Sudden Loss of Power at Around 3200 RPM - Alfa Romeo Bulletin Board & Forums
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 06-14-2016, 04:21 AM Thread Starter
Registered User
 
Join Date: Sep 2015
Location: Newton, MA USA
Posts: 46
Garage
Sudden Loss of Power at Around 3200 RPM

I have a 1974 Spider SPICA and I am seeing a sudden loss of power at around 3200 RPM. The car starts up fine but as I reach around 3000 RPM, there is a consistent jerking, lurching loss of power feeling as shown in the below video.

The problem started a month or so ago and was intermittent. It has become worse now and happens all the time. It may have started shortly after I installed a new Centerline electronic distributor (ID405). Initially, the car did run well with it. I timed it with a strobe using the "P" mark at idle. I'm not sure the distributor is the issue.

The fuel filters were both replaced a few months ago and the low fuel pressure light which pulses on briefly at the initial key turn, does not come on when this problem occurs.

I have adjusted the SPICA thermostatic actuator screw and turned the FCS to try to lean out a smokey carbon exhaust. Not sure if this could be related.

Does anyone have any idea what's going on?

Video link showing problem:
ihart is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 06-14-2016, 05:17 AM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,768
It could be your coil or plug wires or distributor cap/rotor. It is hard to test them but they are inexpensive to replace.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is online now  
post #3 of 11 (permalink) Old 06-14-2016, 06:07 AM Thread Starter
Registered User
 
Join Date: Sep 2015
Location: Newton, MA USA
Posts: 46
Garage
Thanks Ed, I forgot to mention that the coil is brand new. It is a Bosch Blue coil. I did not add back in the resistor that was on the 42 year old original coil.
The distributor cap and rotor are brand new and came with the Centerline ID405 distributor.
The wires were installed by the PO. I could definitely try new ones as this might be an issue.

Does this smell like a distributor/spark problem and not a SPICA issue of some sort? Could it be that I timed the distributor at the idle "P" mark rather than at the 5000 RPM "M" mark?
ihart is offline  
Sponsored Links
Advertisement
 
post #4 of 11 (permalink) Old 06-14-2016, 07:18 AM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,768
I am not a SPICA expert. Retarded ignition could cause your problem. At 5000 rpm the timing light should show the "M" mark aligned with the pointer. The ID405 has a different advance curve from the one that was originally fitted to your car so setting the advance at idle might be the source of your problem. I would call Centerline and ask them how to set it up. They may recommend a different max advance from the one on your pulley.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is online now  
post #5 of 11 (permalink) Old 06-15-2016, 03:16 PM
Registered User
 
61SS's Avatar
 
Join Date: Nov 2007
Location: Boiling Springs (Carlisle) PA USA
Posts: 279
Quote:
Originally Posted by ihart View Post
Thanks Ed, I forgot to mention that the coil is brand new. It is a Bosch Blue coil. I did not add back in the resistor that was on the 42 year old original coil.
Just a heads up that a buddy of mine just bought a brand new Bosch Blue that turned out to be faulty. It ran fine for something like 40 miles but if I recall at that point the car would not start at all.

Hard to say, but the fact that it is becoming more frequent says to me that it is not something like a programmed advance curve which would not have changed and more likely something like a deteriorating coil or wire or ??

If you still have the original coil and distributor you could revert to those and see what happens.

Last edited by 61SS; 06-15-2016 at 03:19 PM.
61SS is online now  
post #6 of 11 (permalink) Old 06-15-2016, 05:15 PM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,768
Quote:
Just a heads up that a buddy of mine just bought a brand new Bosch Blue that turned out to be faulty. It ran fine for something like 40 miles but if I recall at that point the car would not start at all.
I too know of one that failed after a short time. There is a suggestion that the bad ones were made in Brazil.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is online now  
post #7 of 11 (permalink) Old 06-15-2016, 07:49 PM
Moderator
Platinum SubscriberModerator
 
Alfajay's Avatar
 
Join Date: Jan 2005
Location: San Juan Capistrano
Posts: 9,807
Quote:
Originally Posted by ihart View Post
Does this smell like a distributor/spark problem and not a SPICA issue of some sort?
Yes, if only because the ignition was the last thing you changed - it would be quite a coincidence to have the Spica start acting up right after a new distributor was installed. Did you have conventional points before?

I like the bad sparkplug wires theory. If your wires are old, the hotter spark of the electronic ignition may have killed them. I also like the defective coil theory. Question: Is a Bosch blue coil compatible with the Centerline ID405 distributor? If not, that may be what has killed it.

Quote:
Could it be that I timed the distributor at the idle "P" mark rather than at the 5000 RPM "M" mark?
It is better to time to the "M" mark - maximum advance is more critical than idle advance. But sub-optimal timing wouldn't cause a sudden loss of power at 3,200 rpm.

Quote:
Originally Posted by 61SS
If you still have the original coil and distributor you could revert to those and see what happens.
I would begin by replacing the plug wires (assuming they are old). This is good preventative maintenance, especially when converting to a hotter ignition. If that doesn't solve it, I would do what 61SS advises, and swap back to the old distributor and coil. If that doesn't solve it, then maybe it is a Spica issue.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 06-15-2016 at 08:01 PM.
Alfajay is offline  
post #8 of 11 (permalink) Old 06-16-2016, 04:02 AM Thread Starter
Registered User
 
Join Date: Sep 2015
Location: Newton, MA USA
Posts: 46
Garage
Thanks for all the suggestions. I liked the coil theory. I woke early today and swapped back in the old coil.

No fix.

The behavior is easily reproducible now while parked. If I sit in the drivers seat and rev the engine over around 3200 RPM, the engine runs but it is hesitating and struggling even as I go to 4500 RPM.
It seems fine under around 3200 RPM.

I will place a Centerline order for a new set of spark plug wires.
ihart is offline  
post #9 of 11 (permalink) Old 06-16-2016, 05:14 AM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,768
The Bosch Blue coil is compatible with the Centerline dizzy. Sub optimal timing may not cause your problem but grossly retarded timing would. If you revved the motor and the "P" mark was at the pointer with the timing light then it is grossly retarded.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is online now  
post #10 of 11 (permalink) Old 06-20-2016, 06:38 AM Thread Starter
Registered User
 
Join Date: Sep 2015
Location: Newton, MA USA
Posts: 46
Garage
Problem solved!

I put in the new Centerline spark plug wires yesterday as an attempted fix. NO FIX. They are high quality wires and for $31, a good replacement for the old ones anyway.

I got out the timing light, set it up on the plug 1 wire and rev'ed the engine past 3200 RPM. I immediately noticed the strobe light shutting off. I now knew it was some kind of spark issue.
After thinking about it for a while, I went over to the distributor and tried to twist it. It was totally loose....

When I installed the new distributor a few months ago, I must not have tightened it enough. The problem seemed to get worse over time because it rotated more out of timing as the weeks went by.

I re-timed it up and snugged the distributor nut down. The test drive was rewarding to the poor mechanic that did the original shoddy work.

Thanks to the forum for the debug help.

Last edited by ihart; 06-20-2016 at 06:53 AM.
ihart is offline  
post #11 of 11 (permalink) Old 06-20-2016, 08:08 AM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,768
Great. The distributor turns clockwise when it gets loose and retards the ignition.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is online now  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Alfa Romeo Bulletin Board & Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome