friday and all the problems listed above still persisted!
Today, I took the car back to the Dealership and asked a couple Master Mechanics (the same two that replaced my engine) if they had any idea what might be causing my voltage symptoms. As soon as I explained my symptoms, both mechanics said in unison "sounds like throttle body valve is sticking!". They said that would throw the voltage signal off if it were not closing fast enough.
I had noticed that when the engine was being replaced and the throttle body was being transferred to the new engine that there was a small amount of black soot at both the top and bottom edge of the butterfly. I assumed (incorrectly) that they would clean that as a routine procedure (not so). So this afternoon I pulled the air coupler and sprayed Berryman's Chemtool into the throttle opening and wiped out what I could of the black buildup. Took the car for a one hour drive and problems 2 and 3 disappeared. Car now does not dip but sometime .1 - .2 volts, immediately recovers and the car no longer shakes and rattles when coming to a stop or putting it in reverse! Smooth as glass now!
I am guessing the the black buildup on the throttle plate is coming from oil dislodging from the Hurricane (oil type) air filter element over time. It was a small amount and took a couple years in my case to start showing symptoms, but that is my best guess - just enough to gunk-up the throttle action when trying to close completely.
Anyway, it appears that after spending well over $1000 on new parts that all needed was a rag and some carburetor cleaner!
I appreciate all the help from the many forum members that made suggestions on this issue - they all made good sense and I am not sorry that I replaced all the parts shown above since after 8 years it probably needed them anyway.
The first problem of the DIC and Voltage guage not being accurate is obviously still there, but that is just a nuisance - still looking for a fix for that.
Last edited by Choreo; Nov 18, 2008 at 05:22 AM.
to fix a problem that you felt was never going away!?!?
Awesome! Congrats on solving your problems!
- Jason
....Should be ready for lots of more miles now 
