Pulsing / surging Baja engine

Technical Discussions - Got a mechanical problem?

Moderator: bajabob

Post Reply
amuraivel
Scoobytruck Lurker
Posts: 2
Joined: Tue Dec 03, 2019 7:51 am

Pulsing / surging Baja engine

Post by amuraivel »

Dear Baja Owners,

I'm new to the club, but really like the car (truck?) so far. My Baja, a 2005 SportShift Turbo, has been sitting for a while. The engine seems to "pulsate" throb or surge with perfect throttle. That is to say under steady throttle, the car will rev up to 1200 rpm then back down to 900, then up again, to 1200 then back down to 900. It slightly affects the speed of the car, which is still more or less drivable.

The Subie dealership thought it was the throttle body, and cleaned it -- but it didn't solve the problem.

Has Anyone had this problem or know the solution?
User avatar
kamesama980
Scoobytruck Master
Posts: 369
Joined: Mon Feb 29, 2016 6:54 am

Re: Pulsing / surging Baja engine

Post by kamesama980 »

Since this is your first post, we don't know much about you. Do you have much skill or many tools for working on the car? How about electronics (where the problem likely lies)?

Other than this issue, does it make power? fuel economy within normal?
Any mods or is it stock?
Maintenance up to date? All the fluids changed?
Any check engine light?
Any recent work done?
Does it do this when you're stationary or driving? What speed? One gear or all gears?
When the RPMs drop, is it smooth like the throttle is closing or ragged like a misfire?

If you can read the ECM live data, graph the accelerator pedal position vs Throttle position.
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
TrentRoogna
Scoobytruck Contributer
Posts: 20
Joined: Sat Jul 27, 2019 7:11 pm

Re: Pulsing / surging Baja engine

Post by TrentRoogna »

This is gonna sound silly, and the issue prolly wasn't a factor in what eventually happened; but
The '99 outback I had in high school had a similar issue. It idled 800ish high, then would chill out after about 30 seconds, then spike back up. I never found out what caused it.
That car eventually died to a cracked engine block from a failed radiator (high school me didn't notice some obvious signs).

I have no evidence that there was any connection between the issue and the failure. Logically, I suspect they weren't related at all.

But failing any good ideas, it's something to check if you can do so affordably.

------
Edit: The post above that came through while I was typing has much better ideas.
amuraivel
Scoobytruck Lurker
Posts: 2
Joined: Tue Dec 03, 2019 7:51 am

Re: Pulsing / surging Baja engine

Post by amuraivel »

Since this is your first post, we don't know much about you.

> Do you have much skill or many tools for working on the car?

After binging car videos on YouTube for 3 months I have very good understanding, but 0 time with a wrench, and 0 tools...

> How about electronics (where the problem likely lies)?

I think they're good. Everything works in the car except the windshield wiper pump, which I need remove and test.


> Other than this issue, does it make power?

Yes, the car is very zippy, and after taking delivery, I know I don't want to put crazy horsepower into it because it's already almost enough to "get me into trouble" since it will be my daily driver.

> fuel economy within normal?

It drinks fuel from what I can tell.


> Any mods or is it stock?
Stock.

> Maintenance up to date?
> Any recent work done?

Yes, I had the official Subaru dealer inspect and do any outstanding maintenance.
They replaced the rusted brakes and some hoses.

> All the fluids changed?

They should be, but I shall put this on my to-do list.

> Any check engine light?

Yes, the dealer charged me about 20 bucks to tell me the error code is the front O2 sensor -- so I've ordered another.
And another 50 to clean the throttle -- which was supposedly the cause -- but it didn't work......

> Does it do this when you're stationary or driving?

When driving around town.

> What speed?

ca. 20-50.

> One gear or all gears?

Noticeable in 2nd and 3rd.

> When the RPMs drop, is it smooth like the throttle is closing or ragged like a misfire?

It's smooth like someone is opening and shutting the throttle.

> If you can read the ECM live data, graph the accelerator pedal position vs Throttle position.

I can't, I'd like to get a Cobb access port to read the engine data, but apparently the Baja isn't supported.
I know there are other readers, but it seems a bit hit and miss on the coverage of the data.
User avatar
kamesama980
Scoobytruck Master
Posts: 369
Joined: Mon Feb 29, 2016 6:54 am

Re: Pulsing / surging Baja engine

Post by kamesama980 »

a generic OBD2 to bluetooth reader and the torque app on your phone would be enough to read live data.
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
joedavex
Scoobytruck Contributer
Posts: 45
Joined: Tue Apr 23, 2019 9:29 am
Location: NW CT

Re: Pulsing / surging Baja engine

Post by joedavex »

I've had great luck with the $10 bluetooth OBD2 readers from Amazon and spending the $5 for Torque Pro. Highly recommended for tracking down this kind of problem.
Gray 05 Turbo AT
Silver 04 Turbo AT
Black 04 Turbo AT
and assorted other vehicles....
Post Reply