Google Performance Max for E-commerce: Common Pitfalls and How to Avoid Them

Are your PMax campaigns driving real growth, or just looking good on paper?

Google’s Performance Max provides e-commerce brands with massive reach and automation superpowers, but only when guided by strategy and structure. Left alone, it can waste budget, hide key data, and prioritize the wrong products.

Let’s examine the most common PMax pitfalls and the precise steps to avoid them, enabling you to unlock stronger ROI and smarter, more predictable performance.

1: Neglecting the Product Feed

A weak or incomplete feed limits visibility and relevance. Missing basics like price, availability, or strong images can stop products from serving. PMax relies on your Merchant Center feed to understand what you sell, and Google flags any content that doesn’t meet its rules.

Here’s how to avoid this pitfall and strengthen your feed:

• High-Quality Images: Use 500 × 500 pixels or higher to unlock more placements, including YouTube Shopping ads on CTV.
• Clean, Updated Data: Keep price, stock, and availability current with a strict 1:1 match to your landing page.
• Optimized Titles & Descriptions: Add clear titles and rich descriptions to help Google match search intent. 
• Full Required Attributes: Include ID, price, availability, and image links to prevent disapprovals.
• Smart Custom Labels: Tag items like “bestseller” or “high-priority” for better control and segmentation.

2: Poor Campaign and Asset Group Structure

When everything lives in a single giant PMax campaign, Google struggles to determine what to show and when. Unrelated products blur the data, slow spending, and weaken performance.

Here’s how to avoid this issue and build a more transparent structure:

• Segment Campaigns Wisely: Group products by type, performance, or margin to provide Google with clearer signals.
• Create Focused Asset Groups: Keep themes concise so that images, videos, and text align with the products within each group. PMax allows up to 100 asset groups per campaign. 
• Use Smart Custom Labels: Tag items like “seasonal,” “bestseller,” or “high-margin” to organize your structure.
• Allocate Budgets Intentionally: Fuel your most important groups so Google learns faster and drives stronger results.

3: Ignoring Brand Exclusions

When PMax displays ads featuring your brand name, your results may appear stronger than they actually are. These easy wins can also take credit away from your Search campaigns, making it harder to see what’s actually driving sales.

Here’s how you can avoid this problem and keep your data honest: 

• Add Brand Exclusions: Use account-level negative keywords to block branded traffic across all campaigns. Google allows up to 1,000 negative keywords at the account level. 
• Keep Brand Search Separate: Run brand terms in their own campaigns for full control over bidding and reporting.
• Track Real Performance: Review PMax without brand traffic to understand the true growth of new customers.

4: Not Giving the Algorithm Enough Time or Data

If you change budgets or settings too fast, the system can’t recognize patterns or make smart bidding decisions. PMax optimization depends on machine learning, which needs time and sufficient data. 

Here’s how you can avoid this issue and help the algorithm learn: 

• Give It Time: Run your campaign for at least 6 weeks before making changes so Google’s AI has enough time to learn patterns and stabilize.
• Check Your Tracking: Ensure that every conversion is accurately recorded. Clean, accurate data is the fuel PMax needs to optimize your bids.
• Start Broad With Bidding: Use Maximize Conversions at first, since Google’s AI adjusts bids at auction time and learns best with fewer limits.
• Keep Your Budget Steady: Maintain a stable daily budget so the system has consistent signals to work with. 

5: Over-Relying on Automation

PMax is powerful, but without direction, it can push your ads onto low-value sites or generate creatives that don’t match your brand. Because Google’s AI controls placements and can auto-build assets, your budget can disappear fast if you don’t stay involved.

Here’s how you can stay in control while still using automation well: 

• Use Your Own Creative: Upload branded images, videos, and copy so you don’t rely on Google’s auto-generated assets, which can feel off-brand or highlight the wrong products.
• Watch Your Placement Insights: Check where your ads appeared and review audience performance to identify and address low-value placements early.
• Exclude Irrelevant Sites: Use account-level placement exclusions to block risky or low-quality inventory. Google allows up to 65,000 placement exclusions per account.
• Use URL Expansion Carefully: Turn it on only when you’re sure your landing pages are strong to avoid sending users to weak or irrelevant URLs.

6: The “Black Sweater Problem” — Product Dominance

When one best-seller grabs most of your impressions, the rest of your catalog fades into the background. This “black sweater” effect shrinks your visibility and stalls growth. Google notes that without a clear structure, PMax will keep pushing the same winner on repeat.

