Here is a pattern we see a lot on small, focused accounts. The Google Ads campaign spends for a while, then quietly stops spending. The owner lowers the Target ROAS to coax it back, delivery recovers for a bit, then it flatlines again. On a chart it looks like a heart monitor: spikes, then a flat line, then another spike.
The instinct is to blame the budget, the keywords, or the algorithm. Usually it's none of those. The campaign isn't failing. It's starving.
What Target ROAS is actually doing
Target ROAS is value-based Smart Bidding (Google now labels it simply "Target ROAS", formerly "Maximize conversion value with a Target ROAS"). You hand Google a return on ad spend target, and it only bids into auctions where it predicts it can hit that return. To make that prediction it needs a steady stream of conversions with values attached to learn from.
Google's minimum for Target ROAS on Search and Shopping is 15 conversions in the past 30 days, and in practice value bidding is far steadier with several times that. A niche, bottom-of-funnel campaign, the kind selling into a small, specific audience, often produces a fraction of that. There simply isn't enough signal for the model to work with.
The death spiral
Now add a normal quiet stretch. Even a healthy low-volume campaign will have a week or two with no conversions, just noise. To Target ROAS, that stretch reads as "this campaign is no longer hitting its return." So Google does exactly what you told it to: it protects the target by lowering bids and pulling back delivery.
Less delivery means fewer impressions and clicks. Fewer clicks means fewer conversions. Fewer conversions makes the campaign look worse, so Google pulls back further. That is the spiral, and each loop down is harder to climb out of than the last.
One thing that does not explain it: Google's August 17, 2026 bidding update. That change applies to campaigns that are limited by budget, and it makes them deliver closer to their target instead of overperforming it. A campaign that stalls below its budget is not budget-limited, so the update does not touch it. This is a volume problem, not a budget one.
Why lowering the target makes it worse
The common fix, nudging the ROAS target down whenever it stalls, is the one that keeps you stuck. Changing the target is a bid strategy change, which Google lists as a trigger for the learning period. So every time you touch it, the campaign re-enters learning with the same thin data it had before. You are treating the symptom (the output number) while the cause (too little conversion volume) never changes.
The fix, on the same budget
You don't need more money. You need to give the algorithm something to learn from.
- Optimize to a more frequent signal. Don't point the campaign only at the rare bottom-funnel event. Count an earlier, higher-frequency action too, a sign-up or a product activation, so there's a steady flow of conversions to learn from. Assign values (a purchase worth more than an activation, an activation more than a sign-up) so the important actions still carry the most weight. This is the single biggest lever.
- Match the strategy to your volume. If you genuinely can't feed a value target, don't run one. Maximize conversions asks for no target at all, which is exactly why it's the safer home for a low-volume campaign. Chase conversions first; add a target later, once volume lets you set that number honestly.
- Then stop touching the target. Set it and leave it long enough for learning to complete. Every change restarts the clock.
Do that and the shape changes. Instead of a flatline punctuated by panic edits, the campaign gets a consistent enough stream of signal to hold delivery steady on the budget it already had.
The takeaways
- A Target ROAS campaign that spends then stalls is usually starving for conversion volume, not failing.
- Value-based Smart Bidding needs a steady stream of conversions (Google's floor is 15 in 30 days on Search; more is far steadier); a niche campaign rarely produces that.
- A quiet week reads as failure, so Google throttles delivery to protect the target, which starves it further.
- Lowering the target restarts the learning period every time. Fix the input instead: optimize to a more frequent conversion action, or run Maximize conversions with no target.
Common questions
Why does my Target ROAS campaign stop spending?
Target ROAS is value-based Smart Bidding: Google only bids when it predicts it can hit your return target. On a low-volume campaign, a week or two with no conversions reads as the campaign failing, so Google lowers bids and delivery to protect the target. Less delivery means fewer clicks and fewer conversions, so the pullback deepens. It is starving, not failing.
How many conversions does Target ROAS need?
Google's minimum for Target ROAS on Search and Shopping is 15 conversions in the past 30 days, and in practice value-based bidding is far steadier with several times that. A niche, bottom-of-funnel campaign often produces a fraction of that, which is why the strategy never stabilizes. The number is guidance, not a hard gate, but the direction is real: too little volume and the algorithm cannot learn.
Should I lower the ROAS target when the campaign stalls?
It is the common reflex and it makes things worse. Changing the target is a bid strategy change that Google lists as a learning-period trigger, so the campaign never settles. Repeatedly lowering the target just keeps it in a permanent relearning loop. Fix the input, the conversion volume, instead of chasing the output.
How do you fix a low-volume Target ROAS campaign?
Give the algorithm more to learn from. Optimize to an earlier, more frequent conversion action such as a sign-up or activation rather than only the rare purchase, and assign values so the important actions still weigh most. If you cannot feed a value target honestly, switch to Maximize conversions, which asks for no target at all. Then leave the target alone so learning can complete.