Surging while cruising/constant speed
 

8K on new engine (reman installed by Mazda) Car has 92K.
SSV removed and cleaned by Mazda at engine install. Previous to that I removed it at 71K and cleaned it.
Coils, plugs, wires, fuel pump, radiator fans all have 8K or less on them.
MAF and ECS sensors cleaned.
Battery posts cleaned.
No CEL.
Idles fine and accelerates strong.
Adding ¼ oz of 2 stroke oil to every gallon of gas.
I wrapped my AC lines with insulator foam.
Plastic baffles removed from air box.

I have searched for these symptoms and have not been able to find an answer.:banghead:

Symptom: While cruising at any speed in any gear with the AC on there is a constant surge as though I am pulling a trailer. It is not the cycling of the compressor. The AC works fine in 100 degree outside temps.

I greatly appreciate any help with a resolve.

Nice write up...
But you forgot one thing .. Auto or MT?

I'm still inclined to think it's your AC compressor ...
Other thoughts are clutch is slipping or the Auto trans is slipping

Missed it in the write up, but it is in my Signature......MT, No slush box.
The AC compressor seems to be working properly. The air temp coming out is good (checked with gauge), the freon level is good (checked with gauge) and the cycle times are within standard operation.
The clutch is not slipping under a load or under acceleration.

OOps .. sorry missed ur sig

Well mmmmm you say it only happens with the AC on sooo uh

Well I've got low compression on my engine and I can feel when the compressor cycles on during cruise. I know you've got a new motor, I'm just thinking out loud.

I guess you could also have a worn TB Sensor, thinking that under the extra load of the AC puts it in that perfect (or broken) spot to create an issue during cruise.

But does it 'surge' with the AC switched off? Does the cruise control hold a constant speed? A cycling AC will cause the cruise control to open/close the throttle slightly to compansate for the load. If it's doing it a lot now, compared to before the new engine, I'd suspect that that refridgerant has leaked or was not properly filled after the engine swap.

The extra load with the AC makes it noticeable. I am not 100% sure it is not doing it all the time, but can’t define it without the AC. The cruise is not on during this issue. The cruise does hold a constant speed when used. The best description I have is it feels like I am towing a trailer and you experience the feeling of a porpoise lunging in and out of the water.:boink: My guess is it is possibly a vacuum leak. As soon as I give it fuel it smoothes right out with No hesitation. Thanks for all the helping with the diagnosis!

If you have a vacuum leak, it will show up as high (> +10%) Long Term Fuel Trims. I wouln't expect it to result in surging unless it's really extreme.

New development this morning:
The hazard lights were on when I started the car this morning, but the hazard lights were not switched ON. They cut off immediately after the car started on there own:uhh:
The radio presets were there, but the fade, balance, bass, middle and treble went to Zero on there own over night:confused:

Battery tested Charge required 498 CCA should be 605 CCA
Starter tested normal 10.64 volts with 1 second interval
Alternator/charging system tested no issues NO LOAD @ 13.78 volts and with LOAD (everything on) @ 13.91 volts.

What is the normal range of this alternator? Is 13.91 volts under a load high enough?

Step one, charge or replace battery.. Could have a cell going bad. The load / no load numbers are funny. The battery doing funny stuff will piss of the electrical system. That messes with the alternator which will load the engine trying to make things better. If you are going down the highway at 60, in 6th gear, you do not have a lot of power to play with.

Then look at the grounding and clean up stuff in the $100 thread in my sig. Especially since they took the engine out. I have a grounding kit, but am starting to believe that just cleaning the grounds and adding a star washer is enough.

suggest you put them back in and retry .

I removed the Plastic Baffles in the air box 3 years ago. Is there a known issue with them removed?

Bought a new battery and will install it this weekend when I go through all the grounds (adding star washers).

Thanks for the suggestions!

/\ not normally an issue i don't think , but an easy test to put them back in and see if it changes anything ....

1. Changed the Battery to a more powerful Battery 620 CCA and 750 CA
2. Cleaned contact area and put star washers on negative ground from Battery (under air box) and all other grounds in engine compartment
3. Added an additional ground from the Negative Battery post to the strut tower brace
4. Reset AC
5. Reset ECS
6. Reset ECU, KAM and NVRAM
7. Noticed a difference on the start, started up instantly
8. Idle seems more stable
9. WOW!

Will update on surging issue as I drive it.......Thanks for all the help and input!

If by chance it still surges, don't forget to look into the "TPS", but hopefully you got it.

Thank you thank you thank you
:wallbash:

I thought I was losing my mind

Nah, I think it was much earlier than that, back when you thought I was driving an AT.......:rollingla

So far the engine feels like the day I bought it with 14 miles on it....... way back when! No more......:boink:
Thanks again for all the suggestions!

Sounds a bit low, should be 14.25 to 14.50. Have you tested the rate with the new battery?

I have not tested it, but I will.
I am amazed at the increased throttle response and the smoothness. No more :boink: going through the gears or at cruising speeds. It is so different to drive, I did not know how bad it really was performing.

Oddly enough it is 13.64 with the new battery and adding more ground?

Have you checked/adjusted the alternator belt tension? If so, I think you should have the alternator bench tested to insure your original problem doesn't return.

I will check the belt and tension, my bride said sometime she hears a "squeaking like a belt". The battery was a 75 month battery that Mazda put in with the new started and reflash back in 2006. It was 69 months old, so the battery needed to be replaced anyway. Will bench test the alternator as well! Thanks for the advice!