Engine revs correctly with EST plug unconnected?
Thread Starter
Acct suspended by request 12 Dec 2012
Joined: Sep 2007
Posts: 94
Likes: 1
From: Louisville KY
Engine revs correctly with EST plug unconnected?
Hello All.
1989, stock 350. Just installed New Accel Distributor (not mechanical advance) .
Engine stumbles and misses badly starting at about 1500 rpms Set timing with EST harness unplugged. 6 degrees right on.
Noticed however that the car accelerates well with no miss if I leave the EST harness unplugged. As soon as I reconnect harness, after resetting computer by disconnecting battery, get severe roughness again starting at about 1500.
What would cause this problem to go away by leaving the EST disconnected?
Thanks
1989, stock 350. Just installed New Accel Distributor (not mechanical advance) .
Engine stumbles and misses badly starting at about 1500 rpms Set timing with EST harness unplugged. 6 degrees right on.
Noticed however that the car accelerates well with no miss if I leave the EST harness unplugged. As soon as I reconnect harness, after resetting computer by disconnecting battery, get severe roughness again starting at about 1500.
What would cause this problem to go away by leaving the EST disconnected?
Thanks
Last edited by wa4ky; Aug 16, 2009 at 09:14 PM.
Thread Starter
Acct suspended by request 12 Dec 2012
Joined: Sep 2007
Posts: 94
Likes: 1
From: Louisville KY
I wanted to try a new distributor, because I have been fighting an intermittent miss for over a year. Can feel it best at idle. Have replaced a multitude of things and has been to several expert shops.
Anyway, the replacement is Accel p/n 59109. Supposed to be correct.
Really strange, with the EST connected, the intermittent miss is not as bad, but acceleration falls apart about 1500..
With the EST disconnected, it runs well up through the rpms, but then the intermittant miss comes back. I feel like I am fighting two things now, as I did not have the heavy fluttering with the old distributor, only the slight miss.
Make any sense?
OK, PUMP THE OEM DISTRIBUTOR BACK IN , TIMED IT AND IT NOW ACCELERATES THROUGH THE RPMS PERFECTLY AGAIN. SOMETHING ABOUT THE ACCEL DISTRIBUTOR DOES NOT WORK WITH THIS COMPUTER. SO I AM BACK TO JUST THE ORIGINAL PROBLEM OF A INTERMITTANT STUMBLE FELT BEST AT IDLE. I THINK A LOT OF C4'S HAVE THIS ACCORDING TO THE POSTS AND I HAVE NEVER SEEN ANYONE LIST A DEFINITE CURE OUTSIDE OF NEW INJECTORS, WHICH I HAVE. THANKS GUYS.
Anyway, the replacement is Accel p/n 59109. Supposed to be correct.
Really strange, with the EST connected, the intermittent miss is not as bad, but acceleration falls apart about 1500..
With the EST disconnected, it runs well up through the rpms, but then the intermittant miss comes back. I feel like I am fighting two things now, as I did not have the heavy fluttering with the old distributor, only the slight miss.
Make any sense?
OK, PUMP THE OEM DISTRIBUTOR BACK IN , TIMED IT AND IT NOW ACCELERATES THROUGH THE RPMS PERFECTLY AGAIN. SOMETHING ABOUT THE ACCEL DISTRIBUTOR DOES NOT WORK WITH THIS COMPUTER. SO I AM BACK TO JUST THE ORIGINAL PROBLEM OF A INTERMITTANT STUMBLE FELT BEST AT IDLE. I THINK A LOT OF C4'S HAVE THIS ACCORDING TO THE POSTS AND I HAVE NEVER SEEN ANYONE LIST A DEFINITE CURE OUTSIDE OF NEW INJECTORS, WHICH I HAVE. THANKS GUYS.
Last edited by wa4ky; Aug 16, 2009 at 09:19 PM. Reason: Problem solved
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Could use a little more detail: Is it ok cold? Does it only fall apart when you floor it? How severe is the miss? Have you checked valve timing/compression? Generally, with the EST disconnected it's set a trouble code (42), so it's running on backup; ie, input from the O2 is ignored and fuel is delivered from preset tables burned into the Chip. So if it isn't running right when there isn't a Code, you'd suspect that some sort of garbage is tricking the O2 (or some other sensor) and with the wrong sensor input, the ECM can't deliver the correct amount of fuel so it runs like crap. Start by scanning it to see what it's trying to do and then post that data so that we can tell you what to look for.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
You might also try leaving the distributor hooked up and disconnecting the MAF (since that signal is used to calculate Load which is used when it accelerates). If it goes away, you need a new one. As to the miss - check for a leaking head gasket at #7 - especially since it's an '89.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I wanted to try a new distributor, because I have been fighting an intermittent miss for over a year. Can feel it best at idle. Have replaced a multitude of things and has been to several expert shops.
Anyway, the replacement is Accel p/n 59109. Supposed to be correct.
Really strange, with the EST connected, the intermittent miss is not as bad, but acceleration falls apart about 1500..
With the EST disconnected, it runs well up through the rpms, but then the intermittant miss comes back. I feel like I am fighting two things now, as I did not have the heavy fluttering with the old distributor, only the slight miss.
Make any sense?
OK, PUMP THE OEM DISTRIBUTOR BACK IN , TIMED IT AND IT NOW ACCELERATES THROUGH THE RPMS PERFECTLY AGAIN. SOMETHING ABOUT THE ACCEL DISTRIBUTOR DOES NOT WORK WITH THIS COMPUTER. SO I AM BACK TO JUST THE ORIGINAL PROBLEM OF A INTERMITTANT STUMBLE FELT BEST AT IDLE. I THINK A LOT OF C4'S HAVE THIS ACCORDING TO THE POSTS AND I HAVE NEVER SEEN ANYONE LIST A DEFINITE CURE OUTSIDE OF NEW INJECTORS, WHICH I HAVE. THANKS GUYS.
Anyway, the replacement is Accel p/n 59109. Supposed to be correct.
Really strange, with the EST connected, the intermittent miss is not as bad, but acceleration falls apart about 1500..
With the EST disconnected, it runs well up through the rpms, but then the intermittant miss comes back. I feel like I am fighting two things now, as I did not have the heavy fluttering with the old distributor, only the slight miss.
Make any sense?
OK, PUMP THE OEM DISTRIBUTOR BACK IN , TIMED IT AND IT NOW ACCELERATES THROUGH THE RPMS PERFECTLY AGAIN. SOMETHING ABOUT THE ACCEL DISTRIBUTOR DOES NOT WORK WITH THIS COMPUTER. SO I AM BACK TO JUST THE ORIGINAL PROBLEM OF A INTERMITTANT STUMBLE FELT BEST AT IDLE. I THINK A LOT OF C4'S HAVE THIS ACCORDING TO THE POSTS AND I HAVE NEVER SEEN ANYONE LIST A DEFINITE CURE OUTSIDE OF NEW INJECTORS, WHICH I HAVE. THANKS GUYS.
