Low RPM Hesitation/Stumble

[H311RA151N]

In the winter, long before I did my manual transmission swap, I replaced the distributor seal. Upon initial start up after reassembly it had a really bad miss and it would stumble fairly hard up until about 2000 RPM's. It would worsen as the accelerator was pressed and would lessen as the accelerator was released. I figured it was due to the ignition timing being off.

Yesterday I did the following:

-Replaced the TPS. Set the TPS at exactly .45 volts closed. Reset the ECU.

-Cleaned, tested and re-installed IACV.

-Bleed the coolant system.

-Replaced the spark plug wires with NGK wires.

-Set the base idle properly at 700-800 RPM's.

-Put the ECU into base ignition timing mode then set the base ignition timing at what I believe to be perfect or near perfect (15* mark).

-Reset the ECU.

The condition has improved as it now takes more accelerator pressure at a lower RPM to make it miss. But the miss is still just as bad when it does it.

After preforming the manual transmission swap I had three CEL's on initial start up. 12, 14, 41.

12 was due to the vacuum line on the EGR valve being cracked. This was fixed immediately.

14 was due to the IACV being unplugged. I did this and I forget why now.

41 was due to being ran briefly with no downpipe after the manual transmission conversion to ensure the procedure was preformed correctly. On my F22A4 the oxygen sensor is in the downpipe so there was no oxygen sensor at that time.

There are no CEL's currently and I have put 100 miles on the car since resetting the ECU for the final time yesterday.

I know the fuel filter is due to be changed as well as the spark plugs. However I don't think this is the issue.

I'm thinking it may be a weak coil or possibly something incorrect in the distributor although I'm fairly certain I did in fact do it correctly.

I was wondering if anyone had any idea as to what this may be. I apologize if this is to much information, I tend to do that.

[cb9love]

When you were rebuilding your distributor did you change the ignitor, Often times a failing ignitor will cause rpm stumble. I;ve had new aftermarket ignitors fail from the store.
The best replacement ignitor i found was inside of a oem distributor. Other than that check your coil like you thought of.
Only thing is when i experienced it it was at high rpm not low rpm, doesnt mean yours isn't failing differently.

[H311RA151N]

When you were rebuilding your distributor did you change the ignitor, Often times a failing ignitor will cause rpm stumble. I;ve had new aftermarket ignitors fail from the store.
The best replacement ignitor i found was inside of a oem distributor. Other than that check your coil like you thought of.
Only thing is when i experienced it it was at high rpm not low rpm, doesnt mean yours isn't failing differently.

I did not change the ignitor.

I have had ignitors fail in the past. As I recall this is the 5th CB I have owned. But honestly I forgot about ignitor failure... I have several spare ignitors laying around that I know are good. I may change the current out when I do the coil just to do it.


But now that I typed the above and I think about it, previously when I have had ignitors fail the car "shuts off" and doesn't miss. It's like you turned the key off then a few seconds later while the car is still in gear turned the key back to the on position, firing the engine back up. Normally after a few days of doing this, the car would "shut off" not start until replacing the ignitor.

When your ignitors failed did yours respond in the same way? Or did they miss?

[cb9love]

when my ignitor was failing it was a sputter or miss , it did not shut on and off or shut down.
I figured out it was the ignitor from another post about a bouncing tach that didn't correspond to the motor rpm's

[H311RA151N]

when my ignitor was failing it was a sputter or miss , it did not shut on and off or shut down.
I figured out it was the ignitor from another post about a bouncing tach that didn't correspond to the motor rpm's

Ok, well thank you for your help! I have never had an ignitor fail that way.

They did however cause the tachometer to go nuts at the same time the car would shut off and come back on. I don't think mine is doing that this time though.

I will change the ingitor and coil out today and I'll go from there.

[H311RA151N]

Never got around to changing out the ignitor or the coil. However, I changed the plugs and now it doesn't do it.

The plugs were probably at about 1/8" gap. Needed replaced for a long time. I'm betting I have a weak coil.