Here’s how you can prevent one product from taking over your campaign: 

• Split Strong Performers: Move top sellers into their own campaigns or asset groups. Use custom labels to mark bestsellers, seasonal items, or underperformers, so Google has clearer signals to work with.
• Watch Your Visibility: Check your impression share in listing groups and shift your budget toward SKUs that deserve more exposure. Google allows up to 5 custom labels, so use them wisely.
• Audit Often: Review performance regularly. A quick check of product-level data helps you catch dominance issues before they cannibalize the rest of your catalog.

7: Limited Control and Data Transparency

PMax hides key details like full placements and impression share, so it’s harder to see what’s truly driving results. Google confirms placement reports only cover some channels, and 10–20% of PMax conversions often come from branded searches, which can inflate results.

Here’s how to stay in control even when PMax keeps things blurry:

• Run Supplemental Standard Shopping or Search Campaigns: Use these to see impression share, search terms, and true non-brand performance. They reveal what PMax can’t.
• Use Google Analytics and UTMs: Track where users actually go and spot hidden trends that PMax reporting doesn’t show.
• Lean on Trend-Level Insights: Since granular data is limited, focus on patterns over time to guide your adjustments.

8: Ignoring Standard Shopping Campaigns

Many brands turn off Standard Shopping after launching PMax, but that move cuts your control and visibility. PMax needs 20–30 conversions a month to learn. Without that, it leans on broad or branded traffic that distorts performance. Standard Shopping fills the gaps with cleaner data, tighter targeting, and real control over bids and queries.

Here’s how you can avoid this mistake and keep both campaign types working in your favor:

• Use Both Together: Let PMax handle discovery while Standard Shopping controls high-intent traffic and branded searches.
• Test Product Groups: Run items separately in each campaign type to see where they truly perform best.
• Balance Budgets: Monitor shifts where PMax cannibalizes Standard Shopping, and adjust spending so both campaigns remain strong.

9: Focusing on ROAS Alone Instead of Profitability

PMax loves easy wins, and ROAS makes them look great. However, a high ROAS doesn’t necessarily translate to high profit. Low-margin items can drain your budget while true moneymakers barely show up.

Custom labels enables you to tag products by margin, and value-based bidding performs best when you give Google real profit or proxy values. With the right signals, the system optimizes for revenue that actually matters.

Here’s how you can avoid it and shift your campaigns toward actual profit growth:

• Segment Products by Margin Category: Use custom labels to separate high-margin, low-margin, and clearance items.
• Track Gross Profit per Conversion: Watch profit contributions, not just return percentages.
• Adjust Bidding and Budgeting Based on Profit: Set targets around value and allow flexible budgets so Google’s AI can prioritize the products that deliver real gains.

10: Overlooking Creative Quality and Relevance

Weak or generic creative slows your entire PMax campaign. Google’s system relies on your images, videos, and text to create high-performing combinations, and low-quality assets make it trickier for the algorithm to learn. PMax works best when you add plenty of high-quality assets and refresh creative often. 

Here’s how to avoid this pitfall and keep performance high:

• Provide Branded Videos and Lifestyle Images: Rely on your own visuals instead of auto-generated ones.
• Test Variations of Copy and Visuals: More assets unlock more combinations, helping Google learn faster.
• Ensure Visuals Match Your USP: Keep creatives aligned with your landing page so users get a clear, consistent story.

Your PMax Future Starts Here

Performance Max becomes a growth engine when you guide it with a clear structure and wise choices. Avoid these pitfalls, and you’ll run campaigns that not only perform well today but will keep getting stronger.

You’ve got everything you need to steer PMax with confidence. Now push forward and let the wins compound. 

FAQs

How long should I let my Performance Max campaign run before making changes?

Let it run at least 6 weeks so Google’s AI can learn patterns and stabilize performance.

Should I still run Standard Shopping campaigns alongside Performance Max?

Yes. Standard Shopping provides you with tighter control, more precise data, and helps balance PMax’s broad automation capabilities.

How do I prevent one product from dominating my Performance Max campaign?

Split top performers into separate campaigns or asset groups and monitor impression share to rebalance visibility.

What are the most important product feed elements to optimize first?

Start with high-quality images, up-to-date prices and availability, strong titles, and all required attributes.

How can I tell if my PMax campaign is cannibalizing branded search traffic?

Check performance without brand terms by using brand exclusions and reviewing results in your separate brand Search campaigns.